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*
Sidney Kimmel Cancer Center, San Diego, CA 92121; and
Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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It has long been considered that B cells have an important, although not obligatory, role as APC for primary CD4 responses. In vitro studies have clearly shown that activated B cells are nearly as effective as dendritic cells (DC)4 in their capacity to activate naive CD4 cells (3). Although primary CD4 cell responses can develop in mice that genetically lack B cells (4, 5, 6, 7, 8, 9), depletion of B cells from normal mice can reduce the magnitude of the response, implying that B cells may contribute to the level of T cell priming (10, 11, 12, 13). Recent reports confirm that Ag-bearing B cells induce naive CD4 cell proliferation in vivo (14, 15), and studies of the progressive migration of subsets of cells within lymphoid tissue during the CD4 response to Ag indirectly support a hypothesis that precisely regulated interactions with APC influence the magnitude of the response (14, 16, 17, 18).
DC that localize in the T cell zones are the primary APC for the initial expansion of naive CD4 cells (19). Naive B cells are also transiently found in the T cell zone as they migrate to the follicles or B cell areas (16, 18). After Ag exposure, B cells expand in the T cell zone where CD4 memory cells appear to primarily arise (20) and the response then proceeds to the follicle (18). Either engagement of the B cell receptor (BCR) by Ag (21, 22) or ligation of CD40 by CD40 ligand (CD154) expressed on activated T cells (23) can rapidly elicit expression of B7-2 (CD86) on B cells which would enable them to provide costimulation for naive CD4 cells. Thus, although CD4 cells may first encounter Ag presented on DC, shortly after a response is underway, B cells could become competent APC. As Ag-specific B cells proliferate, a bias toward usage of B cells as APC by the expanding T cell population in the face of limiting numbers of DC would likely occur, providing a means to sustain further proliferation of both T and B cells engaged in the response.
Since the extent of CD4 cell expansion during a primary response might impact the development of a persistent memory population, we asked whether B cells have an essential role for the development of memory CD4 cells using B cell-deficient mice. Our results indicate that although CD4 cell priming occurred in the absence of B cells, there were significantly lower frequencies of both primary and memory Ag-specific cells. The deficiency was unaffected by boosting with Ag under conditions that favor CD4 cell priming via DC (24, 25), but was completely reconstituted when B cells were provided. Moreover, B cells activated in vitro with IL-4 and either cognate or noncognate Ag could also restore CD4 priming in B cell-deficient mice. The results provide direct evidence that B cells are necessary for the optimal development of memory in the CD4 population by regulating the magnitude of the primary CD4 cell response independently of Ag presentation.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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C57BL/6 mice were bred at The Scripps Research Institute. C57BL/6 Igh-6 µMT (Ig µ chain knockout) mice (26) were purchased from The Jackson Laboratory (Bar Harbor, ME).
Abs and Ags
mAb for the depletion of T and B cells were generated and
purified as previously described (27). These included
anti-Thy 1.2 (HO13.14, F7D5), -CD8 (3.155), -CD4 (RL172.4), -B220
(RA36B2),-DC (33D1), -J11d, anti-class II (CA-4.A12,
anti-I-Ab/d/k), and mouse anti-rat 
chain (MAR.18). FITC-antimouse ,
-anti-IAb, -B7-2, -CD40, -ICAM-1, -LFA-1, and
PE-anti-B220, -CD4, and -Thy 1.1 were purchased from PharMingen (La
Jolla, CA). Keyhole limpet hemocyanin (KLH) was purchased from
Calbiochem (La Jolla, CA) and OVA was obtained from Sigma (St. Louis,
MO). For pulsing of B cells, KLH and OVA were conjugated with
4-hydroxy-3-nitrophenyl acetyl (NP; Cambridge Research Biochemicals,
Valley Stream, NY) (28).
B cell and DC isolation and immunizations
To reconstitute B cell-deficient mice, 
light chain-bearing B
cells were isolated from a preparation of negatively enriched splenic B
cells (Stem Cell Technologies, Vancouver, Canada) by sorting for
-B220+ cells with a
FACS Vantage flow cytometer (Becton Dickinson, Mountain View, CA).
