The Mlsd-defined primary mixed lymphocyte reaction: a composite response to Mlsa and Mlsc determinants

Considerable disagreement exists among immunologists regarding the polymorphic nature of the murine Mls system. An estimate of the capacity of a given putative Mls allelic gene product expressed on a stimulator population to elicit proliferation of H-2-compatible Mls-disparate unprimed T cells may vary widely among different groups of investigators. This laboratory has shown previously that preactivation of B lymphocytes in a splenocyte stimulator population by exposure to goat anti-mouse IgD (GaMD) before irradiation dramatically enhanced the in vitro presentation not only of the strongly stimulatory (and highly cross-reactive) Mlsa and Mlsd, but also the more poorly stimulatory Mlsc specificity. Therefore, by the use of GaMD-treated splenocytes that optimally present the various Mls non-H-2 stimulatory epitopes, we attempted in this study to obtain a clearer understanding of Mls polymorphism by re-examining the conflicting claims associated with the mixed lymphocyte reaction (MLR) stimulatory capacity of different Mls specificities. Among H-2k responder cells of the Mls null, Mlsa, Mlsb, or Mlsd genotypes, only T cells from Mlsd-bearing CBA/J mice did not respond to Mlsc determinants present on GaMD-treated C3H/HeJ stimulator cells. Crossing CBA/J with an Mlsc-responsive mouse strain yielded an F1 animal in which nonresponsiveness to Mlsc was dominant. Although Mlsa (AKR/J) and Mlsc (C3H/HeJ) parental T cells both proliferated vigorously to Mlsd (CBA/J) stimulator cells, the Mlsa/c (AKR X C3H)F1 T cells responded poorly to GaMD-treated Mlsd stimulator cells. In addition, Mlsd (CBA/J) T cells were nonresponsive to Mlsa (AKR/J), Mlsc (C3H/HeJ), and Mlsa/c (AKR X C3H)F1 GaMD-treated stimulator cells. Because Mlsa (AKR/J) and Mlsc (C3H/HeJ) specificities are mutually stimulatory, at least limited polymorphism must exist in the Mls system. However, because Mlsa/c (AKR X C3H) and Mlsd (CBA/J) specificities are mutually nonstimulatory, T cell proliferation in an Mlsd-defined primary MLR is most likely due to a composite response to Mlsa and Mlsc epitopes present on CBA/J stimulator cells.     

T cell recognition of Mlsc. I. Influence of MHC gene products in Mlsc-specific T cell recognition

Monospecific T cell clones have been proven to be powerful tools for the characterization of T cell recognition in many Ag-specific as well as allo-specific T cell responses. In this report, in order to elucidate the mechanism of T cell recognition of minor stimulating locus Ag (Mlsc) determinants, Mlsc-specific cloned T cells were employed together with primary T cell responses to clarify the role of MHC-gene products in Mlsc-specific T cell recognition. The results indicated that T cells recognize Mlsc determinants in conjunction with I-region MHC gene products. Moreover, certain MHC haplotypes (e.g., H-2a and H-2k) appear to function efficiently in the "presentation" of Mlsc, whereas other haplotypes (e.g., H-2b and H-2q) function poorly if at all in presenting Mlsc. Experiments with the use of stimulators derived from F1 hybrids between the low stimulatory H-2b, Mlsc strain, C3H.SW, and a panel of Mlsb, H-2-different or intra-H-2 recombinant strains strongly suggested that expression of E alpha E beta molecules on stimulators plays a critical role for Mlsc stimulation. The functional importance of the E alpha E beta product in Mlsc recognition was further demonstrated by the ability of anti-E alpha monoclonal antibody to inhibit the response of cloned Mlsc-specific T cells. Inhibition of the same Mlsc-specific response by anti-A beta k antibody suggests that the A beta product may also play a role in T cell responses to Mlsc.     

