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S M Hedrick

Publications and source records attributed to S M Hedrick.

88 records · Page 5Linked to original sources
PubMed1985

Rearrangement and transcription of a T-cell receptor beta-chain gene in different T-cell subsets.

The functionally defined sets of T lymphocytes--helper T cells, cytotoxic T cells, and suppressor T cells--were examined for the possible involvement of a recently identified T-cell receptor beta gene locus in receptor formation. Since gene rearrangements are required for functional gene expression, cloned T-cell lines from each of the groups were surveyed for the expression of unique gene rearrangements. In addition, cell lines that showed gene rearrangements were further tested for the expression of the mature 1.2- to 1.3-kilobase mRNA transcribed from a productive gene rearrangement. The results of such experiments show that helper and cytotoxic T cells may use a common beta chain of the receptor, whereas suppressor cells do so rarely, if at all.

Animals↗
PubMed1984

Murine T cell receptor beta chain is encoded on chromosome 6.

Southern blot analysis of somatic cell hybrid lines indicates that the beta chain of the T cell receptor for antigen maps to chromosome 6 of the mouse. An experiment testing hybridization of the constant region of this gene to DNA from a hybrid cell line containing a translocation of chromosome 6 supports the localization of this gene to the proximal (centromeric) one-third of chromosome 6, in the same general region as the immunoglobulin kappa chain locus. This may be another indication of the shared evolutionary origins of the genes encoding both T and B cell antigen recognition.

Animals↗
PubMed1984

A murine T cell receptor gene complex: isolation, structure and rearrangement.

We describe here our efforts to develop a systematic strategy for the enumeration and isolation of genes encoding T cell-specific, membrane-associated polypeptides. Of particular importance among the cDNA clones that we have isolated is one which encodes the beta chain of the murine T cell receptor for antigen. The gene product is strikingly similar to immunoglobulin in its variable (V), constant (C), joining (J), and diversity (D) - like elements and the ability of the latter three types of element to assort independently during differentiation. The genomic organization of the constant region locus which encodes this molecule consists of two tandemly arrayed units of the form JC/JC, where the J clusters consist of fourteen distinct elements, many of which may be functional. The two constant regions differ by only four amino acids and both are apparently expressed in T cells of the same phenotype, so they probably do not represent isotypes in the classical sense. The sequences flanking the V, D and J elements are also similar to the conserved heptamer and nonomer sequences of immunoglobulins thought to be important in the recombination of the specific gene segments. These similarities indicate both the common evolutionary origins of these loci and the strong selective pressure that must be operative. The T cell receptor locus differs somewhat from immunoglobulins in the large number of possible J region elements and to some extent in the hypervariable-framework regions of the V region. We and others have mapped this gene to chromosome 6 of the mouse, in the same portion of the chromosome but not closely linked the kappa locus. The significance of the predicted protein structure of the beta chain and its support of the one-receptor model of MHC-antigen recognition are discussed.

Amino Acid Sequence↗
PubMed1983

The T cell response to allelic determinants on Igh-1-encoded IgG2a antibodies: dual recognition examined by using antigenic antibodies with binding affinity for Ia molecules.

In this report we examine the effects of binding antigen directly to Ia molecules during immunization and stimulation of T cells in culture. To accomplish this we characterize the T cell response to Igh-1j-encoded IgG2a antibodies in C57BL/10 H-2 congenic mice. In contrast to the response to the closely related Igh-1a-encoded IgG2a antibodies, high responder mice were (C57BL/10 X B10.A)F1 hybrids, and the important alleles appeared to map to I-Ab and I-Ak. C57BL/10 and B10.A(5R) strains were low responders (I-Ab), and B10.A and B10.A(4R) strains were nonresponders (I-Ak). The interest in using monoclonal IgG2a antibodies as T cell antigens was that different V-region-encoded binding specificities could be associated with the same IgG2a antigenic determinant. In our interpretation of the Langman and Cohn dual binding site model of the T cell receptor, the response to anti-Ia antibody should have some of the same characteristics as that to an allogeneic Ia molecule; in particular, it should be non-H-2-restricted. Although the response to anti-Ia antibody had several interesting properties, no difference in the restriction specificity was found for the T cell response to anti-Ia antibodies relative to unreactive IgG2a antibodies. Our conclusion is that T cell receptors must bind both Ia and antigen molecules for activation to occur. In a separate set of experiments, the T cell response resulting from immunization with anti-Ia antibody was examined. Because the antigen was shown to be associated with the Ia molecule during immunization, experiments were designed to detect an alteration or lack of H-2 restriction in the resulting T cell population. A long-term T cell line induced after such immunization showed no qualitative differences from a T cell line produced with unreactive IgG2a antibody. These results demonstrate that simply attaching a foreign antigen to a restriction element is not sufficient to lead to unrestricted T cell activation. This in turn suggests the T cell receptor must recognize the restriction element for cell-cell interactions to occur.

Alleles↗
PubMed1982

Immune response gene function correlates with the expression of an Ia antigen. II. A quantitative deficiency in Ae:E alpha complex expression causes a corresponding defect in antigen-presenting cell function.

