Characterization and activity of contrasuppressor T cells induced by type III pneumococcal polysaccharide

Optimally immunogenic amounts of type III pneumococcal polysaccharide (S3) activate a population of contrasuppressor T cells (Tcs), which have been shown to play an important role in the induction of anti-S3 antibody responses. These Tcs belong to a unique T cell subset that has the surface phenotype Lyt 1+2- L3T4- I-J+ I-A+. These Tcs are also cyclophosphamide (Cy)-sensitive and sensitive to antilymphocyte serum (ALS) and mitomycin C. Tcs have antigen-binding receptors, indicating that any interactions of Tcs with B cells or T suppressor cells (Ts) (both of which also have antigen-binding receptors) must be via an antigen bridge rather than an idiotype-anti-idiotype interaction. Tcs are also Igh restricted in their action. Contrasuppression is manifest only when the Tcs are Igh compatible with both the Ts and the responding B cells. Tcs apparently mediate their effects by releasing a soluble factor, since a soluble factor extracted from Tcs is able to abrogate the effects of S3-specific Ts.     

Requirement for B cells for activation of contrasuppressor T cells by type III pneumococcal polysaccharide

Type III pneumococcal polysaccharide (S3) is unable to activate S3-specific contrasuppressor T cells (Tcs) in mice depleted of B cells by chronic anti-IgM treatment or in immune defective xid mice that lack the B cell subset required for anti-S3 antibody responses. The inability of S3 to activate Tcs in xid mice was shown to be due to a requirement of B cells for Tcs activation rather than to an absence of Tcs in xid mice. The B cells from normal mice that are required for Tcs activation apparently function to present the S3 Ag to Tcs. S3 physically coupled to spleen cells (S3-SC) prepared from normal BCF1 SC could activate Tcs in both xid and BCF1 mice whereas S3-SC prepared from xid SC or B cell-depleted BCF1 SC could not activate Tcs in either strain. B cell APC function was abrogated by 3000 R irradiation and by treatment of the B cells with either chloroquine or paraformaldehyde. Interestingly, B cells from mice previously immunized with S3 were unable to function in Tcs activation; preimmunization of B cell donors with an irrelevant Ag or with a T-dependent form of S3 had no effect on their ability to function as APC. These latter observations are discussed in terms of the in vivo persistence of polysaccharide Ag and their ability to induce B cell tolerance under the experimental conditions used for these experiments. The results of this study provide evidence that B cells play an important and apparently obligatory role in the activation of Tcs by S3; B cells apparently function to present Ag to Tcs, resulting in the activation of this regulatory T cell subset.     

Distinct populations of antigen-presenting cells are required for activation of suppressor and contrasuppressor T cells by type III pneumococcal polysaccharide

Type III pneumococcal polysaccharide (S3) coupled to spleen cells (S3-SC) has been shown to activate S3-specific Ts and Tcs in mice. Ts activation required I-J identity between carrier SC and Ts donors whereas I-A identity was required for Tcs activation. The carrier SC therefore presumably function as APC for Ts and Tcs activation by S3 since they are apparently not represented by APC present in the Ts and Tcs donors. The properties of the APC required for activation of S3-specific Ts and Tcs were determined by coupling S3 to various spleen cell subpopulations and assessing the ability of the various S3-SC populations to activate Ts and Tcs. The results indicate that Ts and Tcs are preferentially activated when S3 is presented on distinct cell types. S3-specific Ts were activated when S3 was coupled to plastic adherent cells. These cells are nonadherent to anti-Ig and nonfunctional in cyclophosphamide (Cy)-treated mice and their function is eliminated following treatment of cells with either anti-I-A or anti-I-J and C. In contrast, S3-specific Tcs were activated when S3 was coupled to anti-Ig adherent SC which bear I-A and the B cell marker J11d. These cells are functional in Cy-treated mice and their function is resistant to treatment with anti-I-J and C. Thus presentation of S3 on distinct cell types results in the preferential activation of T cells having opposing immunoregulatory function.     