T cell recognition of Mlsc,x determinants

Among a large number of cow insulin-specific T cell clones derived from both C57BL/10 and B10.A strains, several were found to react to non-MHC-linked gene products of a number of allogeneic strains. The stimulatory moiety for three of these clones correlates, in part, with expression of Mlsc, as defined by mouse strains C3H/HeJ and A/J. In addition, all three of these clones are stimulated by cells from strain PL/J, which has the poorly defined Mlsx allele. The data strongly suggest that Mlsx may, in fact, be Mlsc or is, at least, highly cross-reactive with Mlsc. Segregation analysis by using (B10.D2 X PL/J)F2 mice demonstrates that the Mlsx gene is genetically independent of the Mlsa linked Ly-9 marker on chromosome 1. Further studies with the use of these Mlsc,x-reactive clones reveal that they also recognize a gene product present in many mouse strains including DBA/2 which were previously phenotyped as Mlsa. However, testing of BxD recombinant inbred lines excludes Mlsa as being the stimulatory moiety. We therefore propose reclassification of the Mls phenotypes of several mouse strains based upon a two-locus model for Mls.     

Activation requirements of cloned inducer T cells. III. Need for two stimulator cells in the response of a cloned line to Mls determinants

To gain insight into the nature of Mls determinants, we examined the stimulator cells responsible for the activation of inducer T cell clones by Mls determinants. Two types of clones responding to Mls determinants were identified. One type responded to purified B cells, but not to splenic adherent cells (SAC), from mice bearing Mls stimulatory determinants. The other type of Mls-reactive T cell clone, including the representative clone Ly1-N5, demonstrated a vigorous response to unfractionated spleen cells, but showed little or no response to B cells alone or to SAC alone from mice bearing the Mlsa or Mlsd stimulatory determinant. The response of these clones to Mls determinants required stimulation by two cell types. The failure of clone Ly1-N5 to respond to Mlsa-bearing B cells was reversed by the addition of SAC taken from mice bearing the Mlsa allele. In addition, SAC from mice bearing the nonstimulatory Mlsb allele could synergize with B cells from Mlsa-bearing animals. B cells were required to provide the Mlsa determinant, because the combination of Mlsa-bearing SAC and Mlsb-bearing B cells did not activate the clone. The response of clone Ly1-N5 to Mls is restricted by Ia determinants (shared by H-2b, H-2d, and H-2k haplotypes but not by the H-2q haplotype). The permissive H-2 alleles can be present either on the stimulator B cell or on the SAC. The optimal response of the clone was obtained by using B cells bearing Mlsa and the permissive Ia epitopes. However, a significant response of the clone to B cells bearing Mlsa but an inappropriate Ia (Iaq) was also seen in the presence of SAC bearing the nonstimulatory Mlsb allele but the permissive Ia epitopes.     

Characterization of a new minor lymphocyte stimulatory system. I. Cluster of self antigens recognized by "I-E-reactive" V beta s, V beta 5, V beta 11, and V beta 12 T cell receptors for antigen.

In the mouse, two sets of V beta gene products have been shown to be associated with T cell recognition of endogenous self Ag. One of these is the set of V beta associated with T cell reactivities to stimulatory Mls gene products, Mlsa (V beta 6, V beta 8.1, V beta 9) or Mlsc (V beta 3); another is the set of V beta, such as V beta 5, V beta 11, V beta 12, or V beta 17a, which were originally found to be related to I-E recognition. Although the Mls system has been well characterized, little is known about the nature of the ligands for the second set of V beta. In this work, we describe the evidence that the natural ligand or ligands of V beta 5, V beta 11, and V beta 12 may be novel Mls determinants that are recognized by naive T cells at a high precursor frequency and function as the ligand for clonal deletion of self-reactive T cells by negative selection. However, surprisingly, unlike the conventional Mls system, in which all V beta associated with Mlsa recognition or Mlsc recognition are uniformly deleted in those animals expressing the relevant Mls type, expression of these three V beta segregates independently among strains. Based on these observations, the nature of T cell recognition for this new Mls gene product(s) is discussed.     