These cells were pulsed by overnight culture with NP-KLH or NP-OVA at
100 µg/ml in RPMI 1640 media (Irvine Scientific, Santa Ana, CA)
containing 7% FCS (HyClone, Logan, UT), 200 µg/ml penicillin, 200
U/ml streptomycin, 4 mM L-glutamine, 10 mM HEPES, and
5 x 10-5 M 2-ME, and supplemented with 10
ng/ml r IL-4. Two x 106 freshly isolated or
Ag pulsed, + B cells were injected i.v. into
recipient mice that were either unprimed or immunized 1 day earlier by
i.p. injection of 100 µg KLH precipitated with alum and combined with
Bordetella pertussis vaccine organisms as described
previously(29). Splenic DC were isolated by magnetic
separation from C57BL/6 or µMT mice using negative selection with a
cocktail of mAb from Stem Cell Technologies that included anti-CD3,
-CD4, -CD8, -B220, -Gr-1, and -TER mAb according to the manufacturer’s
instructions. There was <1% B cell contamination in DC preparations
from C57BL/6 mice. DC were pulsed by overnight culture with 100 µg/ml
KLH or NP-KLH, and 2–5 x 105 were injected
into recipient mice.
In vitro responses of CD4 cells
CD4 cells were enriched from spleens at various times after immunization by cytotoxic depletion with anti-CD8 mAb and panning on 150-mm plates (Fisher Scientific, Pittsburgh, PA) coated with polyclonal goat anti-mouse IgG (H + L specific; Fisher Biotech). The resulting populations were 70% CD4+ cells. For in vitro restimulation of CD4 cells, APC were spleen cells from normal C57BL/6 mice that were pulsed overnight with 100 µg/ml KLH in the presence of 10 µg/ml dextran sulfate and 5 µg/ml LPS (Difco, Detroit, MI) to induce activation, followed by treatment with 25 µg/ml mitomycin C (Sigma) as described previously (28). Viable CD4 cells enriched from lymphoid tissues of KLH-primed mice were quantitated by flow cytometry using PE-anti-CD4 and cultured at the concentrations indicated in the text in triplicate in 250 µl in 96-well flat-bottom plates (Costar, Cambridge, MA) with 2 x 105 KLH-pulsed APC. Limiting dilution analysis (LDA) was performed as previously described (30, 31) by plating serial 1.5-fold dilutions of viable CD4 cells in 36-well replicates with KLH-pulsed APC. To evaluate IL-2 production, culture supernatants were harvested at 36 h and 25-µl volumes from individual wells were tested for the presence of IL-2 by measuring proliferation of the NK-3 cell line (32) as previously described (31). The bioassay is specific for IL-2 when IL-4 is blocked by anti-IL-4 mAb (11B11). IL-2 was quantitated by comparison of test supernatants to standard curves generated with recombinant cytokines (R&D Systems, Minneapolis, MN). The sensitivity of detection for IL-2 is 0.2 pg/ml. For LDA, wells giving cpm values of >3 SDs above the mean of values obtained from 36 wells containing APC only were considered positive. Frequencies were calculated using maximum likelihood analysis (33).
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Despite convincing evidence that activated B cells are competent APC for naive T cells both in vitro and in vivo, the importance of the APC function of B cells in vivo has been widely debated in part because of conflicting data from a number of different models. In particular, studies of B cell-deficient mice, µMT mice that have a targeted deletion of the µ region (26) or mice in which the JH region (JHD) (34) of the IgM locus is disrupted, suggest both that B cells are completely unnecessary as APC for primary CD4 cell responses, as measured by proliferation and cytokine production to protein (4, 5) and viral (9) Ag, and that B cells are necessary as APC for protein (35) but not peptide Ag (36) and for responses to some parasites (37). To assess the requirement of B cells in the development of memory CD4 cells in vivo, we initially compared CD4 responses to KLH in µMT mice vs normal C57BL/6 mice over a 3-mo time period.
