| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
* Center of Anatomy, Medical School of Hannover, Hannover, Germany;
Division of Gastroenterology, University of Rostock, Rostock, Germany; and
Institute of Anatomy, Medical University of Luebeck, Luebeck, Germany
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
We recently stimulated rat T cells from mLN in vitro polyclonally via
the TCR and CD28 and transferred these cells (RT.7B) i.v. into congenic
rats (RT.7A), allowing the tracing of injected cells in vivo and
avoiding the potentially harmful effect of in vitro labeling. In
addition, the proliferative capacity of the injected effector T cells
was analyzed in various organs by measuring bromodeoxyuridine
(BrdU) incorporation. These studies showed that effector mLN T cells
entered mLN, PP, and the small intestine at a similar rate. However,
within these three sites, effector mLN T cells proliferated at a higher
rate than those that had entered peripheral lymph nodes (pLN)
(4, 5, 6), leading to the preferential accumulation of
effector mLN T cells in mLN, PP, and lamina propria of the gut
(4). Further in vitro studies showed that the cytokines
TGF
-1 and IL-4 are involved in the maintenance of the proliferative
capacity among the effector mLN T cells (6). Since
TGF-1 and IL-4 are preferentially expressed in mLN, PP, and gut
(6), it is very likely that these cytokines are also
involved in vivo in mediating the preferential proliferation of
effector mLN T cells, resulting in their site-specific accumulation
(7).
However, many factors regulating the preferential proliferation of effector T cells are still unclear. Therefore, in the present study we analyzed where the capacity of preferential proliferation is imprinted on effector mLN T cells and up to which developmental stage of T cell life it lasts. Furthermore, dendritic cells (DC) in the T cell area of lymphoid organs activate naive T cells (8) and it was investigated whether they might be involved in the regulation of effector T cell proliferation. Finally, we studied whether and how CD4+ and CD8+ effector mLN T cells are different in their proliferative and migratory capacity. Such information is important to modify the distribution of effector T cells in vivo to therapeutically influence the course of many diseases (1, 9).
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Rats from the standard inbred strain LEW/Ztm (RT.7a) and the congenic strain LEW.7B/Won (RT.7b) were bred and maintained at the central animal laboratory of the Medical School of Hannover (Hannover, Germany). The LEW.7B strain is identical to the congenic strain originally designated LEW.Ly1.2 (10). The RT system is a diallelic polymorphism of the CD45 molecular system (11).
Proliferation among the injected mLN and pLN T cells in vivo
Cell suspensions were prepared from LEW.7B mLN and pLN and
stimulated via the 
TCR and CD28 as previously described
(4). To generate rested effector mLN T cells, effector mLN
T cells were cultured for another 4 days in medium containing IL-2
(1/100 dilution, supernatant of cultured IL-2-transfected Chinese
hamster ovary cells). Then 100–200 x
106 effector mLN and pLN T cells (LEW.7B) and
rested effector mLN T cells were characterized by flow cytometry as
described previously (4, 5) and injected i.v. into LEW
rats over 2 min. They were sacrificed 1–3 days after injection. One
hour before exsanguination, the recipients received 5 mg BrdU/100 g
body weight i.v. (12). Injected cells were detected by the
mAb His41 against the LEW.7B phenotype via flow cytometry
(11). The percentage of BrdU+ cells
among His41+CD4+ and
His41+CD8+ T cells was
analyzed by FACScan as described below. At least 5 x
104 viable injected cells were analyzed.
Stimulation of T cells and injection of these cells in vivo
About 2–2.5 x 108 LEW.7B mLN cells
were stimulated via the TCR (Ab R73) and CD28 (Ab JJ319) and
cultured in the presence of 10 µM BrdU for 3 days as previously
described (4). After expansion of stimulated cells,
2–2.5 x 108 stimulated
BrdU+ mLN T cells were injected i.v. into LEW
rats. At 1–4 days after injection, the recipients were exsanguinated,
the blood, mLN, and axillary LN/cervical LN (pLN) were removed, and
cell suspensions were prepared. After washing, the injected T
lymphocytes were detected by the mAb His41 against the LEW.7B phenotype
(11) and their BrdU content was identified via flow
cytometry (6). At least 5 x
104 viable injected cells were analyzed.
