Antigen-Specific T-cell factors in the immune response to poly(Tyr,Glu)-poly(Pro)-poly(Lys)

The production by T cells of an antigen-specific factor capable of replacing the T-cell function in specific antibody formation was used as a tool for studying the cellular aspects of the genetic control of immune responses. The ability of different T-cell populations to produce a cooperative signal and the ability of B-cell populations to react to this signal were studied in different mouse strains. The antigen used was the synthetic polypeptide poly(LTyr,LGlu)-poly-(LPro) —poly(lXys), (T,G)-Pro -L, the response to which was found not to beH-2-linked. It was found that the SWR strain of mice, a low responder to (T,G)-Pro -L, is not capable of producing a T-cell factor specific to this antigen, but its B cells react normally to an active factor produced in a high responder strain. In the DBA/1 strain, also a low responder to (T,G)-Pro -L, the bone marrow cells are not able to cooperate with an active T-cell factor to produce anti-(T,G)-Pro —L-specific antibodies, while their T cells do produce a (T,G)-Pro -L-specific factor. The SWR (low responder) B cells can be triggered by DBA/1 (low responder) T cells factor specific to (T,G)-Pro —L to produce an antibody response to this immunogen. These results suggest that the immune response to (T,G)-Pro -L is controlled by two genes which are expressed in different lymphocyte populations.     

Specificity of H-2-linked Ir gene control in mice: demonstration of T helper cells recognizing branched synthetic polypeptides in low responder mice

This report provides evidence for the presence of T helper cells capable of recognizing the polypeptide antigens T6-A--L and (H,G)-A--L in low responder mice of H-2k and H-2b haplotypes, respectively. Mice were primed in vivo with the T6-A--L-avidin-(H,G)-A--L complex or, in the case of T6-A--L in H-2k mice, with the cross-reactive and permissive antigen T6-S--L. T helper cells cooperating with DNP-primed B cells could be rechallenged in vitro with the DNP-conjugates of T6--A--L or (H,G)-A--L, although the cells were of low responder type with respect to these antigens. This implies that T cell-macrophage interaction required for restimulation is apparently not defective in these low responders. The implications of these results for the concept of Ir gene control are discussed.     

Clonal analysis of the primary and secondary B cell responses of neonatal, adult, and xid mice to (T,G)-A--L

The splenic focus assay was used to clone B cells from neonatal, adult and xid mice in order to examine their primary and secondary responses to (T,G)-A--L. Adult precursor cell frequencies to (T,G)-A--L were achieved late in neonatal ontogeny. Primary xid B cells responded to DNP-HY but not to (T,G)-A--L in the splenic focus assay. The frequency of secondary B cells from (T,G)-A--L-primed xid mice was less than or equal to 10% that of secondary B cells from wild-type (non-xid or X/Xxid heterozygous) mice. Although xid B cells were poorly responsive to (T,G)-A--L in the splenic focus assay, (T,G)-A--L-primed xid mice could provide help as recipients for stimulation of wild-type primary and secondary B cells. It seems likely that the B2 subset contributes most of the splenic focus response to (T,G)-A--L. The fine specificities of antibodies produced by neonatal, xid, and adult (wild-type) B cell clones were analyzed using analogues of (T,G)-A--L. A specificity shift was observed between the adult primary and secondary antibody responses to (T,G)-A--L. Less than 10% of adult primary clones produced antibodies cross-reactive on (Phe,G)-A--L (recognizing A--L determinants or Phe,Glu determinants), whereas more than 70% of primary clones produced Tyr,Glu side-chain specific antibodies cross-reactive on GT. The percentage of clones producing GT-binding antibodies diminished in the secondary response, while the percentage of clones producing antibodies cross-reacting on (Phe,G)-A--L increased. Neonatal clones also produced mostly GT-binding antibodies but gave a higher percentage of (Phe,G)-A--L-cross-reacting antibodies than adult primary clones. The specificities of secondary antibodies produced by xid and wild-type B cell clones were dissimilar. First, xid secondary clones were "primary-like" in that no anti-A--L antibodies were detected. Second, clones whose antibodies bound side-chain determinants but not GT were produced in higher frequency by xid than by wild-type secondary B cells. The differential responsiveness of B cell subsets to antigen and regulatory signals may influence memory B cell generation and the specificity of antibodies produced in the primary vs secondary response.     