Post-translational regulation of IgM expression in B lymphocytes. Selective nonlysosomal degradation of assembled secretory IgM is temperature-dependent and occurs prior to the trans-Golgi.

B cells express on their surface the membrane form of IgM (mIgM). Upon differentiation, the resulting plasma cells synthesize and secrete large amounts of the secretory form of IgM (sIgM). Surprisingly, B lymphocytes synthesize an excess of secretory mu chain over the expressed membrane mu chain. However, the sIgM is degraded intracellularly, indicating regulation of IgM expression at the post-translational level. In the present report, we show that the assembly, maturation, and degradation of IgM in 38C B lymphocytes are highly accelerated above a certain threshold temperature. Furthermore, the degradation of sIgM is delayed and takes place by the time the maturation of mIgM in the trans-Golgi is almost completed. Neither chloroquine nor monensin has any effect on this degradation, demonstrating a nonlysosomal pre-trans-Golgi process. In addition, the degradation is of endoglycosidase H-sensitive assembled sIgM molecules. We conclude that the degradation of sIgM in 38C B lymphocytes is a postendoplasmic reticulum, pre-trans-Golgi process. We suggest that this degradation process plays a role in the post-translational regulation of expression of soluble lumenal sIgM.     

Requirements for suppressor cell activation. Role of accessory cells

In the 4-hydroxy-3-nitrophenyl acetyl (NP) suppressor system, third order suppressor cells (Ts3) subset of suppressor cells is generated after Ag priming, but, in order to express suppressor activity, these cells need to be further activated or triggered with a specific second order suppressor factor. By in vitro activation of Ts3-containing lymph node cells or a pTs3 hybridoma we now show that macrophages are also required for Ts3 activation. In addition, we demonstrate that IJ genetic restrictions control this activation process. Furthermore, we directly demonstrate Ts3 activation using cloned macrophage hybridoma cells. To further investigate the interactions between Ts3 cells and the accessory cells involved in their activation, we attempted to block the second order suppressor factor mediated activation of Ts3 cells with antibodies. The activation of Ts3 cells can be blocked by the addition of anti-IJ, anti-IJ idiotype or anti-NPb idiotype antibodies, but not by anti-CD8, anti-IA, or anti-IE antibodies. Anti-IJ mAb blocked Ts3 activation at the lymphocyte level whereas anti-IJ idiotype blocked activation at the accessory cell level. Finally we tested, whether these antibodies can also directly activate primed Ts3 cells. We demonstrate that cross-linked anti-IJ, anti-NPb and anti-CD3 antibodies can activate Ts3 cells. The results are discussed in terms of receptor-ligand structures on Ts and accessory cells which are required for the activation of Ts3 cells.     

Antigen-induced Ca2+ signaling and desensitization in B cells

Cross-linking of B cell surface Ig (sIg) by anti-Ig results in transmembrane signaling. However, the capacity of a thymus-dependent (TD) Ag to mediate B cell signal transduction has been less well documented. Therefore, we examined Ag-induced intracellular free calcium concentration [( Ca2+]) in B cells by using TD Ag that would be expected to either cross-link or not cross-link sIgM and/or induce the coupling of sIgM to FcR. Stimulation of mouse TA3 hybridoma B cell transfectants that express the SP6 anti-TNP specific sIgM with either TNP-OVA or anti-IgM antibodies resulted in a maximal fourfold increase in [Ca2+]i. The net increase in [Ca2+]i in response to TNP-OVA was dependent upon both the Ag dose and the TNP:OVA molar ratio. Because occupancy of several cell-surface receptor types leads to a loss of response to subsequent stimulation by ligand (homologous desensitization), we examined the ability of Ag to induce homologous desensitization of sIgM in these B cells. TNP1-OVA at all concentrations tested (up to 500 micrograms/ml) did not lead to any change in [Ca2+]i or desensitization. Cross-linking of TNP1-OVA (10 micrograms/ml) with F(ab')2 of anti-OVA antibody induced both a rise in [Ca2+]i and homologous desensitization of sIg, suggesting that cross-linking of sIgM by Ag is sufficient to induce both these processes. TNP6-OVA at a concentration of 10 micrograms/ml induced changes in [Ca2+]i and partially desensitized TNP-specific B cells to stimulation by anti-IgM. Interestingly, a high dose (180 micrograms/ml) of TNP6-OVA stimulated minimal changes in [Ca2+]i yet did not lead to desensitization. However, cross-linking of TNP6-OVA at this high dose with F(ab')2 of rabbit anti-OVA elevated [Ca2+]i and elicited partial desensitization. Complete desensitization of sIgM by Ag was achieved when intact (Fc-containing) anti-OVA antibody was used, suggesting that the FcR can play a role in desensitization. Ag- and antibody-mediated desensitization was not caused by steric hindrance of sIg. Thus, we have observed two forms of Ag-induced desensitization of sIgM, both of which involve sIg cross-linking and one of which is mediated by the physiologic coupling of sIg to FcR.     