Quantification of cytokine mRNA in effector mLN and pLN T cells
Cell suspensions from mLN and pLN were prepared and cells were
stimulated via mAbs against the TCR and CD28. At 3 days after
stimulation, cDNAs were synthesized from these effector mLN and pLN T
lymphocytes as described elsewhere (6) and competitive PCR
was performed using a synthetic DNA control fragment (CF) as an
internal standard (13). The 613-bp CF contained
rat-specific primers for multiple cytokines (TGF-1, IFN-
, IL-2,
IL-4, and IL-10 and for the housekeeping protein -actin
(6). The PCR products were separated
electrophoretically and the intensity of the ethidium bromide
fluorescence was measured with an electronic camera (6).
The quantitative evaluation was based on the amplification of 10-fold
dilutions of CF (1 pg to 0.01 fg) followed by measuring the
fluorescence intensity of the respective amplicons. The proportions of
the PCR products coamplified from sample cDNA and a defined CF
concentration were analyzed, resulting in relative concentrations of
cDNA with respect to the CF concentration.
Detection of contact between effector T cells and DC
Injected effector T cells and DC in the mLN and pLN were detected via immunohistology (14). Briefly, effector mLN T cells were injected into congenic recipients. Three days after injection, the animals received BrdU i.v. One hour after BrdU administration, the mLN were removed. Cryostat sections were made. Injected T cells were identified with the mAbs His41 (11) and DC were detected via an anti-ICAM-1 Ab (1A29, IgG1; Serotec, Oxford, U.K.) and their morphology and localization in the paracortex determined via an immunohistological three-color staining and visualization with the peroxidase-anti-peroxidase/alkaline phosphatase-anti-alkaline phosphatase technique (4, 15). About 500-1000 His41+ T cells were counted microscopically and their contact with DC was calculated as a percentage. By revealing the BrdU incorporation among the injected His41+ T cells, which had contact with DC in the mLN, the percentage of proliferation among the injected effector mLN T cells in response to the contact with DC was demonstrated.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
).
|
To investigate whether the property of preferential proliferation
is retained beyond the effector phase, effector mLN T cells were
generated in vitro as described and were then rested in the presence of
only IL-2 for another 4 days. In contrast to freshly generated effector
T cells which are large proliferating cells, rested effector mLN T
cells are small and the percentage of proliferating cells is <1%,
comparable to the proliferation rate among naive T cells (Table I). Interestingly, in contrast to naive T
cells, rested effector T cells still express high levels of activation
markers such as IL-2R, ICAM-1, 4 integrin, and
MHC class II (Table I). Furthermore, most of them are CD45RC negative
(Table I), indicating that after resting the surviving T cells acquire
a memory phenotype (16). These cells were then injected
into congenic recipients, and 3 days after injection the recipients
received BrdU i.v. Since mLN and pLN were removed 1 h later, it
was guaranteed that the cells present in the lymph nodes during that
time incorporated BrdU. The injected T cells were identified and the
percentage of BrdU+ cells among the injected T
cells was determined by flow cytometry. Interestingly, comparable to
effector mLN T cells, the injected T cells that had rested for 4 days
also showed an increased proliferation rate in mLN compared with that
in pLN, although on a lower level than that of effector mLN T cells
(Fig. 1
). Surprisingly, when effector mLN T cells were injected and
analyzed for their proliferation 56 days after injection, the same
increased proliferative capacity was observed in the mLN. The level was
comparable to rested effector T cells (Fig. 1). Since naive mLN T cells
had a comparable proliferation rate after entry into mLN and pLN
(6), the present data indicate that the property of
preferential proliferation is acquired during activation and then
maintained on a lower level for a long time after the effector stage
(>56 days after stimulation).
