| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
*
Department of Molecular Cell Biology, Laboratory of Experimental Laboratory Medicine and
Department of Pathophysiology, Laboratory of Experimental Immunology, Faculty of Medicine, Catholic University Leuven, Leuven, Belgium; and
Macrozyme B.V., Amsterdam, The Netherlands
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Although pneumococcal cell wall polysaccharides are highly immunogenic, Abs to cell wall polysaccharides are not protective against invasive pneumococcal infection (3, 4, 5). Protection against S. pneumoniae is mainly provided by Abs to pneumococcal capsular polysaccharides (caps-PS)3 (6). Therefore, it has become of extreme importance to understand the mechanism by which protection to caps-PS is provided by the immune system.
The Ab response to pneumococcal polysaccharides is considered thymus independent (TI) because neonatally thymectomized mice and athymic nude mice are able to mount an Ab response similar in magnitude to that of conventional thymus-bearing mice (7, 8, 9). Because T lymphocytes or T lymphocyte products increase the Ab response to pneumococcal polysaccharides, pneumococcal caps-PS are classified as TI type 2 (TI-2) Ags (10). Whereas TI-2 Ags do not need T lymphocytes to induce an Ab response, thymus-dependent (TD) Ags (e.g., proteins) require participation of CD4+ T lymphocytes to generate an immune response (11). The immune response to TD Ags critically depends on the interaction between CD40 ligand (CD40L), a molecule which is transiently expressed on the surface of activated CD4+ T lymphocytes, and CD40 expressed on the surface of B lymphocytes (12). This interaction activates the resting B lymphocyte to produce Abs to TD Ags and is important for germinal center creation, memory B lymphocyte formation, and Ig class switching (13, 14, 15, 16, 17).
The question whether the CD40-CD40L interaction plays a role in the immune response to TI-2 Ags in general and pneumococcal polysaccharides in particular remains unsolved. There are contradictory data with regard to the role of CD40L in the immune response to TI-2 Ags after immunization with an intact extracellular microorganism or with a polysaccharide-protein conjugate. Wu et al. (18), using CD40L knockout mice, reported that the IgG response against phosphorylcholine (a TI-2 Ag) in mice immunized with a nonencapsulated variant of S. pneumoniae is T lymphocyte and CD40L dependent. However, it has also been described that a blocking anti-CD40L Ab (MR1) had little or only modest effect on the antiphosphorylcholine response and that CD40-/- dendritic cells elicited an anti-phosphorylcholine response that was comparable to that observed for wild-type dendritic cells (19). Szomolanyi-Tsuda et al. (20) stressed the role of the CD40-CD154 interaction in anti-polyoma virus thymus cell-independent IgG responses. Finally, it has been described 1) that neutralization of CD40L reduced the Ab response to pneumococcal caps-PS elicited by immunization with whole bacteria or with a caps-PS-protein conjugate and 2) that the immune response to a caps-PS-protein conjugate was higher in wild-type mice than in CD40L-deficient mice (21, 22). In contrast to immune responses to TI Ags on intact microorganisms or in polysaccharide-protein conjugates, immune responses to soluble polysaccharides are believed to be T lymphocyte and CD40L independent. Blocking the CD40-CD40L interaction with an anti-CD40L mAb did not inhibit the Ab formation against trinitrophenyl-conjugated Ficoll, a TI-2 Ag and CD40 and CD40L knockout mice mounted a normal Ab response to haptenated Ficoll (22, 23, 24, 25). Recently, it was demonstrated that blocking CD40L in mice did not affect the Ab response against isolated pneumococcal caps-PS type 6B (21). However, there is indirect evidence that the CD40-CD40L interaction might be important for the immune response to soluble TI-2 Ags, since it was demonstrated that in vivo administration of trinitrophenyl-conjugated Ficoll induced a rapid expression of CD40L on CD4+ T lymphocytes (15). Furthermore, Abs that stimulate the CD40 molecule in mice augment the Ab response to purified pneumococcal caps-PS (26). It has been suggested that this stimulatory effect of this agonist anti-CD40 on the anti-caps-PS immune response is mainly due to increased activity of accessory cells that affect plasmablast growth and differentiation rather than mimicry of T lymphocyte help (27).