The role of antigen in the activation of regulatory T cells by immune B cells

The transfer of B cells from mice immunized with Type III pneumococcal polysaccharide (SSS-III) results in the activation of suppressor and amplifier T cells that control the magnitude of the antibody response in recipient mice, immunized subsequently with SSS-III. Prior treatment of transferred B cells with an excess of enzyme (polysaccharide depolymerase) capable of hydrolyzing SSS-III, does not alter the capacity of these cells to activate regulatory T cells. These findings indicate that the activation of regulatory T cells by immune B cells is not mediated by residual antigen on the surface of transferred cells.     

Direct demonstration of specific suppressor T cells in the mice tolerant to type III pneumococcal polysaccharide: two-step requirement for development of detectable suppressor cells

Spleen cells from CAF1 mice made tolerant to type III pneumococcal polysaccharide (S3) with S3 coupled to syngeneic spleen cells (S3-SC) develop S3-specific suppressor T cells (Ts). These Ts could be demonstrated consistently only when spleen cells from tolerant mice were cultured in vitro with the specific antigen and the specific tolerogen. Spleen cells from normal mice cultured under the same conditions did not suppress the antibody response to S3. When different numbers of Ts were transferred to normal CAF1 mice, an unusual dose-effect pattern was observed. Maximal suppression of the S3 response occurred when relatively low numbers of Ts, 3 to 30 x 10(5) per recipient, were transferred, whereas larger numbers of cells, 150 x 10(5) per recipient, were not suppressive. These results indicate that a presumably T-independent antigen, S3, can activate antigen-specific Ts. These Ts exhibit unusual dose effects upon transfer and require both an in vivo induction period and in vitro activation for development of maximal activity. These latter observations suggest that S3 may activate a different population of T cells with suppressor function than do conventional T-dependent antigens. The loss of suppression observed when greater than optimal numbers of cells were transferred suggests that a second type of T cell, which has the ability to 'neutralize' the activity of S3-specific Ts, is also induced in the same spleen cell population.     

Rejection of skin allografts by CD4+ T cells is antigen-specific and requires expression of target alloantigen on Ia- epidermal cells

