Gain/loss of poly(Glu50Tyr50)/poly(Glu60Ala30Tyr10) responsiveness in the bm12 mutant strain

Experimental autoimmune encephalomyelitis induced in B6.C-H-2bm12 mice by myelin oligodendrocyte glycoprotein: effect of MHC class II mutation on immunodominant epitope selection and fine epitope specificity of encephalitogenic T cells

The effect of the bm12 mutation on susceptibility to MOG-induced EAE, TCR repertoire and fine epitope specificity of the encephalitogenic T-cells, was assessed. prMOG35-55 was encephalitogenic for H-2bm12 and H-2b mice. Despite only minor differences in TCRVbeta expression and fine epitope specificity, H-2bm12/ and H-2b/prMOG35-55-specific T-cells failed to recognize Ab/prMOG35-55 and Abm12/prMOG35-55, respectively. rhMOG-induced EAE was milder in H-2bm12 mice, possibly as a result of co-dominant responses to prMOG35-55 and to the non-encephalitogenic pMOG94-116, rather than a single dominant response to prMOG35-55 in H-2b mice.

Horse gammaglobulin-induced thrombocytopenia in anaphylaxis involving sequestration and activation of platelets

Thrombocytopenia as well as hemoconcentration and leukopenia followed by leukocytosis were induced after HoGG challenge on HoGG-sensitized mice. Thrombocytopenia was induced within 2 min and sustained for 1 day. HoGG-induced thrombocytopenia was not observed until day 10 after sensitization; mice challenged with HoGG dose > or = 10 micrograms developed thrombocytopenia. Two types of thrombocytopenia were observed in appropriately sensitized mice. HoGG induced thrombocytopenia at 2 min and 60 min, whereas, alpha-macroglobulin induced thrombocytopenia at 2 min, the platelet count of which returned to normal within 60 min. Poly (Glu60Ala30Tyr10) did not induce thrombocytopenia at 2 min or 60 min. The tracing study by 3H-serotonin labelled platelets demonstrated the 2 min-sequestration of platelets in lungs or livers. The HoGG-induced sequestration of platelets at 2 min was blocked by high dose heparin or Cobra Venom factor. Platelet activation at 60 min was partially inhibited by dexamethasone, rhodostomin synthetic peptide 45-59, or platelet activation factor antagonist (WEB 2086). Furthermore, the thrombocytopenia could be transferred by heat (56 degrees C, 4h) treated immune sera. This suggests that HoGG-induced, non-IgE-mediated thrombocytopenia in anaphylaxis involves sequestration and activation of platelets. The sequestion in lungs occurs within 2 min and can be inhibited by high dose heparin or Cobra Venom factor. The activation of platelets involves platelet activation factor, and fibrinogen receptor.

Involvement of histamine or tumor necrosis factor in early-type hypersensitivity

A novel early-type hypersensitivity (ETH) reaction, manifested as capillary congestion, increase of vasopermeability, and plasma protein leakage, can be induced within 1 h after challenge of antigen-sensitized mice. The mediators involved in ETH varied among different strains of mice. The poly(Glu60Ala30Tyr10) (GAT)-induced ETH in BALB/c mice was blocked by diphenhydramine (histamine H1 antagonist) and ketanserine (serotonin antagonist), but not by cimetidine (histamine H2 antagonist). These results indicate that both histamine and serotonin are involved, and that the histamine effect is mediated through a H1 receptor. Meanwhile, GAT-induced ETH in B6 mice was inhibited by anti-TNF alpha antibody suggesting that TNF alpha is involved. The mice can be classified into either histamine or TNF alpha type based on the pattern of mediator involved in ETH. A/J and CBA strains as well as BALB/c mice were classified as histamine type while A. TL, B10.BR, and C3H/He in addition to B6 mice were TNF alpha type. The observation that GAT-induced ETH in (BALB/c x B6)F1 mice was inhibited by both diphenhydramine and anti-TNF alpha suggests that the mediation of the actions of histamine or TNF alpha by GAT was genetically controlled and inherited as the dominant trait in (BALB/c x B6)F1 mice. ETH could be passively transferred by heat (56 degrees C, 4 h)-treated anti-GAT sera. Sera derived from the histamine type transferred ETH across the type barrier and histamine was the mediator, irrespective of the type of the recipient. However, sera derived from TNF alpha type only transferred ETH to the mice of the same TNF alpha type and TNF alpha was the mediator.