|
). The data show that
preferential proliferation is only linked to mLN T cells. Although BrdU
incorporation and activation marker expression (IL-2R, ICAM-1, MHC
class II) were comparable between effector mLN and pLN T cells before
injection (4), analysis of cytokine mRNA expression among
them showed that the two populations considerably differed in the
expression of IL-2, IFN-, IL-10, and TGF-1 mRNA (Fig. 2), showing that effector mLN and pLN T
cells have different cytokine profiles probably determining their
function and their proliferative capacity in vivo.
|
DC are known to interact with naive, effector, and memory T cells, thereby regulating the quality of immune responses (17). To investigate whether DC are also involved in the regulation of the proliferative capacity among effector mLN T cells within mLN, effector mLN T cells were injected into congenic recipients. Three days later, the recipients received BrdU and 1 h later the mLN were removed. Cryostat sections were prepared, and DC, injected effector mLN, and incorporated BrdU were identified by three-color immunohistochemistry.
Since ICAM-1 and MHC class II are highly expressed on DC, these two
molecules were used to detect the DC. Both molecules are also expressed
by B cells and macrophages in the secondary lymphoid organs. However,
their expression of ICAM-1 is lower than on DC (Fig. 3A). Therefore, DC were
detected by ICAM-1 staining in the paracortex, which nicely shows the
specific morphology of the DC. In addition, to rule out that
macrophages or B cells were detected in the paracortex, B cells
(anti-IgD) and macrophages (ED-1; Serotec) were stained and their
morphology was compared with ICAM-1+ DC (Fig. 3A).
|
B). By analyzing the
proliferation rate in these two groups, it became clear that contact
with DC enhanced proliferation of injected effector mLN T cells (Fig. 3C). Different proliferation kinetics for CD4+ and CD8+ effector mLN T cells in mLN and pLN
To analyze the proliferative capacity of
CD4+ and CD8+ cells among
effector mLN T cells after migration into mLN and pLN, effector mLN T
cells (LEW.7B) were generated as described and injected into congenic
recipients (LEW.7A). At various time points after injection, the
animals received BrdU and 1 h later the injected T cells were
identified by flow cytometry, and the percentage of
BrdU+ cells among the injected
CD4+ and CD8+ T cells was
determined. After in vitro generation and directly before injection,
the CD8+ effector T cells showed a significantly
higher proliferation rate compared with that of
CD4+ effector T cells (Fig. 4). However, in mLN from 2 days after
injection onward, CD4+ effector T cells
proliferated to a higher degree than CD8+
effector T cells. Over 2 days the proliferation rate of both
populations increased 2- to 3-fold in mLN, maintaining, however, a
proliferative preference for CD4+ over
CD8+ effector T cells. In pLN, the proliferation
of CD4+ effector mLN T cells was comparable to
that of CD8+ effector T cells 2–3 days after
injection (Fig. 4) and did not change over time. Thus, in contrast to
pLN, the mLN microenvironment favors proliferation of injected effector
mLN T cells, especially 3 days after injection, and among the effector
mLN T cells CD4+ T cells proliferated two times
more than CD8+ T cells.
