Two distinct types of helper T cells involved in the secondary antibody response: independent and synergistic effects of Ia- and Ia+ helper T cells

Defective induction of antigen-reactive proliferating T cells in B cell-deprived mice

Mice were injected from day of birth onward with rabbit anti-mouse IgM antiserum or purified rabbit anti-mouse IgM antibodies. These mice completely lacked Ig-positive cells or serum Ig, as analyzed by specific fluoresceinated antibodies on the fluorescence-activated cell sorter (FACS-II), by polyclonal B cell mitogens and by specific precipitation in agar. These animals were then primed in vivo by antigen emulsified in complete Freund's adjuvant, and, subsequently, their draining lymph nodes were tested for their T cell proliferative responses in vitro, to the relevant antigen and were found to be severely impaired. However, the antigen-presenting capacity of both spleen cells and thioglycollate-induced peritoneal cells was found to be intact.

Regulation of delayed-type hypersensitivity. VII. The role of I-J subregion gene products in the inhibition of delayed-type hypersensitivity to major histocompatibility antigens by specific suppressor T cells

Suppressor T cells for delayed-type hypersensitivity (DTH) to alloantigens are induced by injecting mice intravenously with a high dose of X-irradiated allogenic cells. Using the same protocol, suppression of DTH directed against H-2 subregion products could also be induced, provided that the H-2 incompatibility between the cells used for the induction of suppression and the recipients includes the I-J subregion genes. Thus, the I-J subregion difference is both necessary and sufficient for the induction of suppression of DTH to the whole or part of the H-2 gene products. The suppression appears to be mediated by antigen-specific suppressor T cells which recognize the allo-I-J molecules and are able to suppress the DTH response to other H-2 subregion gene products in an associative recognition manner. T cells from (B10 x BALB/c)F1 mice suppressively primed against B10.A(5R) cells (directed against JkEk antigens), when adoptively transferred to normal syngeneic recipients, were capable of suppressing the hosts' DTH response to B10.A(4R) cells (KkAk antigens) when the recipients were challenged with [B10.A(4R) x B10.A(5R)]F1 cells (KkAk x JkEk). The recipients express normal DTH reactivity to B10.A(4R) cells when challenged with a mixture of B10.A(4R) cells (KkAk + JkEk). These results provide direct evidence that when functioning as alloantigens, the I-J determinants preferentially induce suppressor T cells which specifically impair the immune response to the I-J molecules as well as other H-2 gene products if they are physically associated with the I-J determinants. The role of I-J subregions as the suppressor genes is discussed in terms of the possible application in transplantation immunity and the host's defence against infectious diseases.

Analysis of antigen-specific, Ig-restricted cell-free material made by I-J+ Ly-1 cells (Ly-1 TsiF) that induces Ly-2+ cells to express suppressive activity

A set of T cells defined by a unique profile of cell surface alloantigens (phenotype Ly-1+2-; Qa-1+; I-J+) produces biologically active cell-free material(s) (Ly-1 TsiF) which induces another T cell set (cell surface phenotype Ly-1,2+; I-J/; Qa-1+) to participate in the suppression of primary immune responses to heterologous erythrocytes. The suppression is specific for the inducing antigen, and the Ly-1 TsiF binds antigen in a specific way. The activity of Ly-1 TsiF can be removed by anti-I-J immunosorbents and will not be expressed if the functional producer and acceptor cells do not share gene products that are encoded in or are tightly linked to the VH portion of the Ig complex. There is no requirement for the Ly-1 TsiF and its acceptor cell(s) to share major histocompatibility complex gene products. Thus, for optimal induction of antigen-specific suppression by cell-gree materials from Ly-1 T cells, three necessary conditions must be met: (a) antigen recognition by Ly-1 TsiF; (b) the expression of I-J gene products and (c) identify of VH-linked Ig locus gene products (or other products influenced by those genes) on both the inducer molecule and its acceptor cell. The role of the Ig-linked restriction is particularly intriguing, and its possible meaning is considered in detail.