The present study was undertaken to determine the role of the CD40-CD40L interaction in the immune response to pneumococcal caps-PS Ags. We investigated whether the CD40-CD40L interaction between B cells and CD4+ and/or CD8+ T lymphocytes plays an important role in the regulation of the murine immune response to caps-PS.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Pneumovax, a 23-valent pneumococcal vaccine containing 25 µg
of the caps-PS (Danish nomenclature) types 1–5, 6B, 7F, 8, 9N, 9V,
10A, 11A, 12F, 14, 15B, 17F, 18C, 19A, 19F, 20, 22F, 23F, and 33F, was
obtained from Aventis Pasteur (Brussels, Belgium). Pneumococcal
caps-PS and C-polysaccharide were obtained from American Type Culture
Collection (Manassas, VA). MR1, a monoclonal blocking Ab to murine
CD40L, was provided by Macrozyme B.V. (Amsterdam, The Netherlands).
Polyclonal hamster IgG was obtained from Biotrend Chemikalien
(Köln, Germany). These Abs were purified using the Spectra/Por
Float-A-Lyser from Spectrum Laboratories (Rancho Dominguez, Canada).
Purified rat anti-mouse CD19 (TD3), PE anti-mouse CD4 (L3T4),
PE anti-mouse CD8a (Ly-2), FITC polyclonal anti-mouse CD3e
(CD3
chain), FITC polyclonal anti-rat Ig were purchased from BD
Biosciences (Erembodegem-Aalst, Belgium). Peroxidase-conjugated goat
anti-mouse IgM and IgG were obtained from Nordic Immunological
Laboratories (Tilburg, The Netherlands). Goat serum and PBS were
purchased from Life Technologies (Paisley, U.K.).
3,3'-5,5'-tetramethylbenzidine was purchased from DAKO (Heverlee,
Belgium). HCl (1 N) and
H2SO4 (3 N) solution were
obtained from Merck (Darmstadt, Germany). Cell Strainers, 70-µm
nylon, were supplied by BD Labware Europe (Le Pont De Claix, France).
RPMI 1640 culture medium, glutamine, Tween 20
(polyoxyethylenesorbiton), agarose type I, HEPES, anti-mouse IgM
conjugated with alkaline phosphatase, 5-bromo-4-chloro-3-indolyl
phosphate p-toluidine salt, gentamicin, 2-ME, and PWM were
obtained from Sigma-Aldrich (Bornem, Belgium).
N-(3-dimethylaminopropyl)-N'-ethylcarbiimide
hydrochloride), 5 g dissolved in 500 ml aqua destillata,
was obtained from Merck. Dynabeads were purchased from Dynal Biotech
(Hamburg, Germany). Covalink ELISA plates were obtained from Nunc
(Nalge, Denmark) and flexible 96-well ELISA plates were obtained from
Titertek (Merlin Diagnostic System BV; Breda, The Netherlands).
Mice
BALB/c mice were bred at the Proefdierencentrum of the Katholieke Universiteit Leuven in Heverlee. Animals were used at the age of 6–8 wk and were kept under a standard protocol with free access to pelleted food and water. Six- to 8-wk-old scid/scid mice were provided by J. Mertens of the REGA Institute (Leuven, The Netherlands). They were kept in sterilized plastic cages and were given sterilized tap water and sterilized pelleted food. The scid/scid mice were tested for leakiness by analyzing the level of mouse IgG Abs according to a previously described ELISA (28). Only mice with IgG concentrations <2 µg/ml were used in the experiments. Both mice strains were held in a room with a 12-h/12-h light/dark cycle. Approval of the study was granted by the local committee of the Catholic University Leuven.