|
Then it was investigated how the different proliferation
properties of CD4+ and CD8+
effector mLN T cells affected their localization in mLN and pLN over
time. Effector mLN T cells were generated as described. Since it is
known that not all lymphocytes respond to such procedures
(18), BrdU was given during the culture, which made it
possible to follow in vivo only those cells which had been in the S
phase at least once during in vitro activation. Then, we injected the
BrdU+-labeled effector mLN T cells into the
congenic rats and their distribution was analyzed in mLN, pLN, and
blood. Although the percentages of CD4+ and
CD8+ cells were comparable among the injected
effector mLN T cells, CD4+ effector mLN T cells
accumulated in the mLN over time (Fig. 5A), correlating well with
their proliferation pattern. In addition, the percentage of apoptotic
cells among the CD4+ effector T cells was
decreased compared with the CD8+ T cells 2–3
days after injection (percentage of apoptotic cells among
CD4+: 11 ± 2.0%;
CD8+: 16 ± 3.5%; mean and SEM,
n = 4). Surprisingly, however,
CD8+ effector mLN T cells preferentially
accumulated in pLN (Fig. 5B), although their apoptosis in
pLN was comparable to that in the mLN (percentage of apoptosis among
CD8+: 17 ± 2.5%; mean and SEM,
n = 4) and their proliferation was not different from
that of CD4+ cells (Fig. 4). This indicates that
the accumulation of CD4+ effector T cells in mLN
might be due to three mechanisms: 1) preferential proliferation of
CD4+ effector mLN T cells in mLN (Fig. 4), 2)
decreased apoptosis of CD4+ effector mLN T cells
in mLN, and 3) preferential emigration of CD8+
effector mLN T cells from mLN. Indeed, 1 day after injection
CD8+ effector mLN T cells were preferentially
found in the spleen (CD8+, 56 ± 4.1%;
CD4+, 44 ± 3.2%; n =
9–10) and from 2 days after injection onward in the blood (Fig. 5C), indicating that the higher number of
CD8+ effector mLN T cells in pLN is due to their
higher availability in the blood and their subsequent migration into
the spleen and pLN. Surprisingly, when adhesion molecule expression was
measured among the CD4+ and
CD8+ effector mLN T cells before injection and
also 3 days after injection in the mLN, IL-2R, ICAM-1,
4 integrin, MHC class II, LFA-1, CD2, and
L-selectin were not different among CD4+ and
CD8+ effector mLN T cells (Table II). This indicates that these molecules
play a minor role in the different distribution of
CD4+ and CD8+ effector mLN
T cells in vivo.
|
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The microenvironment experienced during activation determines the fate of effector T cells in vivo
The present study shows that the increased proliferation of
effector mLN T cells after migration into mLN is also observed for
effector mLN T cells, which were observed 56 days after injection, but
not for naive mLN T cells (6). This indicates that the
property to react with increased proliferation after migration is
acquired during activation and is maintained, although on a lower
level, even after returning to a resting stage. Since this was also
observed 56 days after injection, it is likely that this property is
imprinted on effector mLN T cells for a long time. However, it is not
known at the moment whether it is lifelong or only for a certain period
of time. Thus, effector mLN T cells and their progeny accumulate in
regions where reinfection is likely and they are urgently needed.
Interestingly, although both effector mLN and pLN T cells accumulate
after migration throughout the body in their tissue of activation
(4), only effector mLN T cells showed increased
proliferation in mLN, whereas effector pLN T cells had a comparable
proliferation rate in mLN and pLN (Fig. 1). Recent data indicate that
effector pLN T cells preferentially survive after migration into pLN,
but undergo increased apoptosis in other tissues (e.g., mLN). This also
results in preferential accumulation (4, 20) and shows
that in vivo different mechanisms are responsible for the same
observation.
It is known that in mLN, TH2 cytokines prevail whereas in pLN TH1
cytokines dominate (6, 21), and recent data indicate that
the different cytokine milieu present during activation is responsible
for the proliferation properties of effector mLN and pLN T cells after
entry into mLN and pLN, respectively (6). The present
study clearly demonstrates that despite a comparable activation status
and proliferative capacity after stimulation (4), effector
T cells from mLN and pLN produce different cytokines (Fig. 2), and
further studies have to clarify whether the expression of
cytokine receptors also differs between the two effector T cell
populations. If a TH2 cytokine receptor pattern dominated among
effector mLN T cells, this could explain their increased proliferation
rate in mLN.
DC influence the cytokine milieu in mLN
The present study shows that effector mLN T cells in contact with
DC proliferate approximately two times more than those cells that have
no contact. Furthermore, it is known that IL-4 and TGF-1 mediate
preferential proliferation of effector mLN T cells in vitro
(6). Together this suggests that DC themselves produce
these cytokines. Effector mLN T cells in contact with DC or in the
immediate vicinity of DC would experience high levels of cytokines,
resulting in higher proliferation rates, whereas effector mLN T cells
further away would experience lower levels, resulting in a lower
proliferation rate. However, this scenario does not exclude other
sources of cytokines such as other lymphocytes, fibrocytes, and
components of the extracellular matrix. DC, which are strategically
located in the T cell area of lymphoid tissues (22),
determine during activation of naive T cells the subsequent cytokine
requirement of the resulting effector T cells, thereby strongly
influencing their in vivo distribution. The cytokine pattern imprinted
on the generated effector T cells seems to vary between mLN and pLN,
and it is very likely that, in contrast to the polyclonal stimulation
in vitro used in the present study, during Ag-triggered stimulation in
vivo, the imprinted cytokine requirement is more specific, resulting in
an even more focused accumulation of effector T cells at sites where
they are needed. Since DC also seem to be relevant in providing naive T
cells with either MHC class I or II molecules which they need for
survival (7, 23), this clearly underlines the important
role of DC both in maintaining the homeostasis of naive T cells and in
generating effector T cells with characteristic accumulation properties
during an immune response.
