T ransplantation of bone marrow and solid organs initiates a complex array of imm uno­logical responses in the recipient. A perfect m atch at both m ajor and m inor histo­ com patibility (H ) antigens is a very rare occurrence. Therefore, im m une system of the recipient is confronted with an array of foreign antigens in the form of M HC-encoded molecules and bound peptides. Study of renal allograft infiltrating lymphocytes (GIL) from biopsies of individuals undergoing acute cellular rejection indicate that the allograft response includes T cells that recognize tissue-specific antigens. In cases in which there are M H C mismatches between the recipients and the donor organ these antigens can be defined as alloantigenic MHC-derived tissue-specific peptides (Table 16.1). When there is a complete HLA match between donor and recipient both conventional and tissue-specific minor H antigens can be recognized. Tissue-specific antigens may also be in involved in autoimmune disease.