An IL 2-secreting T cell hybridoma that responds to a self class I histocompatibility antigen in the H-2D region

A self-reactive T cell hybridoma that secretes IL-2 in response to H-2d haplotype cells resulted from a fusion of BALB/cBy lymph node cells with the AKR thymoma BW5147. The lymph node cells used had been enriched for cells reactive to (TG)-A--L, but neither this antigen nor fetal calf serum were required for stimulation of the hybridoma designated 3DT52.5. The gene product responsible for stimulation mapped to the H-2D region. Allogeneic cells of the b, f, k, q, and s haplotypes failed to stimulate. Not all H-2d haplotype cells were effective stimulators of 3DT52.5. Peritoneal cells and splenic B cells were much more stimulatory than splenic T cells. Most tumor cell lines of H-2d derivation and of B cell or macrophage/monocyte lineage were stimulatory, whereas H-2d T cell lines were not. The capacity to stimulate 3DT52.5 did not correlate with the ability to stimulate I region-restricted hybridomas, or with the ability to be induced to stimulate such hybridomas. Stimulatory cell lines did not apparently produce a soluble factor required for stimulation, and negative cell lines were not inhibitory. The monoclonal antibody 27-11-13, which reacts with H-2D of the b, d, and q haplotypes, inhibited stimulation of 3DT52.5 but did not inhibit stimulation of the sibling hybridoma 3DT18.11, which responds to (TG)-A--L plus I-Ad. Conversely, the monoclonal anti-I-Ad antibody MK-D6 inhibited stimulation of 3DT18.11 but not 3DT52.5. Although it is clear that 3DT52.5 recognizes a class I antigen coded for in the H-2D region, the precise molecular nature of the antigen is unknown. The structure of the antigen receptor on this hybridoma may prove to be of interest when it can be compared with receptors found on T cell hybridomas restricted by class II histocompatibility antigens.     

Antigen-specific T cell factors: a fine analysis of specificity.

The specificity of T cell factors produced in presence of synthetic polypeptide antigens was studied. Factors prepared with either one of the three antigens: poly(Tyr,Glu)-poly(DLALa)--poly(Lys), (T,G)-A--L, poly(Phe,Glu)-poly(DLALa)--poly(Lys), (Phe,G)-A--L, and poly(His,Glu)-poly(DLALa)--poly(Lys), (H,G)-A--L, successfully cooperated with B cells for antibody production to the homologous as well as to the other two immunogens. Furthermore, the activity of a (T,G)-A--L-specific factor was removed after passage through immunoadsorbents built of Sepharose coupled to: (T,G)A--L, (Phe-G)-A--L and poly(Glu)-poly(DLAa)--poly(Lys), (G)-A--L, but not to poly (DLALa)--poly(LLys),A--L. No cross-reactivity was observed between (T,G)-A--L and poly(Tyr,Glu)-poly(Pro)--poly(Lys), (T,G)-Pro--L, at the level of T cell factors, as shown using the above approaches. These results lead to the conclusion that specificity of T cell factors, although not identical, is similar to that of antibodies.     

Major histocompatibility complex-restricted augmenting T cells induced by in vitro cultivation of antigen-primed T cells. A new parallelism between suppressor and augmenting circuits