CD4+ and CD8+ effector mLN T cells differ in their proliferation and migration characteristics
Although both CD4+ and
CD8+ effector T cells show a higher proliferation
rate after migration into mLN compared with that after entry into pLN
(Fig. 4), the present study reveals major differences between the two
subsets. After in vitro generation and before injection, the percentage
of proliferating cells was about 2-fold higher among
CD8+ effector mLN T cells than among
CD4+ cells. However, this ratio reversed after
entry into mLN beyond 2 days after injection in which
CD4+ effector mLN T cells had a proliferation
rate two times higher than the injected CD8+ T
cells. This indicates that factors regulating effector mLN T cell
proliferation are different for CD4+ and
CD8+ cells, and that in vivo the microenvironment
of mLN preferentially supports the former. The differential regulation
of proliferation is characteristic for mLN since in pLN the two subsets
proliferate at a comparable rate beyond 2 days after injection. The
factors responsible for the differential proliferation of
CD4+ and CD8+ effector T
cells in mLN are completely unknown.
In line with the increased proliferation rate of
CD4+ effector T cells is their decreased
apoptosis early after injection. Both the increased proliferation and
the decreased apoptosis result in their increased survival and
therefore in their increased accumulation in mLN over time (Fig. 5).
Surprisingly, however, CD8+ effector mLN T cells
accumulated in pLN, although here both CD4+ and
CD8+ effector mLN T cells proliferate at a
comparable rate and apoptosis of CD8+ effector
mLN T cells was not different from those CD8+
effector mLN T cells in the mLN. This shows that to identify the cause
of lymphocyte accumulation in vivo, not only proliferation within a
tissue but also entry, cell death, and exit have to be considered
(7, 24). At present, we have no evidence that
CD4+ and CD8+ effector mLN
T cells differ regarding entry into the lymph nodes. This is underlined
by the finding that CD4+ and
CD8+ effector mLN T cells had comparable
expression of adhesion molecules directly before injection and after
migration in vivo. However, there seems to be a difference in exit from
the tissue. From 2 days after injection onward,
CD8+ effector T cells prevail in the blood.
Therefore, more CD8+ than
CD4+ effector mLN T cells are available for
entering pLN, thus providing a likely explanation for the preferential
accumulation of CD8+ effector mLN T cells in pLN,
although no difference in the proliferation rate was seen between the
two subsets within pLN. This conclusion is supported by the comparable
kinetic pattern of CD4+ and
CD8+ effector mLN T cells in blood and pLN (Fig. 5). It suggests that, beside the preferential exit of effector
CD8+ effector T cells from mLN, it is mainly the
availability in the blood which determines the number of effector mLN T
cells in pLN. Evidence was obtained recently that among the progeny of
the effector mLN T cells dividing within mLN, preferentially the
progeny of the CD8+ effector mLN T cells are able
to leave the lymph node into the blood (5). Similar
observations were made in HIV-infected primates in which activated
CD4+ T cells seem to be more sessile, whereas
activated CD8+ T cells are able to leave into the
blood and migrate through the body (Ref. 25 and S.
Sopper, personal communication). However, the different migratory
properties of CD4+ and CD8+
effector mLN T cells have to be confirmed by injecting them i.v. and by
monitoring their appearance in the thoracic duct after transmigration
of the mLN (7).