As shown in Fig. 1
, CD4 cells from the
spleens of both µMT and control mice responded to i.p. immunization
with KLH and adjuvant as measured by the secretion of IL-2, the
principle cytokine produced in response to restimulation with Ag-pulsed
APC in this model (28, 29). As previously reported, the
absence of B cells did not prevent CD4 cell priming (4, 5, 21). IL-2 secretion at 5 days represents the peak response of
primary effectors (28), whereas that at 3 mo after priming
reflects the Ag recall response of resting memory CD4 cells
(29). However, when we compared levels of cytokine
production by CD4 cells from control and µMT mice, we found that CD4
cells primed in B cell-deficient mice consistently produced lower
levels of IL-2 than did CD4 cells from C57BL/6 controls. The results
suggest that B cells can play a role in priming of CD4 cells.
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revealed that indeed, 5- to 40-fold
fewer Ag-specific CD4 cells producing IL-2 were generated in the
absence of B cells. Moreover, in C57BL/6 mice, frequencies similar to
those found at the peak of the primary response were observed in the
memory population during the 6 mo of observation. A gradual initial
reduction in the number of Ag-specific CD4 cells was evident in µMT
mice, but frequencies then stabilized. Before immunization, frequencies
of IL-2-producing KLH-responsive cells were <1/300,000–1/600,000,
indicating that significant expansion occurred in the CD4 population as
a result of priming with KLH.
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1 cell/well was plated. As
shown in Fig. 3, CD4 cells from
KLH-primed µMT mice produced similar levels of IL-2 per cell
compared with cells from C57BL/6 controls. The average IL-2
secretion/KLH-specific CD4 cell from normal C57BL/6-primed mice
(n = 5) >30 days after priming was 1.36 ± 0.18
pg, whereas the average IL-2 amount from a single cell from matched
µMT mice (n = 5) was 1.66 ± 0.47 pg. The
results indicate that differences in frequency were the primary defect
observed in the CD4 population of µMT mice; although we cannot rule
out the possibility that IL-2 production may be altered in the µMT
model without any effect on the expansion of total KLH-specific CD4
cells.
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), or simply the limitations of the LDA in
detecting all IL-2-secreting cells.
To determine whether the reduced expansion of CD4 cells in µMT mice
could be overcome by multiple immunizations that would result in
repeated exposure of CD4 cells to Ag presented by DC, µMT and control
mice were primed with KLH on three occasions at weekly intervals before
resting for 30 days and evaluation of the frequencies of Ag-specific
cells. The results in Fig. 4 show that
the number of Ag-specific CD4 cells in either µMT or C57BL/6 mice was
not significantly affected by boosting with Ag in adjuvant either once
(data not shown) or twice.
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Previous studies have shown that CD4 cell function in µMT mice
is normal (4, 12). Although priming of µMT mice was
successful, albeit at reduced levels compared with control mice, we
determined whether the Ag-presenting function of DC was impaired in B
cell-deficient mice. This was especially relevant since JHD mice, which
are rendered B cell deficient by disruption of the
JH region of the IgM locus (34), do
have impaired APC/costimulation function that contributes to lower
levels of CD4 priming (35). Therefore, to rule out a
similar condition in µMT mice, we isolated DC from the spleens of
C57BL/6 or µMT mice by magnetic separation, pulsed them with KLH, and
used them to prime normal mice. Under such circumstances, T cell
priming has been shown to be directly induced by Ag-bearing donor DC in
the absence of Ag transfer to host APC (38), which we have
confirmed in our model (data not shown). The results in Fig. 5 demonstrate that irrespective of
whether DC were derived from C57BL/6 or µMT donors, comparable
priming of CD4 cells to KLH was seen at 5 days after immunization as
measured by IL-2 production from bulk cultures. In addition, we found
that the spleens of µMT mice contained similar numbers of DC to
C57BL/6 mice (data not shown). Therefore, DC from µMT mice are not
only present in comparable numbers but also possess a comparable
capacity to present Ag.
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The foregoing results point to a defect in the initial expansion
of CD4 cells resulting in diminished levels of CD4 memory in the
absence of B cells that could not be attributed to defective DC. To
directly assess the role of B cells as APC, we studied the effects of B
cell reconstitution of µMT mice on the CD4 response to KLH. We took
advantage of the well-characterized response of
IgHb mice to the nitrophenyl (NP) hapten in the B
cell population bearing the light chain of Ig (39).