In vitro cultivation of primed T cells with antigen resulted in the induction of a regulatory T cell that nonspecifically augmented the in vitro antibody responses of H-2-compatible T and B cells. This T cell, designated as the augmenting T cell (Ta), was unable to help B cells by itself but enhanced the antibody response of B cells to several multitudes only when conventional helper T (Th) cells or cloned Th cells from the same H-2 haplotype coexisted. Ta was radioresistant and belonged to Lyt-1+, 2-, L3T4+, I-J- T cell lineage. Ta exhibited interesting H-2-restricted activities: when primed T cells from (A X B) F1 were cultured with the antigen in the presence of parent A type antigen-presenting cells, the induced Ta was able to augment the antibody response of (A x B) F1 B cells in the presence of Th cells from F1----A but not from F1----B radiation bone marrow chimeras. This indicates that the induction of Ta in an F1 T cell population is dependent on the H-2 haplotype of antigen-presenting cells during in vitro cultivation. The restriction specificity of the established Ta is, however, not directed to the class II antigen itself but to the restriction specificity of Th cells that recognize class II antigen. In support of this is the fact that the elimination of A-restricted Th cells during cultivation by treatment with anti-I-J mAb, which is known to react with H-2-restricted Th cells, resulted in failure of induction of Ta cells having the augmenting activity for the A-restricted response.     

Xid and normal mice express a light chain-associated cross-reactive idiotype in response to (T,G)-A--L and (T,G)-A--L-mBSA

Rabbit anti-idiotypic (Id) antibodies were prepared against purified ascites anti-(T,G)-A--L antibodies (TGB5) that had been absorbed to remove A--L-specific antibodies and were specific for (T,G)-side chain determinants. Purified rabbit anti-TGB5 Id antibodies detected an allotype-independent, light chain-associated cross-reactive Id expressed by the majority of individual mice immunized with (T,G)-A--L, (T,G)-A--L coupled to methylated bovine serum albumin (mBSA), or the linear terpolymer GAT. Primary and secondary monoclonal hybridoma protein (HP) antibodies from X/Xxid heterozygous (wild-type) mice immunized with (T,G)-A--L and/or (T,G)-A--L-mBSA were analyzed for isotypy and were grouped into eight antibody fine specificity sets defined by the patterns of direct binding to the antigens (T,G)-A--L, (Phe,G)-A--L, (T,G)-Pro--L, GT, and A--L. Analysis of these primary and secondary HP for TGB5 idiotypy showed a preferential expression of the TGB5 Id among GT+-binding HP (antibody fine specificity sets 1 through 3). All of the primary GT+-binding HP and the majority of secondary GT+-binding HP (sets 1 through 3) were TGB5 Id+. Most but not all of the TGB5 Id+ HP bound GAT. Of the side-chain-specific HP (sets 1 through 7), 78% of primary HP vs 49% of secondary HP bound GT. By these criteria, the primary HP response appears more restricted than the secondary HP response, consistent with the idea that Id diversification and antibody heterogeneity are regulated and selected events occurring during memory B cell generation. Although xid mice produce less antibody than wild-type mice to (T,G)-A--L, the TGB5 Id was produced early in the primary response by both xid and wild-type mice immunized with (T,G)-A--L or (T,G)-A--L-mBSA, and was maintained as a detectable Id in equivalent amounts in their secondary serum antibody responses. These results support the idea that distinct B cell subsets, including the xid B cell subset, share the same immunoglobulin gene repertoire.     

Functional requirements of (Phe,G)-A--L-specific T-cell clones of (H-2 b x H-2 kF1 origin

T-cell clones specific for the synthetic polypeptide antigen poly(LPhe, LGlu)-poly(DLAla)--poly(LLys) of (C57BL/6 x C3H/HeJ)F₁ origin were tested for their biological activities. One group of clones was restricted in its proliferative response to the H-2 ^b haplotype, the second to the H-2 ^k haplotype, and the third to the F₁ unique Ia determinants. All the clones which proliferated in response to antigen secreted interleukin-2 (IL-2) following stimulation. The H-2 restriction of the IL-2 secretion was the same as that of the proliferation. Two of the clones tested, C.6 and C.10, could provide help to B cells in antibody production. However, the genetic restriction profile of the helper activity was less stringent than that for the proliferative response. Thus, C.6, which proliferated in the presence of F₁ antigen-presenting cells only, could help B cells and accessory cells of C3H/HeJ. C.10, which was restricted in its proliferative response to the H-2 ^b haplotype, could collaborate with B cells and accessory cells of the H-2 ^k haplotype as well. The antibody response of both clones was restricted to the parental or F₁ strains.Abbreviations used in this paper (T, G)-A-L poly-(LTyr, LGlu)poly(DLAla)--poly(LLys) - (Phe, G)-A--L poly(LPhe, LGlu)-poly(DLAla)--poly(LLys) - APC antigen-presenting cells - Con A concanavalin A - FCS fetal calf serum - IL-2 interleukin-2     

