EXPRESSION OF A SINGLE-CHAIN HLA CLASS-I MOLECULE IN A HUMAN CELL-LINE - PRESENTATION OF EXOGENOUS PEPTIDE AND PROCESSED ANTIGEN TO CYTOTOXIC T-LYMPHOCYTES

We have synthesized a recombinant gene encoding a single-chain HLA-A2/ beta(2)-microglobulin (beta(2)m) molecule by linking beta(2)m through its carboxyl terminus via a short peptide spacer to HLA-AZ (A0201). T his gene has been expressed in the beta(2)m-deficient colorectal tumor cell line DLD-1. Transfection of this cell with the single-chain cons truct was associated with conformationally correct cell surface expres sion of a class I molecule of appropriate molecular mass. The single-c hain HLA class I molecule presented either exogenously added peptide o r (after interferon-gamma treatment) endogenously processed antigen to an influenza A matrix-specific, HLA-A2-restricted cytotoxic T-lymphoc yte line. The need for interferon gamma for the processing and present ation of endogenous antigen suggests that DLD-1 has an antigen-process ing defect that can be up-regulated, a feature that may be found in ot her carcinomas. Our data indicate that single-chain HLA class I constr ucts can form functional class I molecules capable of presenting endog enously processed antigens. Such molecules should be of use for functi onal studies, as well as providing potential anticancer immunotherapeu tic agents or vaccines.