IDENTIFICATION OF AN HLA-DQ6-DERIVED PEPTIDE RECOGNIZED BY MOUSE MHC CLASS-I H-2D(B)-RESTRICTED CD8(-CELLS IN HLA-DQ6 TRANSGENIC MICE() T)

CD8(+) T cells from C57BL/6(B6) mice show cytotoxicity to B cell blast s prepared from syngeneic transgenic mice expressing HLA-DQ6 molecules in a mouse MHC class I H-2D(b) restricted manner. Although these resu lts suggest that CD8(+) T cells recognize peptides derived from DQ6 mo lecule bound to H-2D(b) on target cells, no direct evidence so far has been obtained. To clarify this, we synthesized 23 peptides correspond ing to DQ6 alpha or beta chain and carrying the motifs of D-b-binding peptides, and examined their capacity to induce cytotoxicity in the CD 8(+) T cell line. We show here that DQA1-2, one of these peptides, ind uced cytotoxicity of the CD8(+) T cells when this peptide was pulsed t o H-2D(b) expressing target cells, as efficiently as HLA-DQ6 expressin g target cells did. Thus, our results suggest that DQA1-2 can be natur ally processed from DQ6 molecules and recognized by the CD8(+) T cells in the context of H-2D(b) molecules. These results suggest that allog eneic HLA class II molecules are involved in the rejection not only as the ligand for T cell receptor of alloreactive CD4(+) T cells but als o as self-peptides bound to HLA class I molecules recognized by CD8(+) T cells.