Immunization of BALB/c mice
BALB/c mice were immunized with Pneumovax. The vaccine was 1/25 diluted in 0.9% NaCl. Five hundred microliters of this diluted vaccine was given i.p. After 7 and 14 days, blood was drawn by intracardial puncture and anti-caps-PS Abs were detected by ELISA (see later in text). In experiments in which the effects of MR1 were studied, 500 µg of MR1 was injected i.p. 1 day before immunization with Pneumovax. Five hundred micrograms of the hamster IgG control Ab was injected i.p. into the control group.
ELISA for detection of anti-caps-PS Abs
A Covalink ELISA 96-well plate was coated overnight at 37°C with pneumococcal polysaccharide (final concentration, 3 µg/ml in N-(3-dimethylaminopropyl)-N'-ethylcarbiimide hydrochloride). After coating, the plate was washed three times with 0.05% Tween 20 in PBS. Thereafter, the plate was blocked for 1 h at 37°C with 10% goat serum in PBS. Serum was treated with pneumococcal C-polysaccharide to remove anti-C-polysaccharide Abs. Such treatment consisted of incubation of the serum with a 1/4 dilution of C-PS for 1 h at 37°C. Serial dilutions of serum were made in PBS containing 2% goat serum. Serum was added to the wells and incubated for 2 h at 37°C. After washing three times with 0.05% Tween 20 in PBS, peroxidase-conjugated goat anti-mouse IgM or goat anti-mouse IgG in a dilution of 1/5000 was added to the wells. The plate was incubated for 1.5 h at 37°C. Thereafter, 3,3'-5,5'-tetramethylbenzidine was added for color development. After 15 min, the reaction was stopped by an acid stock solution that contained 1 N HCl and 3 N H2SO4. Plates were read at 450 nm.
In vitro cell culture
Mice were sacrificed under ether anesthesia and the spleen was removed. Mouse mononuclear cells were isolated from the spleen using a Cell Strainer. The lymphocytes were cultured in Falcon tissue culture flasks in RPMI 1640 supplemented with 10% FCS, 2 mM glutamine, 15 mM HEPES, 50 µg/ml gentamicin, 5 x 10-5 M 2-ME, and 25% (v/v) T cell-replacing factor. T cell-replacing factor is defined as the supernatant of a 24-h culture of irradiated mouse T cells in the presence of PWM (29). PWM was removed by incubating 1 x 108 erythrocytes per PWM for 1 h at 37°C (30). Cells were cultured at a density of 1 x 106 per ml and were stimulated with caps-PS type 19F or caps-PS type 3. Cultures were harvested after 3–5 days of incubation at 37°C in a humidified atmosphere with 5% CO2. Ab production was measured using an ELISPOT assay (see later in text). When indicated, CD4+ and/or CD8+ cells were removed using Dynabeads, or MR1 was added.
ELISPOT assay
Cultured cells were assayed after 3–5 days for the presence of anti-caps-PS Ab-producing cells in an ELISPOT assay as previously described (31, 32). The culture system as described above allows only generation of IgM-producing cells (33, 34). Flexible 96-well ELISA plates were coated overnight with PS 19F or PS 3 in 0.9% NaCl. Thereafter, plates were blocked with 1% BSA in PBS/0.05% Tween 20. Serial dilutions of cultured cells were added to the wells and incubated for 2–4 h at 37°C with 5% CO2 and 100% relative humidity. After removal of the cells, wells were incubated with alkaline phosphatase-conjugated goat anti-mouse IgM for 2 h at 37°C. After a final wash step, spots were visualized by incubation with 5-bromo-4-chloro-3-indolyl phosphate substrate in an agarose gel. After gelling, the plates were incubated for 1 h at 37°C. Spots were counted under a dissection microscope and expressed as spots per 106 cells. Each spot represented an Ab-secreting cell.