The effector mechanism of skin allograft rejection has been characterized as Ag specific, rejecting cells that express the target alloantigen but sparing those that do not. However, the rejection of MHC class II disparate skin grafts, in which very few cells (Langerhans cells) actually express the target Ia Ag could conceivably proceed by either one of two distinct rejection mechanisms. One possibility is that Ia- cells are destroyed by a sequence of events in which CD4+ T cells, activated by Ia+ LC, elaborate soluble factors that are either directly cytolytic or that recruit and activate non-specific effector cells. The alternative possibility is that activated CD4+ T cells elaborate soluble factors which induce Ia expression on Ia- cell populations, and that these Ia+ cells are subsequently destroyed by effector cells specific for the induced Ia alloantigens. We found that rejection of Ia+ LC was not of itself sufficient to cause rejection of skin grafts, indicating that skin allograft rejection is contingent on the destruction not only of LC but of other graft cell populations as well. We then investigated whether CD4+ T cells rejected allogeneic skin grafts in an antigen specific fashion. To do so, we engrafted immunoincompetent H-2b nude mice with trunk skin grafts from B6----A/J allophenic mice because such skin is composed of mutually exclusive cell populations expressing either H-2a or H-2b histocompatibility Ag, but not both. The engrafted mice were subsequently reconstituted with H-2b CD4+ T cells. The CD4+ T cells destroyed keratinocytes of A/J origin but spared keratinocytes of B6 origin, even though neither cell population constitutively expresses target IAk alloantigen. The targeted rejection of A/J keratinocytes but not of B6 keratinocytes indicates that the target Ia alloantigen must have been induced on Ia- A/J keratinocytes, rendering them susceptible to destruction by anti-Iak-specific CD4+ effector cells. These data demonstrate that CD4+ T cell rejection of skin allografts is mediated by Ag-specific CD4+ cytolytic T cells and hence, requires the induction of target Ia alloantigens on epidermal cells within the graft.     

Transferred B cells from autoimmune NZB/N mice fail to activate T suppressor cells

T-cell-mediated suppression of the antibody response of autoimmune NZB/N mice to Type III pneumococcal polysaccharide (SSS-III) can readily be induced in situ by priming with a subimmunogenic dose of SSS-III; however, the transfer of either "young" (8 weeks old) or "old" (42 weeks old) SSS-III-primed B cells, which activates suppressor T cells in normal BALB/cByJ mice, fails to induce suppression of the antibody response in recipient NZB/N mice, regardless of the number of cells transferred or the time interval between transfer and immunization. Transfer of 51Cr-labeled B cells demonstrated that syngeneic primed B cells home to the spleens of NZB/N mice in somewhat lower numbers than in BALB/cByJ mice, although the differences observed may not be sufficient to explain the complete absence of activation of suppressor T cells. These findings suggest that B cells from autoimmune NZB/N mice are unable to activate T suppressor cells upon transfer; this disorder in a normal regulatory mechanism may be important in the pathogenesis of disease.     

Activation of B cells by autoreactive T cells: cloned autoreactive T cells activate B cells by two distinct pathways

Although the existence of autoreactive T cells has been widely reported, the functional capacities of these populations have been less well defined. Studies were therefore carried out to characterize the relationship of autoreactive T cells to antigen-specific major histocompatibility complex (MHC)-restricted T cells in their ability to act as helper cells for the induction of immunoglobulin synthesis by B cells. A number of autoreactive T cell lines and clones were isolated from antigen-primed spleen and lymph node cell populations. Autoreactive T cells were found to proliferate in response to direct recognition of syngeneic I-A or I-E subregion-encoded antigens in the absence of any apparent foreign antigen. It was shown that cloned autoreactive T cells were capable of activating B cell responses through two distinct pathways. After appropriate stimulation by syngeneic cells, autoreactive T cells polyclonally activated primed or unprimed B cells to synthesize IgM antibodies. These activated T cells functioned in these responses through an MHC-unrestricted pathway in which polyclonal responses were induced in both syngeneic and allogeneic B cells. These cloned autoreactive T cells were also able to activate IgG responses by primed B cells through a different activation pathway. In contrast to the polyclonal activation of IgM responses, the induction of IgG antibodies by the same cloned T cells required primed B cells and stimulation with the priming antigen. The activation of B cells to produce IgG was strongly MHC restricted and required the direct recognition by the autoreactive T cells of self MHC determinants expressed on the B cell surface, with no bystander activation of allogeneic B cells. These results indicate that cloned autoreactive T cells resemble antigen-specific MHC-restricted T cells in their ability to function as T helper cells through distinct MHC-restricted and MHC-unrestricted pathways.     