Alteration of copolymer-specific humoral and cell-mediated immune responses by ethanol

Excessive alcohol consumption represents a major human health threat. The frequency and severity of infections in alcoholics is often pronounced, suggesting impaired immune function in these patients. The precise effect of ethanol on cells of the immune system is poorly understood. We have previously shown that synthetic copolymers of L-amino acids, GT and GAT, are powerful tools for clarifying the role of regulatory T-cells in both cell-mediated and humoral immunity in inbred mouse strains. We asked whether these same antigens would have application to a murine model of ethanol consumption. In this study, female mice were placed on a nutritionally complete liquid diet containing 35% ethanol-derived calories. As control, mice either were placed on a liquid control diet that isocalorically substitutes sucrose for ethanol or remained on a solid diet consisting of standard laboratory chow and water ad libitum. Our data show that the liquid ethanol diet severely inhibits two measures of cell-mediated immunity, the ability of responder B6 mice to make an anti-GAT delayed hypersensitivity and GAT-specific T-cell proliferative responses as compared with pair-fed liquid control diet or solid diet controls. On the contrary, this liquid ethanol diet does not significantly impair humoral immunity; it allows nonresponder C57BL/6 or C3H/HeN mice to respond in vivo to GT immunization. These findings suggested to us that the effect of ethanol may occur prior to antigenic stimulation, and this was confirmed by in vitro immunization.

Hepatitis B surface antigen induces an early-type hypersensitivity

In addition to the delayed-type hypersensitivity (DTH), a unique type of hypersensitivity could be induced at a late stage of the immune responses after hepatitis B surface antigen (HBsAg) immunization. This antigen-specific ear swelling that develops within 1 h after antigen challenge has been referred to as the early-type hypersensitivity (ETH) in contrast to the 24-h DTH. Although expression of ETH was earlier than DTH, the induction of the former needed 3 days longer than that of the latter. In ETH, the plasma protein leaked into the tissue and the vasopermeability increased within 15 min, causing the oedema of ETH. The observation that cyproheptadine, not dexamethasone, inhibited ETH suggests that it is mediated through the release of histamine and/or serotonin. Furthermore, ETH could be transferred by immune sera. Heat treatment (56 C for 4 h) did not destroy the transfer, suggesting that it was not mediated by IgE. The human anti-HBs sera from either hepatitis B virus infection or HBsAg vaccinee also contained the activity to transfer the ETH in mice.

Distinct regulation of humoral and cellular immunities to hepatitis B surface antigen

The surface envelope protein of hepatitis B virus (HBsAg) stimulates the immune system to produce anti-HBs antibodies and to generate cell-mediated immunity. These two arms of immunity were found to be regulated differently in bm12 (H-2bm12) or CBA and C3H (H-2k) mice. In bm12 mutant (I-A beta mutant of B6 mice) mice, the anti-HBs production, early-type, and immune complex-type hypersensitivity were impaired, but the delayed-type hypersensitivity and the T-cell proliferation in vitro were normal compared to the parental B6 (H-2b) mice. The mutation of the A beta molecule seems to affect the immune responses differentially. On the other hand, C3H or CBA mice produced anti-HBs antibodies after major S protein (pre-S-depleted HBsAg) stimulation, but could not generate the hypersensitivity responses. The pre-S region could circumvent the non-responsiveness of the hypersensitivity response in C3H and CBA mice. These data suggest that the humoral and cellular immunities to the HBsAg particle are regulated distinctly and are affected by either the A beta molecule of the host or the pre-S region of the HBsAg.

Cell-mediated immune responses to poliovirus II. Survey of delayed hypersensitivity and T-cell proliferative responses in inbred mouse strains

Some epidemiological reports suggest a human genetic predisposition for susceptibility to the development of paralytic poliomyelitis. In a previous study of cell-mediated immune responses by mice to poliovirus (PV), we showed differences in the responses by BALB/c and C57BL/6 (B6) mice. The present study is a further analysis of the delayed hypersensitivity (DTH) and T cell proliferative (Tprlf) responses to PV in 17 different inbred strains of mice, to determine if these responses were under major histocompatibility complex (MHC) or other genetic control. Both DTH and Tprlf to PV did not correlate with MHC for responses to any of the three PV serotypes. Further, we found a lack of concordance of DTH and Tprlf responses to a given PV serotype. The cell-mediated immune responses by any one mouse strain to one PV serotype is not predictive of that mouse strain's response to another PV serotype.