Transferring spleen cells from BALB/c mice to SCID mice
BALB/c mice were sacrificed under ether anesthesia and the spleen was removed. Mouse mononuclear cells were isolated from the spleen (see above). When indicated, CD4+ and/or CD8+ lymphocytes were removed using Dynabeads. The percentage of B lymphocytes, CD4+ and CD8+ T lymphocytes in the lymphogate was determined by flow cytometry (FACScan; BD Biosciences). The cells were dissolved in 500 µl 0.9% NaCl and injected i.p. into SCID mice. On the same day, 500 µg of MR1 was administered and the next day, Pneumovax was given i.p. After 14 days, blood was drawn by heart puncture and IgM and IgG Abs to caps-PS were measured.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
To address the question whether CD40-CD40L interactions are
necessary for the generation of an Ab response to pneumococcal caps-PS
in vivo, the effect of anti-CD40L treatment on mice immunized with
Pneumovax was studied. Mice immunized with Pneumovax were treated with
either MR1 or with a control hamster IgG Ab (control group). MR1
administration was done 1 day before immunization with the vaccine. The
IgM as well as the IgG Ab response to various polysaccharide types was
determined 14 days after immunization. The results are shown in Figs. 1
(for IgM) and
2 (for IgG). Anti-CD40L treatment
inhibited the primary IgM Ab response to all caps-PS types tested (3,
4, 14, and 19F). As has been previously demonstrated, the magnitude of
the IgG response was dependent on the serotype (35). There
was a high immune response to caps-PS type 3, an intermediate immune
response to caps-PS type 14, and almost no IgG immune response to
caps-PS type 19F. Immunization of mice with Pneumovax resulted in
significantly variable IgG responses to caps-PS type 4. MR1
unmistakably inhibited the high anti-caps-PS type 3 immune response
and the intermediate anti-caps-PS type 14 response. MR1 did not
affect the low anti-caps-PS 19 IgG immune response. Neither did it
have an effect on the rather unpredictable immune response to
caps-PS 4.
|
In vitro effect of blocking CD40L on the IgM Ab response to pneumococcal caps-PS type 19F and type 3
The above described experiments showed that anti-CD40L mAbs
inhibited the Ab response to pneumococcal capsular Ags in vivo. To
investigate whether this inhibitory effect could also be demonstrated
in vitro, spleen cells obtained from BALB/c mice were cultured and
IgM-specific Abs to caps-PS type 3 and type 19F were measured by
ELISPOT assay. Cell cultures in the presence of caps-PS elicited a
clear Ab response (Fig. 3). Addition of
MR1 markedly decreased the number of anti-caps-PS IgM Ab-secreting
cells for caps-PS type 3 as well as for caps-PS type 19F. This
inhibitory effect was dependent on the concentration of the mAb and was
observed with MR1 concentrations between 10 and 40 µg/ml (data not
shown). Addition of hamster IgG did not affect the caps-PS-specific
immune response to PS19F and only slightly inhibited the Ab response to
caps-PS type 3. These studies show that blocking CD40L inhibited the in
vitro Ab response to caps-PS type 3 and type 19F.
|
The previous experiments show that MR1 interfered with the development of the Ab response to caps-PS. However, the mechanism by which anti-CD40L (MR1) treatment suppressed the humoral immune response to polysaccharide Ags was not clear. A series of experiments was performed to explore the possibility that MR1 inhibited the anti-caps-PS immune response by blocking the CD40-CD40L interaction between B cells and CD4+ T lymphocytes.
To address this question, transfer experiments were
performed in which a B lymphocyte fraction or a B lymphocyte fraction
with CD4+ T lymphocytes were transferred to
scid/scid mice. The B lymphocyte fraction was obtained by
removing CD4+ and CD8+
cells from spleen cells. After reconstitution of the
scid/scid mice with either B lymphocytes or B and
CD4+ T lymphocytes, Pneumovax was given and the
effect of MR1 on the IgM Ab formation to caps-PS type 3, 4, 6B, and 19F
was studied. scid/scid mice that received the B cell
fraction and Pneumovax only generated a small Ab response against
caps-PS (Fig. 4). When B lymphocytes and
CD4+ T lymphocytes were transferred into
scid/scid mice, an increase in the IgM Ab titer to the four
serotypes was observed when compared with the condition in which only a
B lymphocyte fraction was transferred. Administration of MR1 inhibited
the CD4+ T lymphocyte-stimulated IgM Ab response
(Fig. 4).
|
In vivo effect of blocking CD40L on the suppressive effect of CD8+ T lymphocytes on the Ab response to pneumococcal caps-PS
In contrast to CD4+ T lymphocytes, which have a stimulatory effect on the anti-caps-PS immune response, CD8+ T lymphocytes have been reported to inhibit the anti-caps-PS immune response (36). Considering the fact that CD8+ cells might also express CD40L, we examined whether blocking the CD40-CD40L interaction would affect the inhibitory effect of CD8+ cells on the caps-PS immune response (37, 38).