Phenotypic analysis of pneumococcal polysaccharide-specific B cells

The phenotype of B cells responsible for the production of anti-pneumococcal polysaccharide Ab has been unclear. Although individuals that respond poorly to the 23-valent pneumococcal polysaccharide (PPS) vaccine, Pneumovax, such as children <2 y, the asplenic, and a subset of common variable immunodeficiency patients, are profoundly deficient or lack IgM memory cells (CD27(+)IgM(+)), they are also deficient in the switched memory (CD27(+)IgM(-)) compartment. Direct characterization of PPS-specific B cells has not been performed. In this study, we labeled PPS14 and PPS23F with fluorescent markers. Fluorescently labeled PPS were used in FACSAria flow cytometry to characterize the phenotype of PPS-specific B cells obtained from 18 young adults pre- and postimmunization with Pneumovax. The labeled PPS were capable of inhibiting binding of Ab to the native PPS. Similarly, the native PPS were able to inhibit binding of PPS-specific B cells in a flow cytometric assay demonstrating specificity and functionality. Phenotypic analysis of unselected B cells, pre- and postimmunization, demonstrated a predominance of naive CD27(-)IgM(+) cells accounting for 61.5% of B cells. Likewise, the PPS-specific B cells obtained preimmunization consisted primarily of naive, CD27(-) B cells, 55.4-63.8%. In contrast, the PPS-specific B cells obtained postimmunization were predominantly IgM memory cells displaying the CD27(+)IgM(+), 54.2% for PPS14 and 66% for PPS23F, significantly higher than both unselected B cells and PPS-specific B cells. There was no significant difference in switched memory B cell populations (CD27(+)IgM(-)) between groups. These results suggest a dominant role of IgM memory cells in the immune response to pneumococcal polysaccharides.     

Expression, distribution and specificity of Fc receptors for IgM on murine B cells

Subpopulations of normal adult murine splenic B cells and a panel of murine B cell tumors were examined for their ability to bind murine IgM specifically. By using two-color flow cytometric analyses, we have demonstrated that 90 to 95% of surface (s)IgD+ B cells express surface membrane receptors for IgM (Fc mu R). The binding of pentameric murine IgM to splenocyte Fc mu R was IgM-specific since it was totally inhibited by other polymeric IgM proteins, but not by Ig of other H chain classes or by mAb specific for the murine IgG or IgE FcR. Binding of IgM to splenic cells was saturable. Fc mu R were co-expressed with the Fc gamma R as well as the Fc epsilon R on the majority of splenic B cells. Minor populations of splenic mononuclear cells expressed only an Fc mu R, Fc gamma R or Fc epsilon R. In a survey of B tumor cell lines representing different stages of B cell development, we observed that the Fc mu R was expressed on pre-B cell lines and that Fc mu R detection was maximal on immature B cell lines that expressed sIgM and low amounts of sIgD and Ia. Fc mu R were not detected on cell lines that had switched from sIgM to the expression of another sIg, or on plasmacytomas and hybridomas. The studies with normal splenocytes establish that the majority of sIgD+ B lymphocytes in adult BALB/c mice express surface membrane receptors that specifically bind IgM. The studies with B lineage tumor cells suggest that the expression of Fc mu R on B cells is developmentally regulated and that the pattern of expression exhibited by Fc mu R during B cell ontogeny differs from the patterns that have been previously found for IgG and IgE FcR. These observations raise the possibility that Fc mu R might have a functional significance in some aspect of B cell maturation and activation. By using a family of IgM H chain constant region domain deletional mutants, we have further demonstrated that, like the T cell Fc mu R, the B cell Fc mu R also requires a C mu 3 domain for binding to occur, raising the possibility that the T and B cell Fc mu R in mice may be structurally related molecules.     

Pre-B cells: bone marrow persistence in anti-mu-suppressed mice, conversion to B lymphocytes, and recovery after destruction by cyclophosphamide.