A series of experiments were performed to explore the role of complementing major histocompatability complex (MHC)-linked immune response Ir genes in the murine T cell proliferative response to the globular protein antigen pigeon cytochrome c. The functional equivalence of I-E-subregion-encoded, structurally homologous E(a) chains from different haplotypes bearing the serologic specificity Ia.7 was demonstrated by the complementation for high responsiveness to pigeon cytochrome c of F(1) hybrids between low responder B 10.A(4R) (I-A (k)) or B 10.S (I-A(8)) mice and four low responder E(a)- bearing haplotypes. Moreover, this Ir gene function correlated directly with both the ability of antigen-pulsed spleen cells from these same F(1) strains to stimulate pigeon cytochrome c-primed T cells from B10.A or B10.S(9R) mice, and with the cell surface expression of the two-chain Ia antigenic complex, A(e):E(a), bearing the conformational or combinatorial determinant recognized by the monoclonal anti-Ia antibody, Y-17. The B 10.PL strain (H-2(u)), which expresses an Ia.7-positive I-E- subregion-encoded E(a) chain, failed to complement with B10.A(4R) or B10.S mice in the response to pigeon cytochrome c. However, (B10.A(4R) x B10.PL)F(1) and (B10.S x B10.PL)F(1) mice do express A(k)(e):E(u)(a) and A(8)(e):E(u)(a) on their cell surface, although in reduced amounts relative to A(k,s)(e):E(k,d,p,r)(a) complexes found in corresponding F(1) strains. This quantitative difference in Ia antigen expression correlated with a difference in the ability to present pigeon cytochrome c to B 10.A and B 10.S(9R) long-term T cell lines. Thus, (B10.A(4R) x B10.PL)F(1) spleen cells required a 10-fold higher antigen dose to induce the same stimulation as (B10.A(4R) x B10.D2)F(1) spleen cells. In addition, the monoclonal antibody, Y-17, which reacts with A(e):E(a) molecules of several strains, had a greater inhibitory effect on the proliferative response to pigeon cytochrome c of B10.A T cells in the presence of (B10.A(4R) X B10.PL)F(1) spleen cells than in the presence of (B10.A(4R) X B10.D2)F(1) spleen cells. These functional data, in concert with the biochemical and serological data in the accompanying report, are consistent with the molecular model for Ir gene complementation in which appropriate two-chain Ia molecules function at the antigen-presenting cell (APC) surface as restriction elements. Moreover, they clearly demonstrate that the magnitude of the T cell proliferative response is a function of both the concentration of nominal antigen and of the amount of Ia antigen expressed on the APC. Finally, the direct correlation of a quantitative deficiency in cell surface expression of an Ia antigen with a corresponding relative defect in antigen-presenting function provides strong independent evidence that the I-region-encoded Ia antigens are the products of the MHC-linked Ir genes.

Animals↗
PubMed1982

The fine specificity of antigen and Ia determinant recognition by T cell hybridoma clones specific for pigeon cytochrome c.

The activation of proliferative T lymphocytes normally involves the simultaneous recognition of a particular foreign antigen and a particular Ia molecule on the surface of antigen-presenting cells, the phenomenon of major histocompatibility complex (MHC) restriction. An analysis of T cell clones specific for pigeon cytochrome c, from B10.A and B10.S(9R) strains of mice, revealed the unusual finding that several of the clones could respond to antigen in association with Ia molecules from either strain. Using these cross-reactive clones, we performed experiments which demonstrated that both the Ia molecule and the T cell receptor contribute to the specificity of antigen recognition; however, MHC-linked low responsiveness to tuna cytochrome c (an immune response gene defect) could not be attributed solely to the efficacy with which the Ia molecules associated with the antigen. These results imply that antigen and Ia molecules are not recognized independently, but must interact at least during the process of T cell activation.

Animals↗
PubMed1980

Genetic control of the immune response to collagen. I. Quantitative determination of response levels by multiple I-region genes.

The antibody response in mice to type I calf skin collagen is quantitatively determined by genes with map to the I region of the H-2 histocompatibility complex. The use of H-2 recombinant B10 congenic strains of mice reveals that a gene in the IA subregion and a gene to the right of the IA subregion affect responsiveness. To examine complementation patterns in the antibody response to collagen, five B10 congenic strains, each bearing an independent H-2 haplotype, were intercrossed to obtain nine hybrid strains heterozygous at the H-2 locus. In five combinations heterozygous progeny produced significantly greater antibody responses than those observed for the homozygous parental strains. Two low responder haplotypes, H-2k and H-2d, were shown to be qualitatively different. Mice of these haplotypes show a different dose--response pattern and a different phenotypic pattern of inheritance with respect to the high responder H-2b haplotype. Complementation effects found in F1 hybrid mice derived from H-2 recombinant parental strains indicate that high responsiveness, controlled by an IA6 subregion gene, can be influenced by an interaction between an IAk subregion gene and an ICd subregion gene on different chromosomes. These data are consistent with the possibility that there exist two or more I region genes that have distinct functions and can interact to affect the levels of immune responsiveness.

