Background.

Minor histocompatibility antigens play a significant role in allograft rejection when donor and recipient are matched at MHC loci. An improved understanding of T cell immunity directed toward a model minor antigen may provide new approaches for preventing graft rejection.

Methods.

C57BL/6 (B6) recipient mice were engrafted with skin from B6 β-galactosidase transgenic (β-gal tg) donors and the induced T cell immune responses were characterized by cytokine ELISA spot assay. β-gal-specific immunity was manipulated prior to transplant through preinjection with β-gal in complete Freund's adjuvant (CFA) or through preinjection with soluble β-gal iv

Results.

B6 mice rejected β-gal tg skin by day 25. Rejection was associated with a low frequency of predominantly CD8+, interferon-γ-producing T cells capable of directly recognizing both β-gal tg cells and an immunodominant major histocompatibility complex I-restricted peptide derived from the β-gal protein. Rejection of multiple minor antigen disparate skin and major histocompatibility complex-disparate skin occurred significantly faster, and was associated with a 10-to 30-fold higher frequency of alloreactive T cells, than rejection of β-gal tg skin. Prepriming of recipients with β-gal in complete Freund's adjuvant resulted in an increased frequency of β-gal-specific T cells and accelerated rejection of β-gal tg skin. Intravenous injection of soluble β-gal-induced graft tolerance and a lack of detectable β-gal-specific immunity.

Conclusions.

The findings reveal that transgenically expressed β-gal behaves as a minor transplantation antigen and that manipulation of the β-gal-specific T cell repertoire can dramatically affect rejection of β-gal tg skin grafts. The work provides the foundation for mechanistic studies of tolerogenesis to minor antigenic determinants.