The immunobiology of the T cell response to Mls-locus-disparate stimulator cells. I. Unidirectionality, new strain combinations, and the role of Ia antigens

The primary mixed lymphocyte reaction of T cells to Mls-locus-disparate stimulator cells differs from that to non-self Ia antigens in several respects. In the present experiments, the unidirectional nature of this response is shown in several strain combinations, including the newly detected Mlsa and Mlsa-like alleles expressed by strains PL/J, RF/J, and SM/J. All of these strains stimulate MHC-identical T cells strongly. In addition, they stimulate a variety of cloned T cell lines specific for Mlsa,d, which can thus be shown to respond to Mlsa,d stimulators of the H-2b,d,k,u, and v haplotypes. Although these results suggest that primary T cell responses to Mlsa,d are unlikely to be MHC restricted, these primary responses are readily inhibited by monoclonal antibodies specific for the I-A and especially the I-E products borne by the stimulator cells, as well as by monoclonal antibodies specific for L3T4a on the responding T cells. This effect of anti-Ia antibodies is not overcome by exogenous interleukin 1. Thus, I-A and especially I-E molecules are centrally involved in the unidirectional primary T cell response to the potently stimulating Mlsa and Mlsd alleles expressed by cells of several different MHC haplotypes.     

T cell responses to Mls determinants are restricted by cross-reactive MHC determinants

The studies presented here investigated the relationship between T cell recognition of MHC-encoded products and non-MHC-linked Mls determinants. The first aspect addressed whether Mls-reactive T cells recognize Mls-encoded products alone or in association with MHC-encoded determinants. Initial studies used Mlsa-specific T cell clones that were generated by repeated stimulation of C57BL/6 or B10.A(5R) spleen cells with DBA/2 lymphoid cells. These clones recognized Mlsa on cells expressing MHC products of the H-2b, H-2d, and H-2k haplotypes, but not the H-2q haplotype. Thus, these cloned T cells were found to recognize Mlsa products in association with public but demonstrably polymorphic H-2 determinants. The question of whether T cell clones that were specific for self-H-2 determinants (autoreactive) or soluble antigen plus syngeneic H-2 (antigen-specific) could also be stimulated by Mlsa determinants was also addressed. A substantial proportion of the antigen-specific or autoreactive T cell clones tested were stimulated by Mlsa determinants. Furthermore, stimulation of these clones by Mlsa was H-2 restricted. The pattern of H-2-restricted recognition of Mlsa by these clones was not distinguishable from that observed in the Mlsa-specific T cell clones, nor was it influenced by the primary specificity or H-2 restriction pattern of a given clone. Although these findings provide a means of explaining the observation that Mls-reactive T cells exist at extremely high precursor frequencies, they also raise questions regarding the nature of the receptor structures which are used by a single T cell in the recognition of two or more apparently distinct stimuli.     

T cell lines with dual specificity for strong Mls and H-2 determinants

To examine the relationship of T cell specificity for Mls vs H-2 determinants, BALB/c (H-2d,Mlsb)(d,b) T cells were stimulated repeatedly in vitro with H-2-compatible, Mls-incompatible DBA/2(d,a) stimulators. This line of T cells gave strong mixed-lymphocyte reactions to the priming Mlsa determinants but, in addition, gave appreciable responses to various foreign H-2 determinants. When this T cell line was subsequently stimulated over a period of 2 mo with Mlsa-negative cells of a particular foreign H-2 haplotype, e.g., H-2k, the cells gave high responses to H-2k determinants but only very low responses to third-party H-2 determinants. Significantly, the cells retained high reactivity for Mlsa determinants. In other experiments, BALB/c T cells positively selected to Mlsa,d-negative H-2-incompatible stimulator cells retained high reactivity for Mlsa determinants. The implications of these findings are discussed.     

Characterization of the Mlsf system. I. A novel "polymorphism" of endogenous superantigens.