Regulation of immune responses by I-J gene products. I. Production and characterization of anti-I-J monoclonal antibodies

Using a novel, two-step functional screening procedure, we have isolated hybridoma B cell lines secreting monoclonal antibodies directed against gene products of the I-Jb and I-Jk subregions of the mouse H-2 complex. These monoclonal antibodies act in vitro by allowing nonresponder spleen cells to respond to normally suppressive quantities of poly(Glu50Tyr50) (GT) (WF8 series of anti-I-Jk monoclonal antibodies) or to suboptimal concentration of poly(Glu60Ala30Tyr10) (WF9 series of anti-I-Jb monoclonal antibodies). Some of the culture supernates that show augmenting activity bind GT-specific T cell-derived suppressor factor (GT-TsF), indicating that some monoclonal antiantibodies display a nonspecific enhancing effect, or, more likely, that anti-I-J monoclonal antibodies have been produced against I-J determinants not found on TsF. It is this last possibility that is most intriguing and that might serve as a means for exploring the heterogeneity of the I-J subregion. It is also possible that some of our monoclonal anti-I-J antibodies might detect antigenic determinants selectively expressed on suppressor T cells, helper T cells, and/or macrophages. In addition, we have demonstrated that monoclonal anti-I-J antibodies should be useful in the biochemical characterization and purification of a monoclonal GT-TsF. These haplotype-specific anti-I-J monoclonal antibodies should prove to be powerful tools for future studies exploring the role of I-J gene products in the regulation of specific immune responses.

Monoclonal antibodies that recognize the product controlled by a gene in the I-J subregion of the mouse H-2 complex

The B cell hybridomas producing monoclonal antibodies (E10, D7, F4, H6, and D4) were established by the fusion of P3U1 or NS-1 murine myeloma cell lines and spleen cells of B10.A(5R) mice hyperimmunized with mitomycin C-treated B10.A(3R) spleen and thymus cells. Two types of monoclonal antibodies specific for the products controlled by a gene in the I-Jb subregion of the H-2 complex were characterized: one specific for the private type of I-Jb determinant, the other recognizing the cross-reactive determinant between the I-Jb and I-Jd products. By using these monoclonal reagents, the I-J-encoded product on the antigen-specific suppressor T cells was found to be expressed on their soluble suppressor factors. Furthermore, the I-Jb products were successfully detected not only on the T cell hybridoma with suppressor activity specific for keyhole limpet hemocyanin (KLH), but also on KLH-primed suppressor T cells enriched by antigen-coated petri dishes and concanavalin A-induced thymocyte blasts of C57BL/6 mice by complement-dependent cytotoxic assays and membrane fluorescence techniques.

In vitro generation of antigen-specific hemolytic plaque-forming cells from human peripheral blood mononuclear cells

We have described a culture and assay system for the sensitization of human peripheral blood mononuclear cells with a T cell-dependent antigen, sheep erythrocytes, in the absence of nonspecific stimulatory agents and with the subsequent generation of macroscopic hemolytic plaques. We have shown that the antibody produced by the plaque-forming cells generated in this culture system is specific for the sensitizing antigen, and that the plaques created are not false plaques because their formation is inhibited by cycloheximide. The success of this system can be attributed to several critical factors including large numbers of peripheral blood mononuclear cells (5 x 10(6) culture), a prolonged period of incubation (10-11 d), continuous rocking during the entire period of incubation, culturing in large (35-mm) flat-bottomed culture dishes in the presence of human plasma, and the appropriate antigen concentration (5 x 10(6) sheep erythrocytes/culture). Furthermore, the generation of macroscopic hemolytic plaques requires plaquing sensitized peripheral blood mononuclear cells in target cell monolayers fixed in an agarose matrix with an incubation period of 2-3 h. We have further shown that the antigen-specific response measured by this system is dependent on adherent cells and T lymphocytes. At least one population of the helper T cells is sensitive to 2,000 rad irradiation. This system is simple, sensitive, and should serve as an effective tool for the analysis of cellular interactions involved in the generation of human antigen-specific plaque-forming cells, the genetic control the human immune response, and the pathophysiology of altered immunoregulation in disease.

Functional helper activity of monoclonal T cell populations: antigen-specific and H-2 restricted cloned T cells provide help for in vitro antibody responses to trinitrophenyl-poly(LTyr,Glu)-poly(DLAla)--poly(LLys)

The ability of long-term cultured and monoclonal T cell populations to provide antigen-specific help was assessed in a system of Ir gene-controlled in vitro antibody responses to soluble antigens. T-cell colonies and monoclonal T-cell lines were generated which proliferated specifically in response to poly(LTyr,Glu)-poly(DLAla)--poly(LLys) [(T,G)-A--L] and were I-A restricted in these proliferative responses. These (T,G)-A--L-specific T-cell populations were evaluated for their ability to help unprimed and T-cell depleted spleen cell populations in the generation of antibody responses to trinitrophenyl (TNP)-(T,G)-A--L in vitro. It was found that long-term T-cell lines, including monoclonal T-cell populations derived by limiting dilution, were highly efficient helper cells for IgM responses to TNP-(T,G)-A--L. These helper T cells were both antigen-specific and I-A restricted in their ability to be activated and to cooperate with T-cell depleted spleen cell populations. Once specifically activated, however, these clones provided help that was antigen nonspecific. These studies have thus demonstrated the ability of antigen-specific and H-2-restricted monoclonal T-cell populations to provide help for responses to soluble antigens in vitro.

