Vβ Spectratype Analysis of Tissue-Infiltrating T Cells Responding to Minor Histocompatibility Antigens Involved in Graft-Versus-Host Disease.

Lethal graft-versus-host disease (GVHD) can be induced between MHC-matched murine strains expressing multiple minor histocompatibility antigen (miHA) differences. In the C57BL6 (B6)->BALB.B strain combination, both CD4⁺ and CD8⁺ donor T cells can mediate severe lethal GVHD, whereas in the B6->CXB-2 model, in which the CXB-2 strain expresses a subset of the BALB.B miHA, only the CD8⁺ T cells directly potentiate lethality. We have previously used TCR Vβ CDR3-size spectratype analysis to examine the alloreactive B6 CD4⁺ and CD8⁺ T cells, isolated from the lymphohematopoietic compartment after transplantation into both BALB.B and CXB-2 recipients. However, since tissue-specific expression of miHA can potentially elicit differential T cell responses, we have extended our T cell repertoire analysis to examine the responses involved in target tissue damage. Infiltrating host-presensitized B6 CD4⁺ and CD8⁺ T cells were isolated post-transplant from the intestines, livers and spleens of lethally irradiated (9 Gy; split-dose) BALB.B and CXB-2 recipients. The results indicated some overlapping Vβ CDR3-size skewing in both the CD4⁺ and CD8⁺ T cell repertoires between the BALB.B and CXB-2 recipients within the tissues of each recipient strain. Most notably, spectratype analysis demonstrated tissue specific responses unique to each of the BALB.B and CXB-2 infiltrates. In situ observations of the tissue infiltrating alloreactive T cells were performed by fluorescent microscopy of transplanted B6 T cells constitutively expressing eGFP into BALB.B and CXB-2 recipients, in conjunction with immunohistochemical staining of skewed Vβ families. TUNEL staining was also performed to confirm apoptosis of tissue epithelium. These analyses confirmed the increased infiltration of skewed CD4⁺ and CD8⁺ Vβ families within the target tissues.