Reconstitution of scid/scid mice with murine spleen cells
from which the CD8+ T lymphocyte fraction had
been removed resulted in an enhanced IgM immune response to caps-PS
type 3 when compared with the immune response observed in SCID mice
reconstituted with total murine spleen cells (Fig. 5). These data confirm that
CD8+ T lymphocytes have an inhibitory effect on
the murine immune response to pneumococcal caps-PS.
|
. Transfer of
CD4+ T lymphocyte-depleted murine spleen cells to
scid/scid mice elicited only a weak Ab response. Addition of
MR1 consistently tended to increase the immune response to caps-PS type
3 (p 
0.066) and significantly increased the immune
response to caps-PS type 4. There was no effect on the very weak immune
response to caps-PS type 19F.
|
Finally, the effect of MR1 on the in vitro IgM Ab
formation to caps-PS type 3 and 19F by total murine spleen cells or
murine spleen cells from which CD4+ and/or
CD8+ T lymphocytes had been removed was studied.
The results are shown in Fig. 7. Murine
spleen cells from which CD8+ T lymphocytes had
been removed mounted a higher Ab response than murine spleen cells from
which both CD4+ and CD8+ T
lymphocytes had been removed. This provided evidence that
CD4+ T lymphocytes amplify the anti-caps-PS
Ab response in vitro. Addition of MR1 to the CD8+
T lymphocyte-depleted murine spleen cells markedly decreased the Ab
response, showing that the amplifying effect of
CD4+ T lymphocytes is CD40/CD40L dependent. These
effects were observed for the immune response to caps-PS type 19F as
well as for the immune response to caps-PS type 3.
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Although the mechanisms underlying the noncognate T lymphocyte modulation of the TI immune response are currently a matter of speculation, it is generally believed that the immune response to purified soluble polysaccharides with or without haptenation is independent of the CD40-CD40L interaction (19, 21, 22, 23). In the present manuscript, we critically readdressed the question whether the CD40-CD40L interaction is essential for the regulation of the anti-caps-PS immune response. All previous studies did not unconnectedly consider the interaction between B lymphocytes and CD4+ T lymphocytes and between B lymphocytes and CD8+ T lymphocytes. By carefully and separately investigating the effect of CD4+ T lymphocytes and CD8+ T lymphocytes on the anti-caps-PS immune response and by using MR1, an antagonist mAb against CD40L, we were able to unambiguously demonstrate that the noncognate T lymphocyte modulation of the TI immune response is markedly dependent on CD40L interactions. This interaction not only plays a pivotal role for the IgG response but also for the IgM response.
Our in vitro and in vivo studies illustrated that CD4+ T lymphocytes provide help to the immune response to caps-PS and that this helper function is dependent on CD40L interactions. B lymphocytes in the presence of CD4+ T lymphocytes mounted a notably higher specific immune response to caps-PS than B lymphocytes in the absence of CD4+ lymphocytes. CD8+ T lymphocytes, on the other hand, had a suppressor effect on the immune response to caps-PS. This was demonstrated in vivo by the increased immune response after CD8+ T lymphocyte depletion. CD4+ T lymphocyte-depleted murine spleen cells, leaving a B and CD8+ T lymphocyte fraction, elicited only a weak in vivo and in vitro Ab response. Addition of MR1 to such CD4+ T lymphocyte-depleted murine spleen cells resulted in an increased Ab response. The effect of MR1 was mediated through CD8+ lymphocytes since MR1 exerted no effect on the immune response generated by CD4+ and CD8+ T lymphocyte-depleted murine cells (data not shown).