Igh allotype-linked control of immune complex-type hypersensitivity induced by hepatitis B surface antigen

Hepatitis B surface antigen (HBsAg) induced an immune complex-type hypersensitivity which developed at 5-6 hr after the challenge and could be transferred by anti-HBs antisera, in addition to the delayed-type hypersensitivity in B10.BR mice. The pre-S region of HBsAg influenced this induction because the pre-S-depleted HBsAg or recombinant major S protein could not stimulate this 5-hr ear swelling. The male B10.BR mice responded better than the female ones, probably due to the inhibition by female hormone. Furthermore, HBsAg could also induce an early-occurring hypersensitivity which appeared within 1 hr of the antigen challenge. However, B10.BR mice did not exhibit this hypersensitivity; B6 mice expressed all three types of hypersensitivity (1 hr, 5 hr and 24 hr) and BALB/c mice showed only 1-hr and 24-hr responses. The expression of the immune complex-type seems to be determined by the Ighb gene or gene(s) closely associated to it. Mice bearing the Igh-1b allotype could be stimulated by HBsAg to induce the immune-complex type hypersensitivity. Moreover, it was the high specific binding not the titre of anti-HBs antibodies that influenced the exhibition of immune complex-type hypersensitivity.

Adoptive immunotherapy is suppressed in C57BL/6J and B6.C-H-2bm12 mice following recognition of congenic class II MHC antigen determinants

In previous reports, we have shown that adoptive transfer of tumor-sensitized T (immune) cells to tumor-bearing mice that have received a prior injection of cyclophosphamide (CY) results in the induction of permanent tumor regression in syngeneic strains. It has also been shown that adoptive immunotherapy results in an increased expression of class II MHC antigens (Ia) by macrophages at the tumor site and in the peritoneal cavity and is associated with expansion of CD4+ and CD8+ T cells at the site of tumor regression. In this report, we use the Ia mutant strain, B6.C-H-2bm12, and congenic C57BL/6J (B6) mice to determine the relative importance of Ia expression in regulating amplification of immune responses following adoptive immunotherapy and to test the hypothesis that recognition of congenic Ia determinants will result in the induction of suppressor mechanisms that down-regulate active immunity. The data indicated that the adoptive transfer of immune congenic T cells (B6 immune cells into CY-treated tumor-bearing bm12 mice and vice-versa) down-regulated active immunity, while the transfer of syngeneic immune cells resulted in permanent tumor regression. By using radiation-chimeric mice, it was shown that down-regulation was associated with incompatibility of the transferred immune T cells and bone-marrow-derived cells (putatively expressing the Ia haplotype of donor-derived macrophages) and the appearance of long-lived splenic suppressor cells. Suppression per se was shown to be induced in response to the Ia difference between the two strains and not in response to the MCA/76-9 sarcoma, which appears to be one of the few tumors that can induce active immunity in both the syngeneic and congenic strains without obvious subsequent down-regulation by suppression.

Characterization of three functional sites in alpha beta 1 DR of DRw13. All three sites are potentially involved in major histocompatibility complex-peptide interaction

An HLA-DR product encoded by the HLA-DRw13/Dw19 haplotype has been identified as the HLA class II molecule involved in antigen presentation to several influenza-specific helper T cell clones. Three different functional sites were identified on this molecule by comparing the structure of HLA-DR products of known sequences and their ability to efficiently present foreign antigen to the T cell clones. These functional sites were mapped on the recently proposed three-dimensional structure of HLA class II molecules. From their position, these sites are all potentially involved in HLA-peptide interaction and capable of affecting the binding and/or the conformation of the foreign peptide. This suggests that polymorphic residues essential in major histocompatibility complex restriction are mostly involved in peptide binding.

Murine MHC polymorphism and T cell specificities

The major histocompatibility complex (MHC) genes are polymorphic in mouse and man. The products of these genes are receptors for peptides, which while bound, are displayed to T lymphocytes. When bound peptides from antigens are recognized by T lymphocytes, an immune response is initiated against the antigens. This study assessed the relation of the polymorphic MHC molecules to their peptide specificity. The results indicate that although an individual of the species has a limited ability to recognize antigens, the species as a whole has broad reactivity. This rationalizes the extreme polymorphism observed.