Enrichment of + B cells from these mice
results in the presence of a high FACS sorted frequency of normal,
naive B cells that bind NP (40). We transferred
-bearing B cells into µMT mice immunized with NP-KLH and
determined the frequency of memory CD4 cells 30 days later. Consistent
with our previous findings, the frequency of memory CD4 cells generated
in µMT mice was 
30-fold lower than that in C57BL/6 mice (Fig. 6). As predicted, reconstitution of µMT
mice with B cells enriched for Ag recognition restored the frequency of
memory CD4 cells generated, thus verifying the need for B cells for the
optimal expansion of memory CD4 cells.
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+ B cells were used as a source of
Ag-presenting B cells since a high frequency of these cells bind to the
hapten NP (39, 40). These B cells were pulsed by overnight
culture with NP-KLH in the presence of rIL-4. Treatment with Ag alone
was sufficient to up-regulate costimulatory molecules of B cells, but B
cell survival was vastly improved in the presence of IL-4 which also
contributes to B cell activation (22, 41). By 24 h,
we observed increased expression of class II MHC molecules, CD40 and
B7-2, and adhesion receptors that included LFA-1 (Fig. 7). One day after immunization with KLH
and adjuvant, µMT mice were injected with 2 x
106 NP-KLH-pulsed IL-4-treated
+ B cells. On day 5 (primary effector) or >30
days (memory) after KLH priming, responses of CD4 cells from µMT mice
that did not receive B cells were compared with those from µMT mice
that were reconstituted with B cells and to C57BL/6 controls.
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indicate that
provision of Ag-pulsed activated B cells to µMT mice shortly after
immunization with KLH completely reconstituted the frequencies found in
the primary response as well as the memory response to levels found in
C57BL/6 controls. The results clearly demonstrate that a B cell deficit
can alone account for diminished priming of CD4 cells to KLH, and this
results in a reduced frequency of CD4 cells that persist as memory
cells. Moreover, not only does this system of adoptive transfer
reinforce the findings shown in Fig. 6
but it also enables the
elucidation of the nature of the T-B interaction. Although not shown,
we were unable to achieve a similar level of restoration with freshly
isolated + B cells presumably because few B
cells in the + population would have the
capacity to specifically take up KLH and become activated in vivo.
+ B cells cultured with rIL-4 alone but not
NP-KLH were only minimally able to restore the response of µMT mice
to KLH (data not shown), suggesting that BCR-mediated Ag uptake plays
an important role in activating B cells.
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+ B cells in the spleens of
µMT mice that had received either resting or activated populations by
histological and flow cytometric analysis, and homing of B cells to the
spleen was comparable to that seen in C57BL/6 mice (data not shown). By
fluorescent dye analysis (42), we found that transferred,
Ag-pulsed/activated +B cells divided shortly
after injection into either µMT or control mice. However, B cells
were no longer detected in the spleen by 14 days, suggesting that
rejection had occurred, as reported in other studies (35, 43), or that the transferred B cells either did not survive for
an extended period or did not persist in the spleen once the primary
CD4 response subsided. Thus, the requirement for B cells for optimal
priming of CD4 cells and generation of a persisting high frequency of
memory cells is critical at the early stages of the response. The mechanism by which B cells enhance memory CD4 cell expansion can be envisioned in several ways. B cells can efficiently activate T cells through their ability to capture Ag via the BCR and present peptide in the context of MHC class II molecules to the T cell. Alternatively, activated B cells may interact with T cells through other molecules, such as costimulatory molecules and their ligands, e.g., B7-2/CD28, CD40/CD40 ligand, and/or through other yet to be defined molecules. In the former scenario, T-B interaction would necessitate cognate Ag interaction. However, in the latter case, T-B interaction minimally requires that B cells be activated; thus the requisite for T-B interaction through linked (cognate) recognition of Ag is eliminated. The Ag noncognate interaction between T cells and activated B cells may not be unique to B cells in that other cells, such as DC, may function in a similar capacity.
