Identification of Ia antigens on the murine adenocarcinoma LT-85.

Antigens associated with the H-2Kk and I-Ak regions of the major histocompatibility complex have been identified with monoclonal antibodies on an in vivo grown murine alveologenic adenocarcinoma, LT-85. Immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis demonstrated differences in the molecular structure of I-Ak region-coded antigens between LT-85 and host C3H/HeN mammary tumor virus-negative (MTV-) or autologous C3HfB/HeN splenocytes. Ia antigens derived from LT-85 tumor cells exhibited both an increased heterogeneity in the alpha-chain and a lower apparent molecular weight in the beta-chain. Tryptic peptide mapping of the I-Ak antigen alpha- and beta-chains derived from C3H/HeN MTV- mice and LT-85 tumor cells revealed a single peptide difference in the beta-chains of these antigens. Results obtained with neuraminidase-treated I-Ak beta-chains indicated that this difference was not due to sialic and content. Maintenance of LT-85 in vitro, even for short periods, resulted in the loss of these I-Ak antigens. However, this loss of I-Ak antigen expression was fully reversible with in vivo growth.