Cell-mediated immune responses to poliovirus. I. Conditions for induction, characterization of effector cells, and cross-reactivity between serotypes for delayed hypersensitivity and T cell proliferative responses

Human polioviruses are categorized into three distinct serotypes (types 1, 2, and 3) based upon their reactivity with specific antibodies. Although a great deal of information has been amassed about the induction and characterization of poliovirus antibody responses, little is known about cell-mediated immunity to poliovirus and its role in protection. Here, we show that intracutaneous injection of ultraviolet light-inactivated poliovirus into the tailbase of BALB/c mice induces delayed hypersensitivity (DTH) and T-cell proliferative (Tprlf) responses. Both DTH and Tprlf responses to poliovirus are mediated by Ly-1high2-, L3T4-bearing T cells. Moreover, known serologic cross-reactivity (i.e., antibody-mediated) of poliovirus serotypes is not predictive of cross-reactivity between the cell-mediated immune responses.

DNA sequence analysis of I-Ak beta mutants reveals serologically immunodominant region

We have produced a series of in vitro serologically selected cell lines that express mutant I-Ak molecules. In this report we describe the DNA sequence analysis of the Ak beta gene of four cell lines that express serologically altered Ak beta polypeptides in association with wild-type Ak alpha polypeptides. Each of the major serologic epitopes on the Ak beta polypeptide has been altered in one or more of the four mutants. In addition, the four mutants exhibit a broad spectrum of functional defects when used to stimulate a panel of T hybridomas of various specificities. The DNA sequence analysis revealed that each mutant had sustained a single nucleotide substitution resulting in a single amino acid substitution. All four independent substitutions occurred within or near the third of the four variable regions defined in the beta 1 domain of the A beta polypeptide by allelic comparisons. These data strongly suggest that the third variable region is the major determinant of alloantigenicity on the Ak beta polypeptide.

Analysis of T-cell subset proliferation at afebrile and febrile temperatures: differential response of Lyt-1+23- lymphocytes to hyperthermia following mitogen and antigen stimulation and its functional consequence on development of cytotoxic lymphocytes

Poikilotherms are now known to increase their survival by behaviorally induced fevers in response to pathogenic infection. Increased host resistance to viral and bacterial infections has also been noted in homeotherms whose body temperature has been elevated by manipulation of ambient temperature. These observations suggest that fever may increase host resistance by augmenting acquired immunity; thus, this highly conserved response during evolution may provide a survival advantage against environmental pathogens. This possibility has prompted us to investigate the influence of a temperature characteristic of a modest fever in humans (39 degrees C) on T-cell proliferation and function. Our studies revealed that T-cell mitogenesis was enhanced when cultures were incubated at the febrile temperature (39 degrees C). Analysis of T-cell subsets demonstrated that temperature enhanced the mitogenic (Concanavalin A) response of Lyt-1+23- splenocytes; in contrast, hyperthermia was deleterious to lectin-driven proliferation of the Lyt-1-23+ population even in the presence of large quantities of recombinant interleukin-2 (rIL-2). B-cell mitogenesis was invariably inhibited by hyperthermia over a broad range of concentrations of lipopolysaccharide (LPS). Although T-cell mitogenesis was enhanced at the febrile temperature, T-cell proliferation induced by alloantigens or by a murine pathogen, Sendai virus (SV), was diminished at the febrile temperature. Hyperthermia inhibited SV-induced proliferation of Lyt-1+23- lymphocytes, indicating that a febrile temperature can either augment or inhibit T-cell proliferation of the same T-cell subset depending upon the activation signal (i.e., lectin or antigen). Because effector cell development depends upon antigen-induced clonal expansion (proliferation), we evaluated the influence of temperature on primary cytotoxic thymus (T)-derived lymphocyte (CTL) responses against alloantigens and secondary CTL responses against SV under afebrile and febrile conditions. We consistently observed that the induction of alloreactive and virus-specific CTL was diminished in cultures incubated at the elevated temperature, suggesting that a thermosensitive event(s) exists in the progression of CTL derived from either CTL precursors (CTLp) or memory CTL. Furthermore, hyperthermia reduced the number of SV-specific CTL detectable by limiting dilution analysis, suggesting that another event independent of clonal expansion was thermolabile during effector cell development. In view of these results, we suggest that it may be premature to conclude that the observed increase in host resistance induced by a febrile state is mediated by enhanced cell-me