Collectively, these data provide evidence that CD8+ T lymphocytes inhibit the anti-caps-PS Ab response and support the idea that blocking CD40L on CD8+ T lymphocytes results in opposing the inhibitory effect of CD8+ T lymphocytes on the immune response to anti-caps-PS.
The observation that MR1 did not affect the anti-caps-PS immune response in the absence of CD4+ and CD8+ cells suggested that the effect of MR1 did not depend on the blocking of the CD40-CD40L interaction between B lymphocytes and B lymphocytes, between B lymphocytes and NK cells, or between B lymphocytes and APCs.
Polysaccharides have the capacity to cross-link Ag receptors on the surface of B lymphocytes and induce Ab production. Multivalent membrane cross-linking on the polysaccharide-specific B cell also induces B cell responsiveness to various cytokines and microbial adjuvants for the induction of B cell maturation and Ig class switch. The release of cytokines by T lymphocytes could augment the anti-caps-PS immune response by B cells. We here demonstrate that the CD40-CD40L interaction plays an essential role in the T cell-mediated modulation of the immune response to caps-PS. T cells, once activated, could either directly or indirectly modulate B cell activity via CD40L. Direct ligation of CD40 on B lymphocytes, with subsequent stimulation, is possible. However, an indirect mechanism whereby T lymphocytes interact with APCs cannot be excluded. Contact of T lymphocytes with macrophages and/or dendritic cells through CD40-CD40L interaction could induce the release of multiple cytokines that can further stimulate B lymphocytes.
To our surprise, neutralization of CD40L not only reduced the in vivo IgG immune response, but also resulted in an inhibition of the IgM immune response. A marked inhibitory effect of MR1 on the IgM anti-caps-PS immune response was also demonstrated in vitro. This was unexpected since for T-dependent Ag, CD40-CD40L interaction is important for isotype switch but not for IgM production. Patients with mutations in the CD40L gene do not fail to generate IgM Abs but fall short in producing IgA and IgG Abs. Our observations demonstrate that CD40L interactions are also vital for modulating the IgM response to TI-2 Ags. This might be through a direct effect of T cells on B cells or through an indirect effect, as discussed above.
It is an unresolved question how CD4+ T cells are activated by caps-PS. Polysaccharides do not appear to bind class II MHC molecules (43). One could hypothesize that T cells are triggered by APCs. Through contact with caps-PS, APCs get stimulated and such stimulation could result in the expression of costimulatory molecules and the secretion of various cytokines that can further stimulate T cells. A possible candidate for binding and presenting polysaccharides to T lymphocytes is CD1. This molecule is expressed on dendritic cells and has been described to process and present lipids and glycolipids to T lymphocytes (44, 45).
|
|
Footnotes |
|---|
2 Address correspondence and reprint requests to Dr. Xavier Bossuyt, Laboratory Medicine, University Hospitals Leuven, GHB-Herestraat 49, B-3000 Leuven, Leuven, Belgium. E-mail address: Xavier.bossuyt{at}uz.kuleuven.ac.be
3 Abbreviations used in this paper: caps-PS, capsular polysaccharide; TI, thymus independent; TD, thymus dependent; CD40L, CD40 ligand.
