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Biomedical subjects

H D Hunt

Publications and source records attributed to H D Hunt.

5 recordsLinked to original sources
PubMed1992

Alloreactive cytotoxic T lymphocytes recognize epitopes determined by both the alpha helices and beta sheets of the class I peptide binding site.

A chimeric class I glycoprotein was created to investigate the functional contribution of the alpha helices and the beta-pleated sheets in forming the antigen recognition site (ARS) of antigen-presenting molecules. This novel molecule was generated by replacing the DNA sequences encoding the alpha helices of the Ld gene with the corresponding sequences from the Kb gene. Serologic analysis of transfected L cells that expressed the chimeric molecule (Kb alpha Ld beta) revealed that the engineered class I glycoprotein retains two conformational epitopes associated with the alpha helices of Kb, as defined by monoclonal antibodies K10.56 and 28-13-3. These results demonstrate that the alpha helices of Kb can associate with the beta-pleated sheets of Ld to form a stable structure, which is expressed on the cell surface. To address the role of the alpha helices of the ARS in determining T cell crossreactivity, alloreactive cytotoxic T lymphocytes (CTL) were used to analyze L cells expressing Kb alpha Ld beta. CTL raised against Kb or Ld as alloantigens showed little, if any, ability to lyse L cells expressing Kb alpha Ld beta. Thus, alloreactive CTL did not recognize structures determined by the alpha helices alone or by the beta sheets of the ARS alone. However, bulk and cloned alloreactive CTL that were generated against the mutant Kb glycoprotein Kbm8 reacted strongly with Kb alpha Ld beta. In addition to the Kb alpha helices, the Kbm8 ARS shares a single polymorphic amino acid at position 24 with Kb alpha Ld beta. Amino acid 24 is located on the beta 2 strand that forms part of the floor of the ARS and has been identified as a component of pocket B in the HLA class I ARS. The substitution of Glu to Ser at this position was shown previously to be the central determinant of the Kbm8 mutant alloantigenicity. The functional significance of this position in determining crossreactivity between bm8 and Kb alpha Ld beta identifies pocket B as a strong anchor for allogenic self-peptides. These findings demonstrate that determinants recognized by CTL on class I alloantigens are formed by interactions involving both the alpha helices and beta sheets of the ARS. These interactions are best explained by the influence of the alpha helices and beta sheets on the peptide-binding properties of these antigen-presenting molecules.

Animals↗
PubMed1992

Identification of functional T cell subsets and surface antigen changes during activation as they relate to RT6.

The functional and phenotypic heterogeneity of the rat peripheral T lymphocyte antigen RT6 has been examined. The in vivo popliteal graft-vs-host reaction (GvHR), in vitro MLR, and the generation and effector populations of cytotoxic T lymphocyte were used to examine the response of RT6-positive (RT6+) or -negative (RT6-) subsets of CD4 and CD8 T cells to alloantigen. T lymphocytes with the CD4+RT6+ surface phenotype are necessary and sufficient for inducing a strong GvHR. T lymphocytes with the CD4+RT6-, CD8+RT6+, and CD8+RT6- surface phenotypes do not contribute or induce a strong GvHR. Both the CD4+RT6+ and the CD4+RT6- T cells proliferate in the MLR assay. CTL precursors are a mixture of CD8+RT6+ and CD8+RT6- phenotypes, but only cells bearing the RT6- phenotype are potent CTL effector cells. Data presented in this paper also demonstrate that the RT6.1 alloantigen, present on the majority of rat T cells, modulates on cortisone-resistant thymocytes (CRT) and peripheral T cells. Although freshly isolated CRTs do not express the RT6.1 epitope, RT6+ cells develop when CRTs are placed into culture. Peripheral T cells that are RT6- will also become RT6+ in culture. Stimulation of T cell cultures with a mitogen causes the loss of the RT6.1 antigen, as detected by the DS4.23 mAb. The effect is more pronounced in cultures of CRTs than peripheral T cells. Following a return to a nonactivated state, the T cells reexpress RT6. The loss and reexpression of RT6 may be related to activation and/or differentiation of T cells.

ADP Ribose Transferases↗
PubMed1991

Peptide interactions with the Kb antigen recognition site.

The ability of OVA-specific H-2Kb-restricted CTL to recognize the defined OVA258-276 peptide in the context of the Kbm mutants and variants of these mutants was examined to determine how specific variations in the Ag recognition site-influenced peptide presentation to these CTL. L cells expressing Kb or Kbm10 were equally capable of presenting the OVA peptide to Kb-restricted, OVA-specific bulk CTL, whereas L cell clones expressing Kbm8 or Kbm1 showed little to no capacity to present this peptide. L cell transfectants expressing Kbm3 and Kbm23 consistently demonstrated an intermediate to low level of presentation to bulk OVA-specific CTL. Dissection of the Kbm8 mutant revealed that cells expressing Kbm8-22 (Tyr----Phe) and/or Kbm8-24 (Glu----Ser) presented the OVA peptide significantly less well than the Kb-presenting molecule. Presentation of OVA by cells expressing Kbm8-23,30 (Met----Ile) (Asp----Asn), Kbm8-23 (Met----Ile), and Kbm8-30 (Asp----Asn) was equivalent to Kb presentation. Another mutation designated as Kbm5, that has a substitution at position 116 (Tyr----Phe), demonstrated an intermediate to high ability to present OVA258-276 to an OVA-specific CTL line. The Kbm3, Kbm11, and Kbm23 mutants were unable to present the OVA peptide to this same CTL line. Dissection of these mutants showed that the substitution at position 77 (Asp----Ser), which is shared by all three mutants, was responsible for their inability to present the peptide. A second Kb-restricted CTL line was able to recognize OVA in the context of the Asp----Ser substitution at position 77. The results of this analysis suggest that the OVA258-276 peptide interacts with multiple regions within the Ag recognition site of the Kb class I protein.

Amino Acid Sequence↗