Thus, effector mLN T cells after entering mLN develop a proliferation rate that is significantly higher than that in pLN. CD4+ effector mLN T cells preferentially survive and remain in the mLN as has been also shown for effector/memory CD4+ T cells in the mouse model (22, 26) and correlates with their function to regulate the nature of the immune response within the tissue. In contrast, CD8+ effector mLN T cells are able to leave the mLN in considerable numbers, thereby supporting their function to screen the tissues of the body for infected cells.
Conclusion
Many diseases are characterized by the accumulation of effector T cells in the affected tissue. For example, in inflammatory bowel disease accumulations of effector CD4+ T cells are found in the lamina propria of the diseased part of the intestine (1). Our study indicates that by altering the cytokine milieu in the affected tissue, the survival of the harmful effector CD4+ T cells might be modulated in a beneficial way. In addition, by modifying the exit of autoreactive CD8+ effector T cells from the lymph node unwanted immune reactions, such as destruction of the pancreatic islets, might be preventable (27).
|
Acknowledgments |
|---|
|
Footnotes |
|---|
2 Address correspondence and reprint requests to Dr. Ulrike Bode, Anatomie II, OE 4120, Medizinische Hochschule Hannover, Carl-Neuberg-Strasse 1, D-30625 Hannover, Germany. E-mail address: Bode.Ulrike{at}MH-Hannover.de
3 Abbreviations used in this paper: mLN, mesenteric lymph node; pLN, peripheral LN; DC, dendritic cell; PP, Peyer’s patches; BrdU, bromodeoxyuridine; CF, control fragment.
Received for publication April 18, 2002. Accepted for publication September 18, 2002.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
-1 and IL-4 maintained proliferation. Eur. J. Immunol. 31:2116.[Medline]
This article has been cited by other articles:
|
|
 |
|
  M. Ahrendt, S. I. Hammerschmidt, O. Pabst, R. Pabst, and U. Bode Stromal Cells Confer Lymph Node-Specific Properties by Shaping a Unique Microenvironment Influencing Local Immune Responses J. Immunol., August 1, 2008; 181(3): 1898 - 1907. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Kalies, P. Konig, Y.-M. Zhang, M. Deierling, J. Barthelmann, C. Stamm, and J. Westermann Nonoverlapping Expression of IL10, IL12p40, and IFN{gamma} mRNA in the Marginal Zone and T Cell Zone of the Spleen after Antigenic Stimulation J. Immunol., April 15, 2008; 180(8): 5457 - 5465. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 U. Bode, M. Lorchner, R. Pabst, K. Wonigeit, S. Overbeck, L. Rink, and J. Hundrieser The superantigen-induced polarization of T cells in rat peripheral lymph nodes is influenced by genetic polymorphisms in the IL-4 and IL-6 gene clusters Int. Immunol., January 1, 2007; 19(1): 81 - 92. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Kalies, M. Blessenohl, J. Nietsch, and J. Westermann T Cell Zones of Lymphoid Organs Constitutively Express Th1 Cytokine mRNA: Specific Changes during the Early Phase of an Immune Response J. Immunol., January 15, 2006; 176(2): 741 - 749. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Schif-Zuck, J. Westermann, N. Netzer, Y. Zohar, M. Meiron, G. Wildbaum, and N. Karin Targeted Overexpression of IL-18 Binding Protein at the Central Nervous System Overrides Flexibility in Functional Polarization of Antigen-Specific Th2 Cells J. Immunol., April 1, 2005; 174(7): 4307 - 4315. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Westermann, U. Bode, A. Sahle, U. Speck, N. Karin, E. B. Bell, K. Kalies, and A. Gebert Naive, Effector, and Memory T Lymphocytes Efficiently Scan Dendritic Cells In Vivo: Contact Frequency in T Cell Zones of Secondary Lymphoid Organs Does Not Depend on LFA-1 Expression and Facilitates Survival of Effector T Cells J. Immunol., March 1, 2005; 174(5): 2517 - 2524. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
, pLN; •, mLN).
) and CD8+ T cells (
) among the mLN
BrdU+ T cells (y-axis) are given (two to six
independent experiments). *, Significant differences between
CD4+ and CD8+ cells among BrdU+ mLN
T cells in Student’s t test, p <
0.05