Mechanisms of genetic control of immune responses. II. Nonresponsiveness in BALB/c GT-specific cell-mediated immune responses does not correlate with the absence of functional T cells or the induction of suppressor T cells

The mechanisms underlying Ir gene control of CMI were addressed by examining the DTH and Tprlf responses specific for the synthetic polymers GT, GAT, and GA. We show that BALB/c mice (GAT/GA responders, GT nonresponders) primed with GT fail to develop DTH and Tprlf responses specific for GT, GAT, or GA. GAT immunization resulted in DTH responses that could be elicited not only with GAT and GA but also with GT, demonstrating that GT-specific TDH are present in nonresponder mice. GT-specific DTH was transferred with Thy-1+ Lyt-1+2-, H-2 I-restricted, nylon wool nonadherent cells. GA-primed BALB/c mice developed GAT- and GA-, but not GT-specific DTH responses, indicating that GA and GT do not cross-react at the T-cell level. The ability of GAT [but not a mixture of GA plus GT, or GT electrostatically complexed to the immunogenic carrier MBSA (GT-MBSA)] to induce GT-specific DTH suggested a requirement for covalent linkage of stimulatory 'GA' and nonstimulatory 'GT' determinants present on the GAT molecule. Similarly, GT-specific in vitro Tprlf responses could be demonstrated in GAT-primed mice exhibiting significant levels of GT-specific DTH but not in GT- or GT-MBSA-primed mice. Tolerization experiments also suggested that GT-specific Th were involved in the development of GT-specific DTH in GAT-primed mice. The GT nonresponsiveness of BALB/c mice for DTH and Tprlf responses could not be reversed by treatments designed to abrogate Ts activity (priming with GT-MBSA and CY injection), nor could GT-primed cells be shown to inhibit the development or elicitation of GT-specific CMI in GAT-primed mice during the afferent and/or efferent stages of DTH. Our results suggest that GT nonresponsiveness does not result from the absence of GT-specific T cells or preferential induction of Ts. The results are discussed in the context of hole-in-the-repertoire and antigen presentation (determinant selection) models of Ir gene control.

Regulation of immune responses by I-J gene products. VI. Recognition of I-E molecules by I-J-bearing suppressor factors

Poly(Glu50Tyr50) (GT) is not immunogenic in most inbred mouse strains. GT injection produces an I-J--bearing, GT-specific T-cell--derived suppressor factor (GT-TsF1) in H-2b,d,k haplotype mice. GT-TsF1 generates second-order suppressor T cells (Ts2) in H-2a,d,k haplotype mice. Here, we show that in order for GT-TsF1 to act, the recipient strain must express I-E molecules. This suggests that T cells are not the primary target of GT-TsF1. GT-TsF1 can be presented by Ia+ A20-2J B lymphoma cells. GT-TsF1 presentation is blocked by anti-I-E, but not by anti--I-A, mAb, whereas GAT presentation is blocked by anti-I-A, but not by anti--I-E, mAbs. These data suggest that I-J recognizes (or is recognized by) I-E. The existence and role of I-J molecules in immune regulation are discussed in light of these data.

Epitope-specific regulation in Ir gene systems. I. Conditions for the induction of epitope-specific suppressors to poly(Glu60Ala30Tyr10)

Injection of responder mice with poly(Glu60Ala30Tyr10) (GAT) followed by immunization with GAT-methylated bovine serum albumin (GATMBSA) selectively suppresses anti-MBSA plaque-forming cell (PFC) and delayed hypersensitivity (DTH) reactions. Conversely, MBSA injection followed by GATMBSA immunization suppresses anti-GAT PFC and DTH, while anti-MBSA responses remain intact. Suppression occurs for doses of antigen which are optimally immunogenic. The suppression is specific and does not act in a bystander fashion. These results demonstrate that epitope-specific regulation is reciprocal, is not limited to humoral responses, and is not limited to molecules of low molecular weight.