In addition to Mlsa (Mls-1a) and Mlsc (Mls-2a, Mls-3a), we and others have recently described a third set of stimulatory minor lymphocyte stimulating (Mls) determinants, which are ligands for "I-E related" V beta, V beta 5, V beta 11, and V beta 12. Although all V beta associated with the recognition of the conventional Mls determinants are, in general, uniformly deleted in those animals expressing relevant Mls, expression of Mlsf-related V beta reveals various deletion patterns among different strains. Here we describe extensive genetic studies to evaluate the relationship among the self-Ag responsible for clonal deletion of T cells bearing Mlsf-related V beta by using antibodies specific for TCR V beta chain. In addition, a panel of T cell clones specific for the Mlsf determinant were generated and employed to analyze the determinant specificity, which is recognized by Mlsf-reactive T cells in vitro as well as the role of class II molecules in T cell recognition of the Mlsf determinants. The results of these two independent approaches provide evidence that the Mlsf system is composed of a set of gene products that reveal a unique polymorphism in the induction of clonal deletion in vivo and in T cell activation in vitro. One of these gene products causes almost complete deletion of the self-Mlsf reactive T cell repertoire in vivo and elicits a strong proliferative response to Mlsf-specific T cell clones. Expression of the other gene products results in the clonal deletion of only part of the Mlsf-reactive T cell repertoire. Furthermore, the response pattern of Mlsf-specific clones to intra-MHC recombinant inbred strains and the inhibition pattern of these clones by anti-class II antibody suggested that although expression of the I-E molecule is essential for T cell recognition of Mlsf determinants, the A beta gene may also contribute to the efficient presentation of Mlsf determinants by forming unique class II E alpha A beta molecules.     

Immune responses in vitro. XIII. MLR detectability of Mlsa-, Mlsb-, Mlsc-, and Mlsd-encoded products

The Mls locus was originally defined to have four alleles; all controlled products that were detectable in MLR except b, which was described as being null. More recent evidence led other investigators to postulate that the Mls locus is nonpolymorphic, being composed of only the b null allele and a singly expressed allele previously ascribed to be the a and d alleles. Our results indicate that Mlsa and Mlsd control products that are antigenically distinct and, therefore, the products cannot be controlled by the same allele. In addition, the product of Mlsb was easily detectable by Mlsa and Mlsd responding cells and cannot be considered null. Alternative explanations are considered for these conflicting results.     

Nonresponsiveness to Mlsd in F1 hybrid mice carrying Mlsa and Mlsc genes

Neither the biological function nor a basic understanding of the enigmatic chromosome 1-encoded Mls locus of the mouse has yet been uncovered despite extensive investigations. The present report is a continuation of our genetic analyses of the Mls locus in an attempt to better define the system. Data presented here indicate that in contrast to cells of mice expressing either the Mlsa or Mlsc allele which respond in mixed leukocyte reactions to cells expressing the Mlsd allelic products, cells from (Mlsa X Mlsc)F1-hybrid mice do not. In addition, the nonresponder phenotype appears to segregate as a single autosomal genetic system in backcross animals. These findings fail to support two recently advanced hypotheses: first, that the Mls locus is nonpolymorphic, or second, that the Mls locus controls differential expression of Ia antigenic determinants. Although the mechanism by which a (responder X responder) converts to a nonresponder remains unknown, three models involving gene complementation are discussed.     

Genetic analysis of the presentation of minor lymphocyte-stimulating determinants. II. Differing non-MHC control of super-stimulatory and more poorly stimulatory Mls phenotypes