T cell regulation of isotype expression. The requirement for a second Ig-specific helper T cell population for the induction of IgG responses

A characteristic of the in vivo responses to T-dependent antigens is the highly restricted expression of Ig heavy chain classes of both the antibody and nonspecific Ig produced. To investigate the cellular interactions which regulate expression of Ig class, sheep red blood cell- and keyhole limpet hemocyanin-primed BALB/c T cells were tested in vitro for their ability to induce normal BALB/c B cells to selective Ig secretion. The results, based initially on linear regression analysis, indicate that while the production of IgM required help from a single antigen-specific helper cell, additional signals from a second pool of helper cells were necessary for the expression of IgG isotypes. The greatly diminished ability of primed T cells from mice suppressed from birth for IgM production to induce IgG responses indicated that the generation of this second class-regulating T cell pool requires the presence of Ig, probably B cell-presented, during the period of priming. Bases on the present data, secretion of IgG by normal B cells can be explained by invoking the requirement for a second pool of helper T cells which recognize Ig determinant, in contrast to the I region recognition known to exist for effective help by the first helper cell. In addition, it is proposed that in the absence of such a second signal only IgM secretion will occur.

Generation of immunoglobulin secreting cells in mixed lymphocyte culture

The nature of the cellular interactions and role of the HLA system in the generation of immunoglobulin secreting cells in primary and secondary mixed lymphocyte cultures were investigated. The B lymphocyte response to alloantigen stimulation as measured by a Protein A reverse hemolytic plaque assay, consisted of polyclonal activation with production of IgG, IgM, IgA secreting cells detectable as early as day 4 in a primary and by 24 hr in a secondary mixed lymphocyte culture. B cell activation was shown to be dependent upon collaboration with T helper cells. A disparity at the HLA D/DR region between responding and stimulating cell populations was required for the induction of T helper cells. However, once activated, T helper cells could collaborate with autologous or allogeneic B lymphocytes and, without additional antigen, trigger immunoglobulin production. The mixed lymphocyte culture may now be considered a model of B cell as well as T cell activation.

Antigen-specific helper T cells required for dominant idiotype expression are not H-2 restricted

Two synergizing antigen-specific helper T (Th) cell populations are required for an optimal TEPC15 (T15)-dominated antiphosphorylcholine (PC) plaque- forming cell response . In these studies, the two Th cell sets are shown to differ in their requirements for recognition of self-major histocompatibility complex (MHC)-encoded determinants by testing the ability of Th cells from F(1) {arrow} parent bone marrow chimeras to collaborate with PC-specific B cells bearing MHC-encoded determinants of either parental haplotypes. Previous studies have shown that one antigen-specific Th cell population is required for T-dependent anti-PC responses and activates PC-specific B cells only if the hapten, PC, is physically linked to the priming antigen. This Th cell, referred to as ThMHC, induces anti-PC responses that are mainly non-T15 in character, and it appears to be identical to the conventional antigen- specific Th cell. In these experiments, using T cells from (A X B)F(1) {arrow} parent A chimeras, ThMHC cells requiring hapten-carrier association provide help for F(1) and parent A B cells but not for B cells from parent B, thus confirming that the activity of the conventional Th cell is H-2 restricted . The second antigen-specific Th cell population, whose function is measured in the presence of the ThMHC cell set, preferentially activates T15-bearing B cells. This Th cell set (ThId) is missing in mice expressing low levels of T15-bearing antibody and can be restored by the addition of antigen-specific T cells from donors expressing high levels of circulating T15 Id. These studies demonstrate that T cells from F(1) {arrow} parent chimeras that express substantial levels of T15-bearing anti-PC antibody could provide ThId cell activity for the selective activation of T15-bearing B cells of F(1) and both parental H-2 types. These results imply that whereas the activity of conventional, ThMHC, cells is clearly H-2 restricted, ThId cells from the same chimeric donors are not required to recognize antigen in association with self-MHC-encoded determinants for successful T-B collaboration .