Chronic treatment of mice from birth with anti-mu antibodies aborts development of B lymphocytes and plasma cells. In these studies we show that bone marrow from anti-mu-treated mice contains a population of cells with cytoplasmic IgM, but which lack detectable cell-surface IgM. These cells are analogous to pre-B cells, defined in ontogenetic studies as the immediate precursors of B lymphocytes. Pre-B cells from bone marrow of anti-mu treated mice retain their functional integrity, as evidenced by their ability to give rise to sIgM+, LPS-responsive lymphocytes in culture. We also show that cyclophosphamide treatment destroys pre-B cells and that recovery of pre-B cells in bone marrow precedes the regeneration of sIgM+ B lymphocytes. Generation of B lymphocytes in adult mice apparently occurs exclusively in the bone marrow because induction of extramedullary hemopoiesis in spleen was not accompanied by the appearance of pre-B cells in that organ.     

Polymerization of secretory IgM in B lymphocytes is prevented by a prior targeting to a degradation pathway.

B lymphocytes express on their surface a membrane form of IgM (mIgM), and synthesize but fail to secrete a secretory form of IgM (sIgM). Plasma cells shift to the exclusive synthesis and efficient secretion of sIgM. The sIgM in B cells differs from that in plasma cells in its pattern of assembly: in plasma cells, monomers of sIgM are assembled into polymers and only polymers are secreted; in B lymphocytes, monomeric sIgM is neither polymerized nor secreted and is degraded intracellularly. In this article we blocked the export of proteins from the endoplasmic reticulum at low temperatures or with energy poisons or brefeldin A, and localized the different assembly steps of mIgM and sIgM in the 38C B lymphocytes and of sIgM in the 38C-derived sIgM-secreting D2 hybridoma. In both cell lines, sIgM assembly into monomers was not affected, whereas polymerization of sIgM in D2 cells and monomer formation of mIgM in 38C cells were strongly inhibited. Moreover, probing with specific lectins revealed galactosylated monomers and polymers in D2 cells and galactosylated hemimer and monomers only of mIgM in 38C cells. In addition, when Golgi functions were hampered with Tris base, monomerization of mIgM and polymerization of sIgM were attenuated. These results indicate that polymerization of sIgM in D2 cells and monomerization of mIgM in 38C cells are post-endoplasmic reticulum events, occurring in or beyond the trans-Golgi galactosylation compartment. Since only polymers are secreted from D2 cells and only monomeric mIgM is displayed on the surface of 38C cells, partially assembled molecules may traverse the secretory pathway yet are restricted from the cell surface. Furthermore, monomeric sIgM in 38C cells is never galactosylated, thus it is degraded prior to the galactosylation compartment. We conclude that targeting of sIgM to degradation in 38C cells precedes its assembly site into polymers in D2 cells. This implies that degradation of sIgM does not result from the incompetence of 38C cells to polymerize. Rather, assembly of sIgM into polymers and their subsequent secretion are prevented in B lymphocytes by preceding targeting of monomeric sIgM to degradation.     

Suppression of IgM responses to type III pneumococcal polysaccharide by lipopolysaccharide (LPS).

Lipopolysaccharide (LPS) suppressed the primary IgM response of mice to Type III pneumococcal polysaccharide (S3). LPS and S3 had to be given together in order for maximum suppression to occur and suppression was not due to a change in the time of the peak response in mice which received LPS. Suppression was not due to an effect of LPS on T cells since S3 responses of nude mice were suppressed by LPS. LPS did not suppress S3 responses of C₃H/HeJ mice and base hyrolysis of LPS destroyed the suppressive effect, i.e., suppression was dependent of B cell mitogenic activity of the LPS. The suppressive effect of LPS was presumably directed against virgin B cells since LPS did not suppress the S3 response of primed mice and did not suppress the development of IgG memory responses to S3.     

Regulation of IgM expression by adjuvant activated splenic suppressor T cells

Adjuvant-activated Lyt-2 positive suppressor T cells (Ts) are able to inhibit the expression of IgM plaque-forming cells (PFC) during a primary in vitro response to sheep red blood cells. Under the same experimental conditions these suppressor T cells do not affect a secondary IgM PFC response against SRBC. Activated Ts cells were also found to suppress the spontaneous IgM secretion of cultured B cells as well as the IgM production of B cells stimulated by lipopolysaccharide or by supernatant from a T-helper-cell clone.     