Human helper-T-cell function does not require T4 antigen expression

The relationship between immunoregulatory T-cell function and the expression of T-cell subset-specific differentiation antigens was examined using a phenotypically anomalous human T-cell line (TCL), termed H-1. H-1 cells were found to express T11, extremely high levels of T3, but no T4 nor T8 antigen. Despite their lack of T4 antigen expression, H-1 cells could be activated by coculture with pokeweed mitogen (PWM), anti-T3 antibody, or autologous B cells to provide potent help for B-cell differentiation into plaque-forming cells (PFC). In contrast, H-1 cells did not suppress the PFC response triggered by PWM-activated T4+ cells. These results demonstrate that the expression of the T-cell subclass-specific differentiation antigen, T4, is not required for a T cell to become activated and to implement the program for helper function. In addition, enhanced expression of T3 on the T4-, T8-, H-1 cell surface may reflect a compensatory upregulation of the T3/Ti receptor complex on T cells which are deficient in these nonpolymorphic associative recognition structures.     

Anti-idiotype stimulation of antigen-specific antigen-independent antibody responses in vitro. II. Triggering of B lymphocytes by idiotype plus anti-idiotype in the absence of T lymphocytes

Antibodies specific for the idiotypes of B10 anti-(T,G)-A--L antibodies (anti-id) induced B lymphocytes to secrete anti-(T,G)-A--L antibodies in vitro in the absence of both antigen and T lymphocytes, provided either that the B lymphocytes were previously primed in vivo with (T,G)-A--L or that id specific for (T,G)-A--L was added to the cultures. These antigen- and T lymphocyte-independent responses were antigen specific and appeared not to require accessory cells. The results suggested that B lymphocyte activation occurred via the formation of id-anti-id complexes, and evidence was obtained that this activation involved two separate interactions between the B lymphocytes and the id-anti-id complexes. These studies document a previously undescribed regulatory function of anti-idiotype antibodies.     

Fine specificity of antibodies to the synthetic polypeptide poly(L-tyrosine, L-glutamic acid)-poly(DL-alanine)--poly(L-lysine) and its ordered analogs as followed by solid-phase radioimmunoassay

The fine specificity of antibodies against (T,G)-A--L and its ordered analogs (T-T-G-G)-A--L and (T-G-T-G)-A--L was studied. Fifty percent of the antibodies against (T,G)-A--L are directed toward the T-T-G-G determinants and 19% against T-G-T-G-like determinants. The rest of the antibody response to (T,G)-A--L is directed against determinants which exist in (T,G)-A--L but are not cross-reactive with either T-T-G-G- or T-G-T-G-like determinants. Although (T-T-G-G)-A--L and (T-G-T-G)-A--L differ only in the sequence of tyrosine and glutamic acid in their side chains, no crossreactivity was observed between antibodies toward the two ordered polypeptide antigens.     

Production of antisera specific for idiotype(s) of murine anti-(T,G)-A--L antibodies.

Antibodies to the synthetic polypeptide (T,G)-A--L were raised in C57BL/10 and C3H.SW mice. For each strain, the anti-(T,G)-A--L antibodies from 10 animals were pooled, affinity purified on a (T,G)-A--L-Sepharose column, and used to immunize Lewis rats. The resulting rat antisera were adsorbed with insolubilized normal mouse globulin in order to remove anti-isotypic and anti-allotypic antibodies. The residual antibodies specifically inhibited the binding of (T,G)-A--L by anti-(T,G)-A--L as measured by a radioimmunoassay. The specificity of this inhibition was demonstrated as follows: 1) failure of the anti-(T,G)-A--L anti-idiotype to inhibit the binding of nuclease to anti-nuclease antibody of the same allotype; 2) failure of Lewis anti-[B10 anti-(T,G)-A--L] to inhibit C3H.SW anti-(T,G)-A--L and vice versa; 3) ability to absorb anti-C3H.SW anti-idiotypic activity on insolubilized C3H.SW anti-(T,G)-A--L but not on B10 anti-(T,G)-A--L. The same or cross-reactive idiotype(s) was present in the majority of individuals of each of these strains.     

