FUNCTIONAL EXPRESSION AND RECOGNITION OF NONCLASSICAL MHC CLASS-I T10(B) IS NOT PEPTIDE-DEPENDENT

Studies of classical and nonclassical MHC class I molecules have shown that unique peptides are associated and functionally recognized by al loreactive T cells. We have recently shown that an alloreactive TCR-ga mma delta cell recognizes a nonclassical MHC molecule, T10(b). However , T cell recognition of this glycoprotein did not appear to require ty pical peptide recognition based on studies using transporter-defective mutant cell lines. In the current study, we have analyzed in detail, the role of peptide in T10(b) expression and recognition. The findings reveal that the recognition of the nonclassical MHC molecule by TCR-g amma delta cells is independent of species, tissue type, both the clas s I and class II Ag processing and presentation pathways, or the prese nce of peptides. In fact, biochemical analysis of the T10(b) chimeric molecule, T10(b)/L(d), transfected into CHO cells using radiolabeled [ H-3]leucine, HPLC, and mass spectrometry suggest that peptides are not associated with this nonclassical class I molecule. Therefore, some c lass I molecules, e.g., T10(b), do not associate with polymorphic pept ides typical of classical MHC class I molecules and can be expressed i n the absence of peptides on the cell surface in a functionally active form.