Haplotype-specific suppression of antibody responses in vitro. II. Suppressor factor produced by T cells and T cell hybridomas from mice treated as neonates with semiallogeneic spleen cells

Culture supernatant fluids from spleen cells from C57BL/10 or BALB/c mice neonatally treated with semiallogeneic (B 10.D2 x B10)F1 cells to induce haplotype-specific suppressor T cells and restimulated with macrophages syngeneic at I-A with the allogeneic haplotype encountered as neonates contain a soluble factor capable of suppressing primary in vitro antibody responses of normal syngeneic spleen cells in a non-antigen-specific manner. This haplotype-specific suppressor factor, TsF-H, has also been recovered in culture fluids of a T cell hybridoma produced by fusion of the AKR thymoma BW5147 and the haplotype-specific suppressor T cells. TsF-H is inactivated by low pH (3.5) trypsin, for 30 min at 50 degrees C, and has a molecular weight in the range of 45,000 to 68,000. Studies with specific immunoabsorbents demonstrate the presence of determinants encoded by the I-A subregion of the haplotype of the T cell producing TsF-H but not I-J subregion or immunoglobulin constant-region determinants on the TsF-H. Suppression is restricted to primary in vitro antibody responses, and not secondary antibody, mixed lymphocyte, or cytotoxic lymphocyte responses by spleen cells syngeneic at the I-A subregion of H-2 with the T cell producing the factor. The properties and activities of TsF-H and the haplotype-specific suppressor T cell are compared and contrasted with antigen-specific and genetically restricted suppressor T cells and their factors.

Individual clones of carrier-specific T cells help idiotypically and isotypically heterogeneous anti-hapten B-cell responses

We have established lines and clones of helper T cells specific for the antigen fowl gamma globulin (FGG) and maintained these cells in continuous proliferation in vitro for up to 8 months. During this period the specific helper activity was assessed in vitro in T cell-dependent anti-hapten responses. These pure populations of FGG-specific helper T cells provide help in the absence of other T cells for the induction of B cells to produce specific antibody of different isotypes and idiotypes. The same clones of specific helper T cells can provide help for a T cell-dependent antibody response against azobenzene arsonate (ARS), dinitrophenol (DNP) or phosphorylcholine (PC). With the exception of one clone all FGG-specific helper T cells (TFGG) promoted anti-hapten responses only when the hapten was covalently bound to the specific carrier. Help was only provided when T cells and T-depleted spleen cells were H-2 compatible to the left of the I-B region.

Contrasuppression. A novel immunoregulatory activity

We have described an interaction between two T cells subsets that results in interference with the expression of Ly-1-, 2+ (Ly-2) T cell-mediated suppression. We refer to this novel immunoregulatory activity as contrasuppression. The T cell responsible for the induction of contrasuppression (inducer cell) expresses the phenotype Ly-1-, 2+;I-J+;Qa-1+. This phenotype distinguishes it from the suppressor effector cells which we find to be I-J-2.3. An I-J+ soluble mediator from the contrasuppressor inducer cell acts on another cell (acceptor cell) that expresses the phenotype Ly-1+, 2+; I-J+; Qa-1+. This phenotype distinguishes it from T helper cells. Both the inducer cell (or its biologically active mediator) and its acceptor cell are required for the expression of contrasuppression. Because contrasuppressor cells can block the suppressive activity of cell-free mediators released by Ly-2 suppressor T cells, the mechanism of contrasuppression is either separated from or in addition to the inactivation of suppressor cells themselves. The potential importance of contrasuppressor activity in the regulation of suppressor T cell activity in allowing immunologic memory to be expressed and in permitting microenvironmental immune regulation is discussed.

Major histocompatibility complex restriction of soluble helper molecules in T cell responses to altered self

Evidence for major histocompatibility complex (MHC) restriction of soluble helper effects was observed in the generation of syngeneic killer T cells to trinitrophenyl-altered self. Ia-bearing T cells obscure the observation of such interactions, thus, must be removed to detect MHC restriction of nonspecific soluble helper factor supernates (HFS). Genetic mapping studies demonstrated that the strain producing HFS must be compatible in the H-21A region with the strain utilizing the helper molecules for optimal helper signals to be delivered.

Influence of Igh-linked gene products on the generation of T helper cells in the response to sheep erythrocytes

The role of Igh-linked loci in the generation and expression of T cell help for antibody responses to sheep erythrocytes (SRBC) was investigated. The production of IgM, IgG3, IgG1, IgG2b, and IgG2a antibody to SRBC was shown to be T cell dependent. The Igh-congenic mouse pair CBA/Tufts (Ighj) and CBA.Ighb gave equivalent responses to SRBC. CBA.nude mice (Ighj) supplemented with peripheral T cells of either Ighj or Ighb genotype produced equivalent, high responses. Therefore, T cell-B cell mismatching for the Igh haplotype is not in itself a bar to the generation or expression of help. In contrast, T cells primed in an environment that lacks Ighj-linked products are inefficient helpers for Ighj B cells. These results suggest that antigen-primed B cells or their products prime a set of T cells that can help B cells that bear matching, Igh-linked gene products.