Alleles↗
PubMed1980

Genetic control of the immune response to collagen. III. Coordinate restriction of cellular cooperation and antigen responsiveness by thymus-directed maturation.

The H-2 restriction of T helper cells from thymus-reconstituted nude mice was examined. Hybrid athymic mice were bred from BALB/c.nu and C57BL/6.nu parental strains and reconstituted with fetal thymus tissue from either parental strain. T helper cells from these mice, immunized to SRBC, were restricted to cooperation with B cells of the thymic H-2 haplotype. These T helper cells were shown to have originated from the F1 host by functional sensitivity to antisera and complement. The H-2 restriction of thymus-reconstituted F1 nude mice was further investigated by examining expression of the Ir-collagen phenotype. Results showed that the level of antibody produced in response to type I calf collagen in thymus chimeras correlates with the H-2 haplotype (high responder or low responder) of the reconstituting thymus. These experiments indicate that the thymus environment of T cell maturation influences both the H-2 restriction and Ir-phenotype of a responding immune system.

Animals↗
PubMed1979

Genetic control of the immune response to collagen. II. Antibody responses produced in fetal liver restored radiation chimeras and thymus reconstituted F1 hybrid nude mice.

The level of antibody produced in response to calf skin collagen in mice is influenced by genes which are closely linked to the I region of the H-2 major histocompatibility complex. This influence is shown to be expressed during lymphoid maturation by testing the antibody responsiveness to collagen in two types of chimeric mice. First, high responder and low responder parental strain mice were lethally irradiated and restored with fetal liver cells from (high X low responder) F1 mice. These F1 leads to parent chimeras exhibited an immune response phenotype characteristic of the irradiated parental strain animals, establishing that H-2 determinants of the host affect antigen responsiveness. Second, (high X low responder) F1 congenitally athymic (nude) mice were restored with fetal thymus transplants from either high or low responder parental strain mice. After a period of maturation these mice were shown to be competent for a T-dependent IgG response to SRBC. The responsiveness to collagen in these mice was characteristic of the parental strain thymus donors, indicating that the expression of H-2 determinants in thymic tissue during lymphoid maturation influences the antibody response phenotype expressed by mice.

Animals↗
PubMedDate not supplied

Isolation of cDNA clones encoding T cell-specific membrane-associated proteins.

Of 10 distinct cloned DNA copies of mRNAs expressed in T lymphocytes but not in B lymphocytes and associated with membrane-bound polysomes, one hybridizes to a region of the genome that has rearranged in a T-cell lymphoma and several T-cell hybridomas. These characteristics suggest that it encodes one chain of the elusive antigen receptor on the surface of T lymphocytes.

Animals↗
PubMedDate not supplied

Sequence relationships between putative T-cell receptor polypeptides and immunoglobulins.

Comparison of the sequence of a cloned T cell-specific cDNA with those of cross-reacting cloned cDNAs isolated from a thymocyte library indicates the presence of variable, constant and joining regions remarkably similar in size and sequence to those encoding immunoglobulin proteins. Together with the evidence for somatic gene rearrangements reported in the accompanying paper, this strongly suggests that the TM86 cDNA clone encodes one chain of the T-cell receptor for antigen.

Amino Acid Sequence↗
PubMedDate not supplied

Isolation of a cDNA clone corresponding to an X-linked gene family (XLR) closely linked to the murine immunodeficiency disorder xid.

The striking number of human and murine immunodeficiency disorders which map to the X chromosome suggests that genes localized on this chromosome must have important roles in lymphocyte development. At least seven distinct disorders in the human and two in the mouse disrupt lymphocyte maturation, particularly that of B cells, at characteristic stages. As functional genes mapping to the X chromosome in one mammal are found on the X chromosome in all other mammals, the same genes regulating lymphocyte development are expected to be found on the X chromosome in mouse and man. Investigations into the possible mechanisms of these X-linked disorders have been hampered by the lack of molecular probes for the genes or gene products affected; because of this, and the possibility of correlating one or more of the several hundred B- or T-cell-specific genes with a specific mutation, we surveyed 15 different B- and T-cell-specific cDNA clones for localization to the X chromosome. We report here the characterization of one of these murine cDNA clones, which hybridizes with a large, X-linked gene family, designated XLR (X-linked, lymphocyte-regulated). We show that the XLR gene family is closely linked to the X-linked immunodeficiency described in the CBA/N mouse strain (xid), by restriction fragment length polymorphism (RFLP) analysis of DNA from mice congeneic for xid. This finding, together with data on the expression of the XLR locus in B cells, indicates that this gene family either includes the locus defined by the xid mutation or is adjacent to it in a gene complex which may be important in lymphocyte differentiation.

Animals↗
PubMedDate not supplied

Correlations between T-cell specificity and the structure of the antigen receptor.

The derived amino-acid sequences of the heterodimeric antigen receptors expressed by a series of murine T-cell clones are presented. A comparison of the receptor sequences indicates that several mechanisms for generating receptor diversity can influence T-cell specificity, including junctional diversity, combinatorial joining, and combinatorial chain associations.

Amino Acid Sequence↗