Analysis of the capacity of splenocytes from non-prototypic Mlsa or Mlsc mouse strains to stimulate allogeneic H-2k-compatible T cells in a primary Mls-defined MLR provided interesting examples of exceptions to the usually stated characterization of Mlsa and Mlsc determinants as highly stimulatory of weakly stimulatory, respectively. Across the Mlsa barrier, MA/My stimulator cells had a significantly reduced capacity to elicit responder proliferation in comparison with prototypic AKR/J or less well studied C58/J, CE/J, or RF/J splenocytes. Across the Mlsc barrier, a gradient of stimulatory ability was observed with RF/J splenocytes being virtually nonstimulatory, prototypic C3H/HeJ splenocytes having an intermediate capacity, and CE/J and C58/J being highly stimulatory presenters of this non-MHC specificity. The differing capacity of each of these H-2k stimulator cells to elicit unprimed responder cell proliferation across an Mlsa or Mlsc difference correlated with the T cell growth factor activity that was secreted into the MLR supernatants. The super stimulatory form of Mlsc was expressed in an autosomal dominant fashion by (Mlsc poorly stimulatory x Mlsc super-stimulatory)F1 animals, (BALB.K x C58/J)F1 or (RF/J x CE/J)F1. The segregation of Mlsc stimulatory ability among first backcross and F2 animals derived from the former F1 was compatible with a single non-MHC gene controlling the expression and presentation of the super-stimulatory form of Mlsc. The regulatory nature of this gene was indicated by the observation that F1 animals generated from the Mlsc nonprototypic and poorly stimulatory BALB/c parental strain were self-tolerant to the super-stimulatory form of Mlsc. The existence of an Mls specificity other than a and c was suggested by positive non-MHC MLR responses in certain responder/stimulator cell combinations of Mls prototypic and nonprototypic mouse strains.     

Isolation and characterization of an I-A-restricted T cell clone with dual specificity for poly(Glu60Ala30Tyr10) (GAT) and Mlsa,dl

We have isolated a BALB/c (H-2d, Mlsb) T cell clone (JTL-G12) specific for the synthetic polypeptide antigen poly(Glu60Ala30Tyr10) (GAT) in the context of self I-A determinants and for Mlsa,d antigens in the absence of GAT. JTL-G12 proliferation in response to GAT was mapped to the Kd, I-Ad subregions by using inbred H-2 congenic and recombinant strains. In addition, monoclonal antibody directed against I-Ad but not Kd or I-As determinants blocked JTL-G12 proliferation in response to GAT presented by syngeneic splenocytes, indicating I-A restriction. The Mls cross-reactivity of this clone was verified by using a panel of inbred strains bearing the Mlsa,b,c,d alleles and by using BXD recombinant inbred strains bearing the Mlsa allele or the Mlsb allele. All of the Mlsa BXD strains of the H-2d or H-2b haplotypes stimulated JTL-G12 in the absence of GAT, whereas all of the Mlsb BXD strains were nonstimulatory. This response pattern is in complete accordance with recognition of the Mlsa determinant encoded by Mls or closely linked loci on chromosome 1. JTL-G12 proliferation in response to GAT/I-Ad and Mlsa,d determinants could be blocked with a monoclonal antibody (GK1.5) directed against L3T4, a structure involved in class II major histocompatibility complex antigen recognition. These results suggest that antigen/class II responsiveness, Mls reactivity, and expression of L3T4 can be properties of a single T cell population.     

The role of dendritic cells as stimulators of minor lymphocyte-stimulating locus-specific T cell responses in the mouse. I. Differential capacity of dendritic cells to stimulate minor lymphocyte-stimulating locus-reactive T cell hybridomas and the primary anti-minor lymphocyte-stimulating locus mixed lymphocyte reaction

The response of T cells to minor lymphocyte-stimulating locus (Mls) determinants remains poorly understood with respect to the antigenic determinants responsible for T cell stimulation and the types of APC capable of stimulating the response. In this report, we demonstrate that highly purified dendritic cells (DC) as well as B cells have the capacity to stimulate Mls-specific responses. Unseparated spleen cells, purified DC, resting B cells, and activated B cells were compared for their capacity to stimulate several Mls-reactive T cell hybridomas. Whereas the entire panel of Mls-reactive T cell hybridomas was stimulated strongly by unseparated spleen cells and activated B cells, the hybridomas responded only weakly to purified DC or resting B cells. Activation of resting B cells with either B cell stimulatory factor-1 (1 day pre-treatment) or LPS/dextran (2 or 3 day pre-treatment) greatly augmented their Mls-stimulatory capacity. In contrast, the Mls-stimulatory capacity of DC was not augmented by a 1-day pre-treatment with either B cell stimulatory factor-1 or supernatant from the DC-induced primary anti-Mls-MLR. In the primary anti-Mls-MLR, both purified DC and LPS/dextran-stimulated B blasts were found to elicit vigorous T cell proliferative responses. Much weaker responses were elicited by unseparated spleen cells. The stimulation of the primary anti-Mls-MLR by purified DC was further confirmed by producing Mls-specific T cell clones which were preferentially stimulated by DC. Autologous (Mlsb) DC were found to markedly enhance the primary anti-Mls-MLR response to small numbers of Mlsa B blasts. Thus, DC possess other "accessory cell" properties that augment the primary anti-Mls-MLR despite the predicted low level of Mls determinant expression on DC based on the results obtained with Mls-reactive hybridomas. Possible accessory cell properties of DC relevant to this phenomenon are discussed.     