Effect of helper T cells on the primary in vitro production of delayed-type hypersensitivity to influenza virus

Injection of mice with infectious or noninfectious preparations of influenza virus induces the formation of T cells which, when added to primary tissue cultures of normal spleen cells exposed to influenza virus, enhance the generation of effector T cells which mediate delayed-type hypersensitivity (DTH) reaction. The enhancing cells possess Thy-1 and Ly-1 surface antigens are radioresistant and antigen-specific. If infectious virus was used to stimulate the DTH response in vitro, help was delivered whether homologous or heterologous A strain influenza virus was used to generate the helper T cells (Th) in vivo. In contrast, only Th cells generated using homologous virus were effective if noninfectious virus was used to stimulate the DTH response in vitro. Peak helper activity occurred 2 d after virus injection and the Th cells were only effective if added to the primary cultures within 24 h after addition of the stimulating antigen. The Th cells enhanced the generation of both classes of DTH effector cells, i.e., those that are Ly-1 positive and IA-subregion restricted and those that are Ly-2,3 positive and K,D-region restricted. The activity of the Th cells was found to be IA-subregion restricted and this was shown to operate at the level of the stimulator cells so that the delivery of help to the responder cells was not H-2 restricted. The possibility that the Th cells might be a precursor to the Ly-1 positive IA subregion-restricted DTH effector cells is discussed.

T cell regulation of polyclonal B cell responsiveness. III. Overt T helper and latent T suppressor activities from distinct subpopulations of unstimulated splenic T cells

Polyclonal activation of murine splenic B lymphocytes by lipopolysaccharide was found to be subject to regulation by helper and suppressor influences from T lymphocytes. In the normal adult spleen, only helper influences were exercised over polyclonal B cell activation; this influence is a property of Lyt-l(+)23(-) slowly sedimenting T cells. Suppressive influence evidently is latent, for it exists at such a low level (or the cells are so few in number) that its effects are difficult to detect. Suppressor T cell function may be evoked by culturing spleen cells at high ratios of T:B cells, by activating splenic T cells with concanavalin A, or by sonicating unstimulated splenic T cells to liberate a suppressive potential that is not expressed by these unstimulated cells when intact. The soluble fraction of resident splenic T cell sonicates exerts both helper and suppressor regulatory influences. The soluble helper activity is derived from Lyt-l(+)23(-) slowly sedimenting T cells, whereas suppressor activity is generated from a distinct subpopulation of Lyt-l(-)23(+) rapidly sedimenting T cells. The thymus contains cells capable only of helping but not of suppressing polyclonal activation of splenic B cells. Helper and suppressor activities contained in splenic T cell sonicates were separated by gel chromatography; the suppressive activity was found to elute with a molecular weight between 68,000 and 84,000 and the helper activity eluted with a molecular weight between 15,000 and 23,000. The data indicate that helper and suppressor activities are distinct molecular entities derived from distinct splenic T lymphocyte subpopulations. The possibility that these molecules are precursors to or components of antigen- specific or nonspecific helper and suppressor factors described in the literature is discussed.

Ia antigens on antigen-presenting cells do not carry the same Ia specificities as detected on suppressor and helper T cells

The passage of spleen cells through a tightly packed nylon wool column partially separated two populations of cells required for the antigen-induced secondary proliferative response of T cells. The proliferating T cells were in the nylon wool column-passed cell population, but the addition of a small number of nylon-wool-adherent cells was required for their maximal proliferative response. Such adherent cells were non-T, non-B, Ia antigen-positive cells serving as antigen-presenting cells. Ia determinants on this cell type are encoded in two separate I subregions, I-A and I-E/C, and they are expressed simultaneously on the same cells. Antisera specific for I-J subregion gene products having as a known activity the killing of antigen-specific suppressor and helper T cells were unable to kill antigen-presenting adherent cells. The results indicated that at least I-J subregion gene products expressed on suppressor and helper T cells are not present on antigen-presenting accessory cells. The Ia specificities detected on accessory cells follow the cross-reactive pattern found in Ia molecules of B cells, and thus antigen-presenting cells carry Ia antigen identical to those of B cells, and not those of T cells.