H-2 class I mutants utilize novel restriction specificities in the trinitrophenyl-specific cytotoxic T-lymphocyte response

In antigen-specific cytotoxic T-lymphocyte (CTL) responses H-2 class I mutations usually result in a decreased recognition of the antigen in association with the mutant molecule by CTL from the strain of origin. However, the influence of class I mutations on the magnitude and specificity of CTL responses in the mutants has been studied in only a few instances, in which usually a partial or complete loss of responsiveness was found. We now report that class I mutants extensively use gained (novel) CTL restriction sites, generated by the mutations in the CTL response against the hapten trinitrophenyl (TNP), demonstrated both at the population level and in limiting dilution. TNP-specific CTL clones, restricted by mutant-specific determinants, were detected in all mutants. The percentages mutant-specific CTL clones in limiting dilution experiments were 43, 40, 35, and 13 in the Kb mutants bm1, bm8, bm3 and bm5, respectively, and 35 in the Db mutant bm 14. It is concluded that H-2 class I mutations led to changes in the TNP-specific CTL repertoire resulting in gain of CTLs uniquely restricted to the mutant molecule.

The murine bm12 gene conversion provides evidence that T cells recognize predominantly Ia conformation

The structure of the highly polymorphic Ia dimer is the genetically determined factor that controls the immune response to foreign antigens, albeit the mechanism remains unresolved. However, it is clear that, in diverse immune responses, effector T lymphocytes require recognition of self-Ia and foreign antigenic determinants on the surface of an antigen-presenting cell or an antibody-secreting B cell. Furthermore, a single Ia molecule has been found to possess several independently acting functional domains. In this report T-cell recognition of Ia was limited to a single, defined structure by using the Ia mutant mouse strain B6.C-H-2bm12 (bm12). The Ia determinant being recognized is the site of the mutation that represents a difference in three of five amino acid residues in a hypervariable region of its beta chain. This mutation has been proposed to have resulted from a gene conversion-like event and is known to have functional importance. Recognition of the bm12 mutation site was studied here in in vitro cultures of T cells generated against Iabm12 antigens. The specificity of these alloreactive T cells was tested by using stimulator cells expressing various Ia alloantigens of known structure. Our findings provide direct genetic evidence that T cells recognize predominantly conformational determinants on Ia molecules and not their primary structure. The implications of these findings on our understanding of the genetic control of the immune response and the potential to modulate these responses in an antigen-specific way are discussed.

Anticollagen antibodies and immune response gene products in rheumatoid arthritis

Circulating antibodies to native and denatured types I and II human and bovine collagens were assayed in patients with rheumatoid arthritis (RA), patients with other rheumatic diseases, and normal individuals. A subgroup of this population was also assayed for reactivity with typing reagents which detect determinants (MT and HLA-DR) present in human immune response gene products. The mean titers of antibodies to each collagen tested were not significantly higher in RA patients when compared with patients who had other rheumatic diseases. Although both MT3 and MT4 were significantly associated with RA, there was no significant association between the anticollagen antibodies and any MT type or HLA-DR4. These studies raise a question concerning the role of collagen antibodies in the pathogenesis of RA and suggest that genes distinct from those coding for HLA-DR may play a role in the expression of the disease.

Analysis of the (H-2b X H-2k)F1-restricted response to insulin. Ab alpha Ak beta hybrid Ia molecules restrict the response towards the glutamic acid A4 epitope

The aim of these studies was to characterize the (H-2b X H-2k)F1-unique restriction element(s) responsible for presentation of bovine insulin (BI) to a long-term cultured T-cell line (BK-BI-1.2). (B10.BR X bm12)F1 spleen cells, which express a normal Ab alpha Ak beta molecule but a mutated Ak alpha Abm12 beta product on their cell surface, were perfectly able to act as BI-presenting cells. Antibody inhibition experiments with antibodies directed at I-Ak products revealed that monoclonal antibody 10-2.16, which reacts with the Ak beta polypeptide chain, abrogated BI-directed T-cell proliferation, whereas antibody H116-32.R5 with specificity for the Ak alpha chain was not inhibitory. These results identified the Ab alpha Ak beta complex as restriction structure. Recognition of BI in the context of the Ab alpha Ak beta molecule depended on the glutamic acid residue in position 4 of the A chain of bovine insulin. Twenty to twenty-five percent of the secondary proliferative response of (B10 X B10.BR)F1 lymph node T cells primed with BI in vivo was directed at the A4 determinant, suggesting that BK-BI-1.2 T blasts are representative of T-cell clones with measurable frequency. In (B10.BR X bm12)F1 mice, which lack a functional Ab alpha Ab beta restriction element, up to 80% of the proliferative response was dependent on the A4 epitope.