Effect of Mlsa on antigen presentation to class II-restricted T cells

The nature of the gene products encoded or regulated by the minor lymphocyte-stimulating (Mls) loci remains enigmatic despite extensive experimental evaluation. This work tested the hypothesis that the Mlsa genotype, when compared to the Mlsb genotype, facilitates Ag presentation to class II-restricted T cells. Titrated numbers of H-2-identical, Mls-disparate APC were used to stimulate proliferation of autoreactive, alloreactive, or Ag-specific class II-restricted T cell clones or lines. Apparent preferential presentation by Mlsa vs Mlsb APC obtained from H-2-identical strains was seen infrequently, and when observed, analysis with the use of APC from recombinant inbred lines revealed that preferential presentation did not correlate with the Mls genotype of the APC. These studies show that the Mlsa genotype does not influence overall Ag presentation to class II-restricted T cells.     

The immunobiology of T cell responses to Mls-locus-disparate stimulator cells. II. Effects of Mls-locus-disparate stimulator cells on cloned, protein antigen-specific, Ia-restricted T cell lines

Cloned, protein antigen-specific, Ia-restricted T cell lines frequently (approximately 20%) also respond strongly to stimulator cells from strains expressing stimulatory alleles at the chromosome 1-encoded Mls-locus. Furthermore, such responses are blocked by monoclonal antibodies specific for Ia antigens expressed by the stimulator rather than the responder cells. However, such responses show no specificity for polymorphic determinants on Ia molecules, although in such responses, as in primary and secondary T cell responses to stimulating Mls-locus alleles, I-E molecules appear to play a central role. These results, combined with the unique immunobiology of the primary T cell proliferative response to Mls-locus-disparate stimulator cells, suggest to us that this response involves the interaction of the receptor on T cells for antigen:self Ia with a relatively nonpolymorphic region of Ia glycoproteins. This hypothesis is supported by the observation that a monoclonal antibody to the T cell receptor will inhibit both responses, although the response to Mls-locus-disparate stimulators appears to be more sensitive to these antibodies. We propose that the interaction of the T cell receptor with Ia is stabilized by a cell interaction molecule encoded or regulated by the Mls-locus gene product permitting the T cell receptor:Ia glycoprotein interaction to lead to T cell activation.     

The role of H-2 in T cell recognition of Mls

The role of H-2 was evaluated in T cell recognition of Mls-encoded antigens during primary mixed lymphocyte responses (MLR). Mlsc was used as a stimulating determinant in MLR and its recognition by T cells was assessed by linear regression analysis under culture conditions in which (A x B)F1 responder cell number was the factor limiting total response. Results of such experiments indicated the presence of distinct (A x B)F1 responder T cell subpopulations capable of differentially recognizing the foreign Mls antigen in association with one or the other parental H-2 haplotype. These findings demonstrate that T cells do not recognize Mlsc products in isolation, but rather are restricted to recognition of Mlsc in the context of "self" H-2 determinants.     

Altered expression of self-reactive T cell receptor V beta regions in autoimmune mice.