Flow cytometry and cytoadherence studies of sera from children with juvenile rheumatoid arthritis and normal controls

Recently, antibodies reactive with T cell subpopulations have been reported to exist in children with active juvenile arthritis (JRA). In an attempt to verify and extend these observations, we have studied children with JRA for the presence of anti-T cell antibodies by flow cytometry and cytoadherence rosette techniques. T cells were isolated from peripheral blood mononuclear cells (PBL) by two methods: 1) Differential sedimentation of PBL rosetted with neuraminidase-treated sheep erythrocytes, and 2) removal of immunoglobulin positive PBL by rosetting with rabbit anti-human F(ab')2 coated bovine erythrocytes and differential sedimentation. Utilizing these methods to detect lymphoreactivity of JRA sera to either population of T cell isolates, we observed the binding of ultracentrifuged normal human sera (NHS) to be comparable to JRA sera (active and quiescent). NHS reacted with 15-25% of T cells. Further studies demonstrate that monomeric IgG was chiefly responsible for lymphoreactivity. The results of these studies are discussed in the context of previous observations.

Mechanisms of regulation of cell-mediated immunity. VII. Suppressor T cells induced by suboptimal doses of antigen plus an I-J-specific allogeneic effect

Intravenous injection of 0.01 mM 2,4,6-trinitrobenzene sulfonic acid-derivatized syngeneic lymphoid cells generates a Thy-1-positive, antigen-specific suppressor cell for contact sensitivity which requires an I-J allogeneic effect to become fully activated. It is necessary and sufficient for all allogeneic effect to be directed solely against the suppressor cell, and once activated, the cell can suppress in an H-2-unrestricted fashion. The results are discussed in the framework of entry into the suppressor pathway, the allogeneic effect as a reflection of normal physiologic processes, and the importance of I-J as a receptor and signal among cells in the suppressor pathway.

Differences in the B cell interferon responses to lipopolysaccharide and poly I:C

Two polyclonal B cell activators, lipopolysaccharide (LPS) and poly I:C, have been used to induce interferon (IFN) production by murine B cell populations. The results show that splenic B cell-enriched fractions, isolated by wheat germ agglutination followed by C-dependent anti-Thy 1.2 cytolysis, respond to treatment with poly I:C + DEAE-dextran by IFN production at levels comparable on a per cell basis to unfractionated spleen cells. By contrast, the LPS-stimulated IFN response of these same B cell fractions is either undetectable or substantially lower than that of spleen cells; although the B cell fractions appear fully capable of LPS-induced proliferation. Consistent with this pattern of splenic B cell IFN responses, two antibody-secreting hybridoma lines and two myeloma cell lines (including the parental myeloma of the hybrid) can be stimulated by poly I:C + DEAE-dextran to produce IFN; yet these same B cell lines do not synthesize IFN in response to LPS at doses from 1-100 micrograms/ml. The level of poly I:C-induced IFN secreted by the hybridomas are approximately 10-fold greater than that produced by the unfused parental myeloma cells. Not only do these results directly demonstrate that murine lymphocytes of the B cell lineage produce IFN in response to the B cell activator poly I:C, but these observations also strongly suggest that the IFN responses of the B cell tumor lines model the IFN producing capacity of splenic B cells. Moreover, since the hybridoma cell lines and one of the myeloma lines synthesize specific antibody molecules, these observations show that the progeny of a single B cell clone can synthesize and secrete both IFN and immunoglobulin.

T cells in a suppressor circuit and non-T:non-B cells bear different I-J determinants

T cells involved in the generation of suppressor activity bear an I-J-subregion controlled determinant (e.g., J1) which is distinct from that (e.g., J2) found on non-T:non-B accessory cells. T-cell subsets examined include Ly-1 inducer and Ly-1,2 acceptor cells which collaborate to generate suppressor activity in the in vitro sheep red blood cell antibody system. Non-T:non-B accessory cells examined include accessory cells involved in concanavalin-A induced, T-cell proliferative responses and in in vitro antibody responses to sheep red blood cells. These results provide evidence for serologic and genetic complexity of the I-J subregion of the murine H-2 gene complex.

Autoregulation of immune responses via idiotype network interactions

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Ly-1 inducer and Ly-1,2 acceptor T cells in the feedback suppression circuit bear an I-J-subregion controlled determinant

An I-J-subregion controlled determinant is expressed on Ly-1 inducer and Ly-1,2 acceptor T cells in the feedback suppression circuit. Ly-1 T cells absorb the I-J antibody reactive with the Ly-1,2 acceptor T cell, suggesting that both inducer and acceptor T cells have the same I-J determinant. Since less than 10 percent of Ly-1 or Ly-1,2 T cells are killed by anti-I-J plus complement treatment, the I-J determinant demarcates functionally distinct subsets of both the Ly-1 and Ly-1,2 T-cell sets. This I-J determinant is not expressed on a detectable number of Ly-1 helper T cells which induce B lymphocytes to produce anti-sheep red cell antibody in tissue culture.