Received for publication September 25, 2001. Accepted for publication January 15, 2002.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
This article has been cited by other articles:
|
|
 |
|
  L. Moens, A. Jeurissen, S. Nierkens, L. Boon, L. Van Kaer, A. Kasran, G. Wuyts, J. L. Ceuppens, and X. Bossuyt Generation of Antibody Responses to Pneumococcal Capsular Polysaccharides Is Independent of CD1 Expression in Mice Infect. Immun., May 1, 2009; 77(5): 1976 - 1980. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Moens, A. Jeurissen, G. Wuyts, P. G. Fallon, B. Louis, J. L. Ceuppens, and X. Bossuyt Specific Intracellular Adhesion Molecule-Grabbing Nonintegrin R1 Is Not Involved in the Murine Antibody Response to Pneumococcal Polysaccharides Infect. Immun., December 1, 2007; 75(12): 5748 - 5752. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. Moens, A. Jeurissen, R. S. Mittler, G. Wuyts, G. Michiels, L. Boon, J. L. Ceuppens, and X. Bossuyt Distinct approaches to investigate the importance of the murine 4-1BB 4-1BBL interaction in the antibody response to Streptococcus pneumoniae J. Leukoc. Biol., September 1, 2007; 82(3): 638 - 644. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Tian, A. Groner, M. Boes, and L.-a. Pirofski Pneumococcal Capsular Polysaccharide Vaccine-Mediated Protection against Serotype 3 Streptococcus pneumoniae in Immunodeficient Mice Infect. Immun., April 1, 2007; 75(4): 1643 - 1650. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Jeurissen, A. D. Billiau, L. Moens, L. Shengqiao, W. Landuyt, G. Wuyts, L. Boon, M. Waer, J. L. Ceuppens, and X. Bossuyt CD4+ T Lymphocytes Expressing CD40 Ligand Help the IgM Antibody Response to Soluble Pneumococcal Polysaccharides via an Intermediate Cell Type J. Immunol., January 1, 2006; 176(1): 529 - 536. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Boudewijns, A. Jeurissen, M. Wuyts, L. Moens, L. Boon, J. J. Van Neerven, A. Kasran, L. Overbergh, C. Lenaerts, M. Waer, et al. Blockade of CTLA-4 (CD152) enhances the murine antibody response to pneumococcal capsular polysaccharides J. Leukoc. Biol., November 1, 2005; 78(5): 1060 - 1069. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Sen, A. Q. Khan, Q. Chen, and C. M. Snapper In Vivo Humoral Immune Responses to Isolated Pneumococcal Polysaccharides Are Dependent on the Presence of Associated TLR Ligands J. Immunol., September 1, 2005; 175(5): 3084 - 3091. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. L. Stephen, M. Niemeyer, A. O. Tzianabos, M. Kroenke, D. L. Kasper, and W. M. Kalka-Moll Effect of B7-2 and CD40 Signals from Activated Antigen-Presenting Cells on the Ability of Zwitterionic Polysaccharides To Induce T-Cell Stimulation Infect. Immun., April 1, 2005; 73(4): 2184 - 2189. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. T. Wang and A. H. Lucas The Capsule of Bacillus anthracis Behaves as a Thymus-Independent Type 2 Antigen Infect. Immun., September 1, 2004; 72(9): 5460 - 5463. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Jeurissen, X. Bossuyt, and C. M. Snapper T Cell-Dependent and -Independent Responses J. Immunol., March 1, 2004; 172(5): 2728 - 2728. [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
) or hamster IgG
(n = 8; 
) on day -1. The IgM immune response to
pneumococcal caps-PS serotypes 3, 4, 14, and 19F were measured 14 days
after immunization. The results show the absorbance values (mean
± 1 SD) at various serum dilutions and are from two independent
experiments. Each experimental group consisted of four animals. *,
Statistically significantly different (p < 0.05)
by Wilcoxon-Mann-Whitney U test.
) of MR1 (500 µg). The B lymphocyte fraction contained
84–89% B lymphocytes and <1.5% CD8+ or CD4+
T lymphocytes. Depletion of only the CD8+ T lymphocytes
resulted in a cell population consisting of mainly B lymphocytes
(54–57%) and CD4+ T lymphocytes (21–31%) with <1.5%
CD8+ cells. The cells were suspended in 0.9% NaCl and
injected i.p. into SCID mice. The total amount of B lymphocytes was the
same for all conditions and amounted to 12 ±
x106. The IgM immune response to caps-PS type 3, 4,
19F, and 6B was measured in duplicate after 14 days (
, murine spleen cells plus Pneumovax). Results shown are
means ± 1 SD of three independent experiments. *, Statistically
significantly different (p < 0.05) by
Wilcoxon-Mann-Whitney U test.