Idiotypic analysis of hybridoma antibodies to branched synthetic polymer (Tyr, Glu)-Ala-Lys: idiotypic relationship with antibodies to linear random polymer (Glu60, Ala30, Tyr10)

The expression of three anti-GAT idiotypes, CGAT, Gte, and GA-1, on 17 C57BL/10 and four C3H.SW hybridoma anti-(T,G)-A--L antibodies was analyzed. These hybridoma anti-(T,G)-A--L antibodies exhibited two patterns of fine antigen binding specificity. The majority of the hybridoma antibodies bound the (T,G)-A--L, GT, and GAT polymers but not the GA polymer, and were designated as GT-reactive hybridoma antibodies. A minor population of hybridoma anti(T,G)-A--L antibodies bound to (T,G)-A--L but not to GT, GAT, or GA, i.e., (T,G)-A--L-specific. A complete correlation between fine antigen binding pattern and the expression of CGAT idiotype was demonstrated. None of the 21 hybridoma anti-(T,G)-A--L antibodies expressed the GA-1 idiotype. All of the GT-reactive and none of the GT-nonreactive hybridoma anti-(%,G)-A--L antibodies expressed the CGAT idiotype. Furthermore, the Gte idiotype was found on the majority of CGAT+-bearing C57BL/10 hybridoma anti-(T,G)-A--L antibodies. These results indicate that C57BL/10 anti-(T,G)-A--L antibody repertoire can be grouped into a minimum of three families; i.e., CGAT+ Gte+, CGAT+ Gte-, and CGAT- Gte- families, with the CGAT+ Gte+ family as the major compartment. This is confirmed by the high percentage idiotype binding of serum anti-(T,G)-A--L antibodies with anti-CGAT idiotypic antisera. Finally, anti-idiotypic antisera made against CGAT+ hybridoma anti-GAT or anti-(T,G)-A--L antibodies crossreact extensively with other CGAT+ hybridoma anti-GAT and anti-(T,G)-A--L antibodies. However, additional experiments demonstrated that CGAT+ hybridoma anti-(T,G)-A--L antibodies also possess private idiotypes.     

Inheritance in the rat of the antibody response to two different determinants of (T,G)-A--L

Two (T,G)-A-L preparations differing in molecular weight were tested for immunogenecity in two inbred rat strains, AS and BN. Both strains produced antibody with specificity towards different antigenic determinants on the (T,G)-A--L molecule. The inheritance of antibody response toward one of the determinants was autosomal, dominant and linked to the major histocompatibility complex. Although the antibody response toward the other determinant was also inherited as an autosomal dominant trait, it was not linked to the major histocompatibility complex.     

Study on the possible factors influencing the expression of H-2 restriction specificity and Ir phenotype of antigen-specific proliferative T cells with various types of radiation chimeras

To better understand the factors described previously as influencing the manifestation of H-2 restriction specificity and Ir phenotype of T cells from radiation bone marrow chimeras, we also examined H-2 restriction specificity (Ir phenotype) of antigen (DNP-OVA, (T, G)-A-L, (H, G)-A-L)-specific proliferative T cells generated in various types of H-2 incompatible radiation chimeras prepared under our specific-pathogen-free (SPF) condition. The results indicated the following: (a) T cells generated in F1----parent bone marrow chimeras preferentially manifested host-type H-2 restriction specificity and Ir phenotype, regardless of the radiation dose (8.70 vs 11.59 Gy); (b) T cells recovered from twice-reconstituted F1----(PA----PB) chimeras manifested primary host (PB)-type Ir phenotype; (c) T cells which were recovered from (B10.Thy-1.1 X B10.BR.Thy-1.1)F1----parent (Thy-1.2) bone marrow chimeras and treated with anti-Thy-1.2 plus complement to deplete host-derived T cells still manifested preferentially the restriction specificity for host-type H-2; (d) PA-derived T cells which had differentiated in a fully allogeneic host (PB) environment of (PA + PB)----PB chimeras manifested fully allogeneic host-type Ir phenotype; (e) T cells from F1----parent chimeras that were prepared with 13-day fetal liver cells also manifested host H-2-restricted Ir phenotype; and (f) host preference for Ir phenotype of antigen-specific proliferative T cells was observed even in the case of F1----parent bone marrow chimeras reconstituted with "intact" bone marrow cells. The data suggest that thymic APCs, surviving host T cells or the source of stem cells (adult bone marrow vs 13-day fetal liver), do not necessarily play a significant role in the manifestation of H-2 restriction specificity and Ir phenotype of T cells generated in H-2 incompatible radiation chimeras.     

