Date of Award

1996

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (Medical Science)

Department

Microbiology, Molecular Biology and Biochemistry

First Advisor

Bob Korngold

Second Advisor

Arthur Buchberg, Ph.D

Third Advisor

Laurence Eisenlohr, V.M.D., PhD

Fourth Advisor

Tim Manser, Ph.D

Fifth Advisor

Bice Perussia, M.D.

Abstract

Graft-versus-host-disease (GVHD) is a major complication of major histocompatibility complex (MHC) matched bone marrow transplantation. GVHD is the result of an immune-mediated attack, by T lymphocytes derived from donor bone marrow, against recipient tissues expressing minor histocompatibility antigen (miHA) differences. There is a lack of knowledge concerning the nature of in vivo immune responses to miHA during GVHD. C57BL/6By (B6/By) and BALB.B mouse strains both express the H-2B MHC haplotype but differ at more than 40 miHA loci. Both the in vitro and in vivo T cell responses to miHA expressed by BALB.B and CXB recombinant inbred (RI) strains of mice (CXBE, G, I, J and K) are governed by immunodominance. There are disparities between the hierarchies of in vitro and in vivo immunodominant T cell responses to BALB.B derived miHA.

The focus of this thesis work was to investigate the nature of T cell responses to miHA in a mouse model of GVHD and to determine what role immunodominance had in GVHD responses. The first part of the this work demonstrated that the discrepancy between in vitro and in vivo immunodominant T cell responses was not due to a differential requirement of T cell subsets. One hypothesis accounting for the discrepancy was that in vitro responses required CD8+CTL while in vivo responses were mediated by the CD4+T helper (Th) cell subset. Both CD4+ and CD8+ B6/By T cells were active in GVHD responses in BALB.B and all of the CXB RI strains. The second part of this work investigated the role of immunodominance in GVHD induction. MiHA-specific T cell blasts positively selected from thoracic duct lymphocytes (TDL) collected from BALB.B and CXBE mice injected with B6/By T cells were analyzed for Vbeta T cell receptor (TCR) usage. During the period of 4-6 days post-transplant, only CD4+ T cells exhibited noticeable shifts in expansion and Vbeta utilization. CD4+Vbeta6+ and CD4+Vbeta8.1, 8.2+ T cells were selectively expanded in B6/By anti-BALB.B TDL. In contrast, B6/By anti-CXBE TDL contained expanded CD4+Vbeta7+ and CD4+Vbeta9+ T cells. The different TCR repetoires in the two strains combinations suggested that B6/By CD4+ T cells recognized differentially expressed immunodominant miHA during GVHD induction. Results of PCR-based spectratyping and cDNA sequencing of anti-BALB.B CD4+ TDL T cell Vbeta6 TCR demonstrated CDR3 size skewing and biased usage of Jbeta1.3 and Jbeta2.4 gene segments. These results are evidence of oligoclonal expansion by miHA-specific effector CD4+ T cells during GVHD induction.

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