Immunoregulatory pathways in adult responder mice. I. Induction of GAT-specific tolerance and suppressor T cells for cellular and humoral responses

This report describes the alteration of helper-suppressor balances in an immune response (Ir) gene-controlled system by varying the route and form of antigen injection. Adult responder BALB/c mice develop Lyt 1+2-, T cells for delayed-type hypersensitivity (DTH), and T-cell proliferative (Tprlf) responses to subcutaneous injection of either poly(Glu60Ala30Tyr10) (GAT)-coupled syngeneic spleen cells (GAT-SP) or GAT emulsified in complete Freund's adjuvant. In contrast, intravenous injection of adult responders with GAT-SP results in specific unresponsiveness for DTH, Tprlf, interleukin-2, and plaque-forming cell (PFC) responses. This tolerance is mediated by both suppressor T cells (Ts) and a functional clonal inhibition. Lyt 1-2+ Ts suppress the induction (afferent limb) of GAT-specific DTH and PFC but not Tprlf responses. The reduced T-cell proliferation observed in GAT-tolerant mice is due to a non-transferable mechanism(s), possibly functional clonal inhibition. Our data are compatible with a multi-step pathway involving both proliferating and non-proliferating helper T (Th) cells. In addition, the fine specificity of tolerance induction for DTH and Tprlf responses was examined by using the related antigens poly(Glu60Ala40) (GA) and poly(Glu50Tyr50) (GT). Tolerance is exquisitely specific, as GA tolerizes responses to GA and GAT, whereas GT tolerizes GAT but not GA responses. Thus, both the route and form of antigen administration are important to the induction and regulation of immune response in Ir gene-controlled systems. Possible mechanisms governing the Th/Ts balance and the induction of GAT-specific tolerance and suppression for cellular and humoral responses in adult responders are discussed.

Nucleotide sequence of mutant I-A beta bm12 gene is evidence for genetic exchange between mouse immune response genes

Immune response genes of the murine major histocompatibility complex encode cell-surface glycoproteins that are expressed predominantly on B cells and macrophages and regulate immune responsiveness by restricting antigen recognition by T cells. The two classes of immune response molecule, termed I-A and I-E, are each comprised of two polymorphic chains (alpha and beta), and nucleotide sequence analysis of genomic or cDNA clones has revealed that most of the amino acid differences between allelic I-A alpha or beta chains occur in the first extracellular domain. The mutant mouse strain B6.C-H-2bm12 (bm12), which differs from its parental strain C57BL/6 (B6) at the I-A beta locus, exhibits an immune response profile markedly different from that of B6. Here we present the nucleotide sequence of the mutant bm12 I-A beta gene. Sequence comparison within the coding regions reveals three productive nucleotide differences between the I-A beta genes of B6 and bm12 mice, all three differences occurring within a stretch of 14 nucleotides in the exon encoding the first extracellular domain. The clustered nature of the bm12 mutation, as well as the specific amino acid changes it engenders, suggest a possible mechanism for the generation of polymorphism in class II antigens.

Mechanisms of genetic control of immune responses. I. Evidence for distinct multi-step helper T-cell pathways in cellular and humoral responses to GAT

We examined multiple genetically regulated humoral and cell-mediated immune (CMI) responses to poly( glu60ala30tyr10 ) (GAT) using a panel of mouse strains. We show that assignment of responder/nonresponder status depends upon the assay method. In addition, two distinct categories of nonresponder mice were found: (1) those which are unresponsive by all parameters tested (H-2q and H-2s haplotypes) and (2) those which are partially nonresponsive [H-2bm12 mutant strain--a low/nonresponder by splenic plaque-forming cell (PFC) and delayed-type hypersensitivity (DTH) responses, but exhibits B6 parental levels of high GAT-specific T-cell proliferation ( Tprlf ) and interleukin-2 production]. The distinction between these two nonresponder types was confirmed by complementation tests in which significant GAT-specific PFC and DTH responses were seen in (H-2q X H-2bm12)F1 hybrids, but not in (H-2q X H-2s)F1 hybrids. Suppressor T cells (Ts) also play a selective role in nonresponsiveness to GAT. Cyclophosphamide treatment of nonresponders (to eliminate Ts activity) as well as immunization with GAT coupled to the immunogenic carrier MBSA result in the development of GAT-specific humoral, but not CMI responses. Our results indicate that the T cell is the cellular site of Ir gene expression and that Tprlf responses do not correlate with functional helper T-cell activity and suggest distinct, multi-step Th/Ts regulatory pathways in the development of humoral and CMI effector functions.