Intra-H-2 recombination in the mouse. III. I-Region characterization of haplotypes H-2at2, H-2at3 and H-2a2

Serological characterization of three K-S interval recombinant strains, TBR2 (H-2at2), TBR3 (H-2at3) and AIR 1 (H-2a2) was performed using anti-H-2, Ia, Ss and Slp antisera. The data presented here reveal that the crossover events in both TBR2 and TBR3 occurred between the I-A and I-E subregions. In both cases, the H-2K and I-A subregions were derived fron the H-2t1 of chromosome, while the I-E, S and H-2D regions were derived from the H-2b chromosome (KsAkEbSbDb). The H-2a2 chromosome resulted from a crossover event between the H-2a1 and H-2i9 chromosomes. Ia and Ss typing of AIR 1 suggested that the K to I-E regions originated from H-2a1 and the S and D regions originated from H-2i9 (KkAkEkSbDd).

Antigen-specific T-cell factors

Antigen-specific T-cell factors are mediator molecules which are produced by helper and suppressor T cells and which can perform the function of those cells in an antigen-specific manner. They probably play an important part in immunoregulation. The major histocompatibility complex has a controlling influence on their structure and activity, while their antigen-recognition properties may be conferred by immunoglobulin V regions. Interest in the factors derives from three related areas of research, namely (i) the problem of T-cell recognition of antigen; (ii) the mechanisms of cellular interactions in antibody production and cell-mediated immunity; and (iii) the genetic control of immune responses. This review discusses the literature up to June 1980 on their production, structure, genetic restriction and mechanism of action.

Antigen-specific helper T cells required for dominant production of an idiotype (THId) are not under immune response (Ir) gene control

Responder and nonresponder mice primed with poly-(L-glutamic acid,L-lysine,L-phenylalanine) (GLPhe), the response to which is under the control of immune response (Ir) genes, were used as a source of both types of helper T cells required for a T15 idiotype dominated T-dependent anti-phosphorylcholine (PC) response. It was found that the activity of one of the helper T cells needed for an anti-PC response was under major histocompatibility complex (MHC)-linked Ir gene control, and only GLPhe-primed responder mice could be used as a source of these cells. These T cells (ThMHC) whose presence is required for in vivo T-B collaboration are found in normal and anti-mu-treated mice, and their activity depends on the hapten being physically linked to the carrier molecule. By contrast, the activity of the second helper T cell (ThId) required for a T15-dominated anti-PC response was present in both GLPhe-primed responder and nonresponder mice. The ThId cell set that is missing or deficient in anti-mu treated mice can be restored by the addition of T cells from normal, carrier-primed donors and restimulating with the priming carrier. When T cells from GLPhe-primed donors are used as a source of ThId cells, both responder and nonresponder donors provide helper cells capable of inducing syngeneic B cells to produce a T15 dominated anti-Pc response. These results are interpreted to suggest that idiotype recognizing helper T cells (ThId) recognize antigen independent of known Ir gene products.

Murine T cell Ia antigens: specificity Iat.46 maps in I-J to I-E chromosomal segment of H-2 complex

An alloantiserum was prepared in C57BL/10 mice hyperimmunized with concanavalin A-stimulated B10.HTG thymocytes. Absorption with separated B10.A(3R)B and T lymphocytes, followed by titration on these cell types, revealed a new I-region controlled T-cell specificity, Iat.46. The determinant is present on a subpopulation of mature peripheral T cells but not on B lymphocytes, thymocytes, or bone marrow cells. It is also observed using (A.TH X B10.HTT)F1 anti-A.TL antiserum on B10.A(3R) T lymphocytes. The k and d haplotypes are fully crossreactive with regard to Iat.46 expression. B10.HTT, C57BL/10, and BSVS do not carry the Iat.46-encoding allele. Moreover, Iat.46 is not a determinant formed by I-A--I-E gene complementation. The Iat.46-controlling gene, Ia-8, may be positioned to the left of the B10.HTT crossover and to the right of the B10.A(3R) recombinational event. Thus, this determinant may be considered either to represent complexity within the I-J subregion or to demarcate a new I subregion between I-J and I-E.