Intrathymic tolerance results in elimination of T cells bearing self-reactive TCR V beta regions in mice expressing certain combinations of I-E and minor lymphocyte stimulatory (Mls) phenotypes. To determine if autoimmune strains of mice have a defect in intrathymic deletion of self-reactive TCR V beta regions, expression of V beta 3, V beta 6, V beta 8.1, and V beta 11 were examined in lpr/lpr and +/+ strains of mice; MRL/MpJ(H-2K, I-E+, Mlsb,), C57BL/6J(H-2b, I-E-, Mlsb,), C3H/HeJ(H-2k, I-E+, Mlsc), AKR/J(H-2k, I-E+, Mlsa); and in autoimmune NZB/N(H-2d, I-E+, Mlsa) and BXSB(H-2b, I-E-, Mlsb) mice. The results suggest that, during intrathymic development, self-reactive T cells are deleted in autoimmune strains of mice as found in normal control strains of mice. However, the TCR V beta repertoire is skewed in autoimmune strains compared to normal strains of mice. For example, MRL-lpr/lpr mice, but not other lpr/lpr strains, had increased expression of V beta 6 relative to expression in control MRL(-)+/+ mice, which is associated with collagen-induced arthritis. These data are consistent with a model of normal affinity for negative selection of self-reactive T cells in the thymus of autoimmune strains of mice followed by expansion of autoreactive T cell clones in the peripheral lymphoid organs. The peripheral lymphoid organs of lpr/lpr mice contain an expanded population of abnormal CD4-, CD8-, 6B2+ T cells. Elimination of self-reactive peripheral T cells suggests that these abnormal cells are derived from a CD4+ subpopulation in the thymus. Flow cytometry analysis of peripheral lymph node T cells from MRL-lpr/lpr mice reveal three populations of CD4+ T cells expressing low, intermediate and high intensity of B220 (6B2). This supports the hypothesis that in lpr/lpr mice, self-reactive CD4+ T cells are eliminated in the thymus, and that these cells lose expression of CD4 and acquire expression of 6B2 in the periphery.     

The expression of Mls c determinants on Mls a,Mls b,and Mls x prototypic strains

In the mouse sytem, specific determinants other than major histocompatibility complex (MHC) gene products are capable of inducing strong primary proliferative responses in naive T cells. These determinants are encoded by at least two gene loci designated as minor lymphocyte stimulatory (Mls) loci. In order to elucidate the biological role of the Mls system, an effort has been initiated to clarify the fundamental immunogenetic characteristics of the Mls system. In this report, we describe the unexpected finding that Mls ^c determinants are expressed on splenocytes of strains including those which have been used as prototypic examples of three other Mls types: Mls ^a (DBA/2, DBA/1), Mls ^b , (BALB/c), and Mls ^x (PL/J). The expression of Mls ^c by these strains was demonstrated both by the response patterns of unprimed T cells from MHC-identical inbred or F₁ hybrid strains and by the responses of a panel of Mls-specific T-cell clones. The experimental results reported here also suggest that the expression of Mls determinants may be influenced by multiple other genes, including MHC-linked genes.Abbreviations used in this paper MHC major histocompatibility complex - MLR mixed lymphocyte reaction - Mls minor lymphocyte stimulating locus antigen - MMC mitomycin C - NNT nylon wool nonadherent T cells     

Neonatal tolerance induction to Mlsa. II. T cells induce tolerance to Mlsa

We have investigated the ability of murine T cell lines to induce neonatal tolerance to Mlsa (minor lymphocyte stimulating). Mlsb mice were injected within 24 hr of birth with MHC (major histocompatibility complex) identical T cell lines generated by culturing responders from Mlsa strains with stimulators from Mlsb strains. Injected mice were tested at 6 to 8 weeks of age for responses in either primary mixed leukocyte reaction or IL-2 limiting dilution analysis. Mlsa specific responses by injected tolerant mice relative to noninjected controls were reduced by 92-98% in MLR and by 2- to 10-fold in IL-2 LDA. In contrast, responses against third-party MHC antigens by either the injected or the noninjected mice were identical. Fifty percent of all mice injected with the T cell lines were tolerant to Mlsa. These results strongly suggest that murine T cells express the Mlsa gene product.