To test these mechanisms, groups of µMT or control mice were
immunized with KLH in adjuvant and 1 day later
+ B cells pulsed with NP-OVA (noncognate) or
NP-KLH (cognate) in the presence of IL-4 were transferred. One month
after the transfer of B cells, the frequencies of KLH-specific CD4
cells were quantitated. As shown in Fig. 9, B cells that were pulsed with NP-OVA
were as effective as those pulsed with NP-KLH in increasing the
frequency of memory CD4 cells generated in µMT mice. Based on this,
one might predict that the additional transfer of Ag-pulsed DC to the
µMT mice would also be effective in increasing the frequency of
memory CD4 cells. As shown in Fig. 9, this is also the case. Thus, at
the very minimum, further expansion of primed T cells does not require
Ag cognate interactions.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The T-B cell interactions that support CD4 cell expansion need not be linked via recognition of cognate Ag; thus other activated APC have the capacity to serve this function. However, the anatomical location of different APC could preclude them from participating in the response in this role. After Ag stimulation in vivo, activated B cells are present in larger numbers in lymphoid organs than are DC or macrophages, making them the choice candidate for interaction with primed T cells. Moreover, recent studies indicate that DC mature after encounter with inflammatory stimuli and diminish in their ability to function as APC (19). DC also appear to exit lymphoid tissue within 48 h after priming (44), suggesting that the capacity of DC to sustain a CD4 response in situ is limited. Our results provide direct evidence that B cells can be essential for optimal priming of CD4 cells in vivo and that the frequencies of primed CD4 cells generated as a consequence of initial immunization are reflected in a stable pool of long-term memory cells.
Although some reports have failed to detect differences in CD4 priming in C57BL/6 and µMT mice, many in vitro studies suggest that B cells are necessary in addition to DC as APC for optimal priming and responses of CD4 cells (35, 45, 46, 47). Moreover, early in vivo studies showed reduced CD4 cell responses develop when B cells are depleted from normal mice by treatment with anti-IgM Ab (10, 11, 12, 13). More recently, analyses of CD4 responses in B cell-deficient mice have in many instances shown diminished CD4-dependent responses to foreign proteins (35, 36) and pathogens (37). In our model, we show that a much lower response in B cell-deficient mice is not due to a defect in cytokine production per cell but rather to a markedly reduced level of clonal expansion in response to priming. Multiple immunizations with Ag did not elevate the response. Limited CD4 cell expansion could not be attributed to an intrinsic defect in naive CD4 cells (4, 12) or to defective Ag presentation by DC from B cell-deficient mice. However, the transfer of a resting population of naive B cells that contained a high frequency of cells with the capacity for BCR-mediated Ag uptake into B-deficient mice that were subsequently immunized with cognate Ag restored the frequency of IL-2-producing memory CD4 cells. Although the results imply that cognate T-B interactions may be important for optimal CD4 cell priming, we found that B cell reconstitution could be delayed, and we could then explore the requirement for Ag presentation. Our results show that the transfer of activated B cells that were pulsed with Ag either relevant or irrelevant to the CD4 cell response could also reconstitute the frequencies of both primary effectors and persistent memory cells. Furthermore, provision of Ag-pulsed DC after immunization could also restore CD4 cell priming in B cell-deficient mice. These findings demonstrate that the mechanism by which activated APC aid in the expansion of IL-2-producing CD4 cells is not necessarily dependent on TCR engagement via peptide/MHC class II.
Our data support a hypothesis that stimulation of B cells by Ag is important to induce their capacity to support proliferation of responding CD4 cells. Indeed, BCR engagement by Ag promotes the accumulation of B cells in the outer T cell zone where they would be available to interact with responding CD4 cells (48). One can envision that DC become limiting once the expansion phase of the immune response is underway and that an alternative APC population becomes necessary to sustain continued CD4 cell growth. The shift in CD4 cell-APC interactions during the changing conditions of the primary response to B cells as the predominant APC thus provides a means to greatly expand the pool of primary effector cells that are generated. As local concentrations of Ag diminish during the course of the response, it is further possible that Ag-specific B cells would be preferentially used as APC to support continued T cell expansion. Ultimately, the continued decline in Ag concentrations would signal the transition from the acute effector phase to the memory phase of the response.