The role of H-2-linked genes in helper T cell function. VII. Expression of I region and immune response genes by B cells in bystander help assays

The mode of action by bystander helper T cells was investigated by priming (responder X nonresponder) (B6A)F1 T cells with poly-L-(Tyr, Glu)-poly-D,L-Ala--poly-L-Lys [(TG)-A--L] and titrating the ability of these cells to stimulate an anti-sheep red blood cell (SRBC) response of parental B cells and macrophages in the presence of (TG)-A--L. Under limiting T cell conditions, and in the presence of (TG)-A--L, (TG)-A--L-responsive T cells were able to drive anti-SRBC responses of high-responder C57BL/10.SgSn (B10) B cells and macrophages (M0), but not of low-responder (B10.A) B cells and M0. Surprisingly, the (TG)-A--L-driven anti-SRBC response of B10.A B cells was not restored by addition of high-responder acessory cells, in the form of (B6A)F1 peritoneal or irradiated T cell-depleted spleen cells, or in the form of B10 nonirradiated T cell-depleted spleen cells. These results suggested that (TG)-A--L-specific Ir genes expressed by B cells controlled the ability of these cells to be induced to respond to SRBC by (TG)-A--L-responding T cells, implying that direct contact between the SRBC-binding B cell precursor and the (TG)-A--L-responsive helper T cells was required. Analogous results were obtained for keyhold limpet hemocyanin (KLH)-driven bystander help using KLH-primed F1 T cells restricted to interact with cells on only one of the parental haplotypes by maturing them in parental bone marrow chimeras. It was hypothesized that bystander help was mediated by nonspecific uptake of antigen [(TG)-A--L or KLH] by SRBC-specific b cells and subsequent display of the antigen on the B cell surface in association with Ir of I-region gene products, in a fashion similar to the M0, where it was then recognized by helper T cells. Such an explanation was supported by the observation that high concentrations of antigen were required to elicit bystander help. This hypothesis raises the possibility of B cell processing of antigen bound to its immunoglobulin receptor and subsequent presentation of antigen to helper T cells.

Analysis of histocompatibility requirements for proliferative and helper T cell activity. T cell populations depleted of alloreactive cells by negative selection

T cell populations were prepared from donors immunized with hapten-carrier conjugates and were depleted of alloreactive cells by negative selection. This was accomplished by injection of the cells into H-2-disparate irradiated recipients and recovery from the thoracic duct after 18-40 h. The genetic requirements for the proliferative and helper activity of these populations was determined. The proliferative response to antigen presented on adherent, Thy-1-negative cells was determined, and a requirement for syngeneic antigen-presenting cells (APC) was demonstrated. The same T cells were assayed for their ability to give help to hapten primed B cells. It was shown that there was a requirement for syngeneic APC and for linked recognition of hapten and carrier determinants on the same molecule by the B cell and T cell. There was no requirement for the B cell to be H-2 compatible with the T cell. The requirement for linked recognition was taken as evidence that the responses in allogeneic combinations were not a result of positive allogeneic effects. Precisely comparable restrictions were found with positively selected cells.

Quantitative studies on T cell diversity. I. Determination of the precursor frequencies for two types of streptococcus A-specific helper cells in nonimmune, polyclonally activated splenic T cells

A limiting-dilution system is described that makes use of T cell growth factor T cell expansion and allows the determination of precursor frequencies for various regulatory and effector T cells in nonimmune, polyclonally, or specifically activated T cell populations. Two different sets, a frequent and a rare set, of T helper cell precursors with specificity for trinitrophenyl-group A streptococcal vaccine, could be identified: the frequent set is of the Lyt-123 phenotype, and is present at frequencies of from 1/1,000 to 1/6,000 splenic T cells. It is only active at low cell numbers, whereas it is completely inactivated at greater cell numbers, presumably by suppressor T cells of lower frequency but greater potency. The rare set is of the Lyt-1 phenotype, is present at frequencies of from 1/10,000 to 1/70,000, and is not sensitive to suppressor cells present within the tested cell numbers. We suggest that the frequent set contains primiary helper cell precursors, whereas the rare set contains helper T memory cells preselected by previous exposure to other antigens. The results are discussed with respect to other reports on the involvement of more than one set of helper cells in antibody production.

Nature of the decline in antigen-induced humoral immunity with age

An attempt has been made to summarize our present knowledge of the influence of age on humoral immunity, as judged by the ability of an individual to generate antibody in response to antigenic stimulation. In general, humoral immunity declines with age, and the onset can occur as early as when an individual reaches sexual maturity. The decline is due to changes in the immune cells and their milieu. Cell loss, shift in the proportion of subpopulations, and qualitative cellular changes have all been detected. The most prominent cellular target of aging appears to be T cells involved in the regulation of humoral response. Since the changes are closely associated with the involution and atrophy of the thymus, an understanding of its changes could be the key to understanding immunosenescence.