Role of dendritic cells in the immune response induced by mouse mammary tumor virus superantigen.

After mouse mammary tumor virus (MMTV) infection, B lymphocytes present a superantigen (Sag) and receive help from the unlimited number of CD4(+) T cells expressing Sag-specific T-cell receptor Vbeta elements. The infected B cells divide and differentiate, similarly to what occurs in classical B-cell responses. The amplification of Sag-reactive T cells can be considered a primary immune response. Since B cells are usually not efficient in the activation of naive T cells, we addressed the question of whether professional antigen-presenting cells such as dendritic cells (DCs) are responsible for T-cell priming. We show here, using MMTV(SIM), a viral isolate which requires major histocompatibility complex class II I-E expression to induce a strong Sag response in vivo, that transgenic mice expressing I-E exclusively on DCs (I-EalphaDC tg) reveal a strong Sag response. This Sag response was dependent on the presence of B cells, as indicated by the absence of stimulation in I-EalphaDC tg mice lacking B cells (I-EalphaDC tg muMT(-/-)), even if these B cells lack I-E expression. Furthermore, the involvement of either residual transgene expression by B cells or transfer of I-E from DCs to B cells was excluded by the use of mixed bone marrow chimeras. Our results indicate that after priming by DCs in the context of I-E, the MMTV(SIM) Sag can be recognized on the surface of B cells in the context of I-A. The most likely physiological relevance of the lowering of the antigen threshold required for T-cell/B-cell collaboration after DC priming is to allow B cells with a low affinity for antigen to receive T-cell help in a primary immune response.     

T lymphocyte-enriched murine peritoneal exudate cells. III. Inhibition of antigen-induced T lymphocyte Proliferation with anti-Ia antisera.

The recent development of a reliable murine T lymphocyte proliferation assay has facilitated the study of T lymphocyte function in vitro. In this paper, the effect of anti-histocompatibility antisera on the proliferative response was investigated. The continuous presence of anti-Ia antisera in the cultures was found to inhibit the responses to the antigens poly (Glu58 Lys38 Tyr4) [GLT], poly (Tyr, Glu) ploy D,L Ala-poly Lys [(T,G)-A--L], poly (Phe, Glu)-poly D,L Ala-poly Lys [(phi, G)-A--L], lactate dehydrogenase H4, staphylococcal nuclease, and the IgA myeloma protein, TEPC 15. The T lymphocyte proliferative responses to all of these antigens have previously been shown to be under the genetic control of major histocompatibility-linked immune response genes. The anti-Ia antisera were also capable of inhibiting proliferative responses to antigens such as PPD, to which all strains respond. In contrast, antisera directed solely against H-2K or H-2D antigens did not give significant inhibition. Anti-Ia antisera capable of reacting with antigens coded for by genetically defined subregions of the I locus were capable of completely inhibiting the proliferative response. In the two cases studied, GLT and (T,G)-A--L, an Ir gene controlling the T lymphocyte proliferative response to the antigen had been previously mapped to the same subregion as that which coded for the Ia antigens recognized by the blocking antisera. Finally, in F1 hybrids between responder and nonresponder strains, the anti-Ia antisera showed haplotype-specific inhibition. That is, anti-Ia antisera directed against the responder haplotype could completely block the antigen response controlled by Ir genes of that haplotype; anti-Ia antisera directed against Ia antigens of the nonresponder haplotype gave only partial or no inhibition. Since this selective inhibition was reciprocal depending on which antigen was used, it suggested that the mechanism of anti-Ia antisera inhibition was not cell killing or a nonspecific turning off of the cell but rather a blockade of antigen stimulation at the cell surface. Furthermore, the selective inhibition demonstrates a phenotypic linkage between Ir gene products and Ia antigens at the cell surface. These results, coupled with the known genetic linkage of Ir genes and the genes coding for Ia antigens, suggest that Ia antigens are determinants on Ir gene products.     