Since either activated B cells or DC could support CD4 cell expansion when administered after the initial immunization, it is likely that costimulation is the primary deficiency that limits the CD4 response when B cells are absent. Not only are interactions of CD28/B7 molecules necessary for IL-2-dependent CD4 cell expansion, but also for the induction of Bcl-XL which has been shown to maintain T cell survival during the primary response (49, 50). Deprivation of costimulatory signals may thus contribute to a reduction in the initial frequency of primed CD4 cells in B cell-deficient mice through effects on both expansion and survival. However, our findings that a stable low level of memory is maintained over several months and that B cells do not persist in µMT mice do not support a role for B cells in the survival of CD4 memory. Instead, our results are consistent with the recent demonstration that Ag and, for that matter, class II expression do not play a role in memory CD4 cell survival (51). In addition, our data are supported by other recent reports that show that B cells are unnecessary for the maintenance of CD4 memory cells (52). The stability of CD4 memory generated in the presence or absence of B cells suggests that homeostatic mechanisms that are not affected by B cells tightly control the size of the CD4 memory pool.
The results of our study demonstrate that, as has been shown for CD8 cells (53), the initial clonal burst size in the primary response determines the extent of CD4 memory that develops and is then maintained. In our model, an optimal primary effector response translates into a maximal level of memory. Similar results have been reported for CD4 cells after viral immunization (9, 54). The results imply that for CD4 cells conditions that most effectively promote development of primary effector populations in vivo correspond to those that are best for the generation of memory. Because of the close correspondence in frequency, it is most likely that memory CD4 cells develop directly from effector cells rather than exclusively from a separate population of precursors, as suggested in recent studies of CD8 cells (55). However, unlike CD4 cells, CD8 cells expand enormously after viral infection and then decline dramatically as the response contracts (2, 56, 57), suggesting that expansion and survival of CD4 and CD8 cells are regulated differently.
Our results showing that memory CD4 frequencies are determined during the primary response to Ag add to an increasing number of characteristics of T cell memory that are forged as primary effectors develop. Recent studies indicate that Ag-driven selection of CD4 cells with high-affinity TCRs that comprise the persistent memory population is completed within the initial few days of the primary response (20). Likewise, strongly polarizing conditions to generate Th1 or Th2 primary effector CD4 cells by 3 or 4 days in culture result in similarly polarized CD4 memory cells after adoptive transfer (58). These findings underscore the critical importance of designing vaccines to induce optimal priming of appropriate CD4 effector cells in response to initial immunization with Ag. Our data suggest that Ag targeted exclusively to DC as a vaccine strategy may not induce the optimal development of CD4 memory. Protocols that promote priming of B cells to provide costimulation for responding primary CD4 cells will achieve a much higher overall level of memory in the CD4 population. We conclude from our study that in vivo B cells provide a significant contribution to CD4 memory by promoting the generation of high frequencies of Ag-specific cells, a hallmark of immunological memory.
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Footnotes |
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2 This is manuscript number 12658-IMM from The Scripps Research Institute.
3 Address correspondence and reprint requests to Dr. Linda M. Bradley, Department of Immunology, The Scripps Research Institute, IMM-23; 10550 North Torrey Pines Road, La Jolla, CA 92037.
4 Abbreviations used in this paper: DC; dendritic cells; BCR, B cell receptor; KLH, keyhole limpet hemocyanin; LDA, limiting dilution analysis; NP, 4-hydroxy-3-nitrophenyl acetyl.
Received for publication October 18, 1999. Accepted for publication August 23, 2000.