Human polysaccharide-specific B cells are responsive to pokeweed mitogen and IL-6

The responsiveness of polysaccharide-specific B cells to PWM was examined in vitro. Spleen cells from six patients immunized with Haemophilus influenzae type b-diphtheria toxoid, pneumococcal and meningococcal vaccines were T cell-depleted and separated by Percoll density gradient centrifugation. In each B cell fraction, spontaneous antibody production was demonstrated to capsular polysaccharides as well as diphtheria toxoid. The peak of spontaneous antibody production was demonstrated to be five to seven days after immunization. When T cells and PWM were added, the total Ig secretion increased in all B cell fractions. PWM also enhanced IgG antibody directed to each of three polysaccharide Ag measured. This enhancement was most noticeable for nonresting B cells. The PWM effect was not confined to IgG, as IgM and IgA to Neisseria meningitidis type C were measured and also enhanced. The kinetics of the PWM response demonstrated the most IgG antibody to polysaccharide Ag from spleens immunized five to seven days before splenectomy. When the patients were immunized either 2 days or 4 mo before splenectomy, no spontaneous IgG antibody to polysaccharides was detected although PWM induced small amounts of antibody. Finally, anti-IL-6 antibody blocked PWM-induced total and polysaccharide-specific antibody production. We conclude that human polysaccharide-specific B cells are responsive to PWM and IL-6. We suggest that polysaccharide B cells are not truly "T cell-independent" and may respond to T cell lymphokines and thus are similar to protein-specific B cells.     

T cells recognizing polysaccharide-specific B cells function as contrasuppressor cells in the generation of T cell immunity to Pseudomonas aeruginosa

The cellular interactions involved in the development of T cell-mediated immunity to Pseudomonas aeruginosa have been examined. T cell immunity can be generated by immunizing mice with 10 micrograms of P. aeruginosa polysaccharide (PS) plus the antimitotic agent vinblastine sulfate. Vinblastine is required to inactivate a population of Ts cells generated by immunization with 10 micrograms of PS alone. Immunization with either live bacteria or with higher dose (50 micrograms) of PS without vinblastine also generates T cell immunity; these protocols activate a population of Lyt-1+, 2-, I-J+ T cells which, like vinblastine, counteract the effect of Ts cells. Immunization with 10 micrograms PS alone fails to activate this T cell subpopulation. When administered at the time of immunization, this subpopulation can render the tolerogenic 10-micrograms immunization protocols immunogenic. Like previously described contrasuppressor T cells, this T cell subpopulation exhibits an affinity for the lectin Vicia villosa. We have determined, however, that the T cells that act as contrasuppressor cells in this system are directly activated by PS-immune B cells and not by PS Ag. Furthermore, their activity can be removed by adsorption to PS-specific B cell hybridomas. Our studies indicate an important role for B cells in the development of T cell immunity to P. aeruginosa and suggest that a complex idiotype network controls the development of this response.     

Antigen-induced T suppressor cells regulate the autoreactive T helper-B cell interaction

The T suppressor (Ts) cell population that functions to regulate antigen-specific MHC-restricted T helper (Th)-B cell interactions also regulates the activation of B cells by cloned autoreactive Th cells. Activated Ts cells were generated by in vivo priming and restimulation in vitro with high concentrations of the specific priming antigen. Once generated, this Ts population inhibits the Th-dependent activation of primed B cells by both antigen-specific and autoreactive T cells in an antigen-nonspecific manner. This suppression requires the participation of both Lyt-1+2- and Lyt-1-2+ T cells. It was also demonstrated that accessory cells were required for the induction of Ts cells. Moreover, the generation of suppression was MHC-restricted and required the recognition by T cells of Ia antigens on accessory cells. These studies demonstrate that the same or a very similar Ts cell population can function to inhibit the activation of B cells by antigen-specific as well as autoreactive T cells.