Genetic control of the immune response to (T,G)-A--L in C3H in equilibrium C57 tetraparental mice

When 15 C3H ? C57 tetraparental (allophenic) mice were analyzed for coat color, hemoglobin, and immunoglobulin allotype, all but two were shown to be chimeric. These 15 tetraparental mice were immunized with the synthetic polypeptide (T,G)-A--L, and the origin of the (T,G)-A--L-specific antibody produced was determined by using genetic markers (allotypes) on the immunoglobulin heavy chain constant region. Five tetraparental mice were high responders to (T,G)-A--L and had significant amounts of a (low responder) allotype antibody in their total serum. Three of these mice had significant amounts of anti-(T,G)-A--L antibody of the a (low responder) allotype. The antigen binding capacities of the a allotype fractions of these three were 4–5 times higher than the antigen binding capacities of immunized C3H (low responder) control mice. These results are compatible with the hypothesis that the inability of low-responder mice to produce significant amounts of anti-(T,G)-A--L antibody is a function of Ir-1A gene expression at the level of T cells.     

Characterization of subtype-specific and cross-reactive helper-T-cell clones recognizing influenza virus hemagglutinin

The specificity and function of two T-cell clones derived from A/Memphis/1/71 (H3) influenza virus (Mem 71)-immune BALB/c spleen cells have been compared. One clone, X-31 clone 1, was subtype specific, proliferating in response to influenza strains of the H3 subtype only. The other, Jap clone 3, cross-reacted in proliferation assays with heterologous subtypes of influenza A, but not type B. Both clones recognized the HA1 chain of the hemagglutinin (HA) molecule and their proliferation in response to detergent-disrupted virus could be specifically inhibited by monoclonal antibodies to the HA. The T-cell clones were of the L3T4+ phenotype. Both recognized antigen in association with I-Ed, as indicated by studies with H-2 recombinant strains of mice and by blocking with monoclonal anti-I-E antibody. In vivo, both clones elicited a delayed-type hypersensitivity (DTH) reaction when inoculated into mouse footpads together with virus, X-31 clone 1 again displaying subtype specificity and Jap clone 3 being cross-reactive. The clones were also able to provide factor-mediated help in vitro to virus-primed B cells in an anti-HA antibody response. The cross-reactive T-cell clone provided help not only for B cells primed with influenza A subtype H3 and responding to H3 virus in culture, but also for H2 virus-primed B cells making anti-H2 antibody.     

Properties of antigen-specific suppressive T cell factor in the regulation of antibody response of the mouse. II.In vitro activity and evidence for the I region gene product.

An antigen-specific suppressive T cell factor, which was extracted from carrier-primed T cells, was further characterized in an in vitro secondary antibody response. The factor was capable of suppressing secondary IgG antibody response of primed spleen cells when it was added to the culture together with relevant antigen. The suppressive T cell factor was not released from primed T cells by a short-term culture with antigen, but was kept bound to the membrane of the residual cultured cells, only the physical disruption of which can release the T cell factor. The target of the suppressive T cell factor was determined as being the helper T cell, since the factor did not exert any effect in the absence of the helper T cell with identical specificity to that of the factor. The suppressive activity was completely absorbed with alloantisera specific for products of the I region of H-2 complex, although various anti-immunoglobulin antisera failed to do so. Close analysis of the specificity of alloantisera capable of absorbing the suppressor molecule indicated that the suppressive T cell factor may, in fact, be an I region gene product probably coded for by genes in I-A and/or I-B (including I-E) subregions.