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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D. P. Harris, S. Goodrich, K. Mohrs, M. Mohrs, and F. E. Lund Cutting Edge: The Development of IL-4-Producing B Cells (B Effector 2 Cells) Is Controlled by IL-4, IL-4 Receptor {alpha}, and Th2 Cells J. Immunol., December 1, 2005; 175(11): 7103 - 7107. [Abstract] [Full Text] [PDF]
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 S. M. McLachlan, Y. Nagayama, and B. Rapoport Insight into Graves' Hyperthyroidism from Animal Models Endocr. Rev., October 1, 2005; 26(6): 800 - 832. [Abstract] [Full Text] [PDF]
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P. M. Arnaboldi, M. J. Behr, and D. W. Metzger Mucosal B Cell Deficiency in IgA-/- Mice Abrogates the Development of Allergic Lung Inflammation J. Immunol., July 15, 2005; 175(2): 1276 - 1285. [Abstract] [Full Text] [PDF]
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S. K. O'Neill, M. J. Shlomchik, T. T. Glant, Y. Cao, P. D. Doodes, and A. Finnegan Antigen-Specific B Cells Are Required as APCs and Autoantibody-Producing Cells for Induction of Severe Autoimmune Arthritis J. Immunol., March 15, 2005; 174(6): 3781 - 3788. [Abstract] [Full Text] [PDF]
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S. Hussain and T. L. Delovitch Dysregulated B7-1 and B7-2 Expression on Nonobese Diabetic Mouse B Cells Is Associated with Increased T Cell Costimulation and the Development of Insulitis J. Immunol., January 15, 2005; 174(2): 680 - 687. [Abstract] [Full Text] [PDF]
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R. J. Messer, U. Dittmer, K. E. Peterson, and K. J. Hasenkrug Essential role for virus-neutralizing antibodies in sterilizing immunity against Friend retrovirus infection PNAS, August 17, 2004; 101(33): 12260 - 12265. [Abstract] [Full Text] [PDF]
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 S. Ugrinovic, N. Menager, N. Goh, and P. Mastroeni Characterization and Development of T-Cell Immune Responses in B-Cell-Deficient (Igh-6-/-) Mice with Salmonella enterica Serovar TyphimuriumInfection Infect. Immun., December 1, 2003; 71(12): 6808 - 6819. [Abstract] [Full Text] [PDF]
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M. P. Lemos, L. Fan, D. Lo, and T. M. Laufer CD8{alpha}+ and CD11b+ Dendritic Cell-Restricted MHC Class II Controls Th1 CD4+ T Cell Immunity J. Immunol., November 15, 2003; 171(10): 5077 - 5084. [Abstract] [Full Text] [PDF]
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S. A. Brown, J. Stambas, X. Zhan, K. S. Slobod, C. Coleclough, A. Zirkel, S. Surman, S. W. White, P. C. Doherty, and J. L. Hurwitz Clustering of Th Cell Epitopes on Exposed Regions of HIV Envelope Despite Defects in Antibody Activity J. Immunol., October 15, 2003; 171(8): 4140 - 4148. [Abstract] [Full Text] [PDF]
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B. Johansson-Lindbom, S. Ingvarsson, and C. A. K. Borrebaeck Germinal Centers Regulate Human Th2 Development J. Immunol., August 15, 2003; 171(4): 1657 - 1666. [Abstract] [Full Text] [PDF]
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A. Boitelle, H. E. Scales, C. Di Lorenzo, E. Devaney, M. W. Kennedy, P. Garside, and C. E. Lawrence Investigating the Impact of Helminth Products on Immune Responsiveness Using a TCR Transgenic Adoptive Transfer System J. Immunol., July 1, 2003; 171(1): 447 - 454. [Abstract] [Full Text] [PDF]
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P.-J. Linton, B. Bautista, E. Biederman, E. S. Bradley, J. Harbertson, R. M. Kondrack, R. C. Padrick, and L. M. Bradley Costimulation via OX40L Expressed by B Cells Is Sufficient to Determine the Extent of Primary CD4 Cell Expansion and Th2 Cytokine Secretion In Vivo J. Exp. Med., April 7, 2003; 197(7): 875 - 883. [Abstract] [Full Text] [PDF]
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H. Shen, J. K. Whitmire, X. Fan, D. J. Shedlock, S. M. Kaech, and R. Ahmed A Specific Role for B Cells in the Generation of CD8 T Cell Memory by Recombinant Listeria monocytogenes J. Immunol., February 1, 2003; 170(3): 1443 - 1451. [Abstract] [Full Text] [PDF]
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S. Fillatreau and D. Gray T Cell Accumulation in B Cell Follicles Is Regulated by Dendritic Cells and Is Independent of B Cell Activation J. Exp. Med., January 20, 2003; 197(2): 195 - 206. [Abstract] [Full Text] [PDF]
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T. Yamanaka, L. Helgeland, I. N. Farstad, H. Fukushima, T. Midtvedt, and P. Brandtzaeg Microbial Colonization Drives Lymphocyte Accumulation and Differentiation in the Follicle-Associated Epithelium of Peyer's Patches J. Immunol., January 15, 2003; 170(2): 816 - 822. [Abstract] [Full Text] [PDF]
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A. F. Cunningham, P. G. Fallon, M. Khan, S. Vacheron, H. Acha-Orbea, I. C. M. MacLennan, A. N. McKenzie, and K.-M. Toellner Th2 Activities Induced During Virgin T Cell Priming in the Absence of IL-4, IL-13, and B Cells J. Immunol., September 15, 2002; 169(6): 2900 - 2906. [Abstract] [Full Text] [PDF]
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R. P. Morrison and H. D. Caldwell Immunity to Murine Chlamydial Genital Infection Infect. Immun., June 1, 2002; 70(6): 2741 - 2751. [Full Text] [PDF]
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 D. C. Tsitoura, V. P. Yeung, R. H. DeKruyff, and D. T. Umetsu Critical role of B cells in the development of T cell tolerance to aeroallergens Int. Immunol., June 1, 2002; 14(6): 659 - 667. [Abstract] [Full Text] [PDF]
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J. Harbertson, E. Biederman, K. E. Bennett, R. M. Kondrack, and L. M. Bradley Withdrawal of Stimulation May Initiate the Transition of Effector to Memory CD4 Cells J. Immunol., February 1, 2002; 168(3): 1095 - 1102. [Abstract] [Full Text] [PDF]
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C. Ramakrishna, S. A. Stohlman, R. D. Atkinson, M. J. Shlomchik, and C. C. Bergmann Mechanisms of Central Nervous System Viral Persistence: the Critical Role of Antibody and B Cells J. Immunol., February 1, 2002; 168(3): 1204 - 1211. [Abstract] [Full Text] [PDF]
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 M. M. McNeal, J. L. VanCott, A. H. C. Choi, M. Basu, J. A. Flint, S. C. Stone, J. D. Clements, and R. L. Ward CD4 T Cells Are the Only Lymphocytes Needed To Protect Mice against Rotavirus Shedding after Intranasal Immunization with a Chimeric VP6 Protein and the Adjuvant LT(R192G) J. Virol., January 15, 2002; 76(2): 560 - 568. [Abstract] [Full Text] [PDF]
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A. Rivera, C.-C. Chen, N. Ron, J. P. Dougherty, and Y. Ron Role of B cells as antigen-presenting cells in vivo revisited: antigen-specific B cells are essential for T cell expansion in lymph nodes and for systemic T cell responses to low antigen concentrations Int. Immunol., December 1, 2001; 13(12): 1583 - 1593. [Abstract] [Full Text] [PDF]
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N. M. Milicevic, B. Luettig, C. Trautwein, T. Wustefeld, M. Mahler, P. Jecker, K. Wonigeit, and J. Westermann Splenectomy of rats selectively reduces lymphocyte function-associated antigen 1 and intercellular adhesion molecule 1 expression on B-cell subsets in blood and lymph nodes Blood, November 15, 2001; 98(10): 3035 - 3041. [Abstract] [Full Text] [PDF]
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C. C. Bergmann, C. Ramakrishna, M. Kornacki, and S. A. Stohlman Impaired T Cell Immunity in B Cell-Deficient Mice Following Viral Central Nervous System Infection J. Immunol., August 1, 2001; 167(3): 1575 - 1583. [Abstract] [Full Text] [PDF]
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 I. M. Orme The search for new vaccines against tuberculosis J. Leukoc. Biol., July 1, 2001; 70(1): 1 - 10. [Abstract] [Full Text] [PDF]
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) along with the average frequency at each time point (
), which
is expressed in the table below as a fraction.
37% of the wells tested
were negative for IL-2 in culture supernatants where the plating
efficiency is one cell plated per well. At that dilution where
IL-2-responsive CD4 cells per well are limiting, the amount of IL-2 per
cell is shown for each of the 36 replicate cultures that scored
positive. Shown are results from a representative experiment with only
the positive wells from two individual µMT and C57BL/6 mice
displayed. A well was scored positive if the amount of IL-2 (pg) per
cell was >3 SDs above the mean pg per cell determined from cultures
containing KLH-pulsed APC alone (dashed line). The mean value (i.e.,
average amount of IL-2 secreted per responsive cell) is shown
(
).
