Syngeneic sensitization of mouse lymphocytes on monolayers of thyroid epithelial cells (TEC). VIII: Gamma interferon induced Ia antigen expression on TEC cultures.

We previously reported that the expression of Ia antigens on cultured monolayers of murine thyroid epithelial cells (TEC) occurred with a particular distribution exclusively on the basal part of the cultured thyroid cells, while class I antigens of the major histocompatibility complex (MHC) and thyroglobulin (Tg) are only detected on the apical surface. It appears that, 24 to 48 h after the deposition of syngeneic lymphocytes, Ia antigens are expressed on the apical side of cultured TEC, i.e. the surface that bears Tg and is in direct contact with the responder lymphocytes during syngeneic sensitization of T lymphocytes. We hypothesized that this phenomenon could represent, in syngeneic situations, the restriction process in antigen recognition by T cells, as demonstrated by I-A restricted primary syngeneic sensitization (PSS) on murine TEC. Moreover, we found that the addition of either PSS supernatants or gamma interferon (gamma IFN) to monolayers of TEC induced the expression of Ia antigens on the apical cell surface of these TEC cultures 24 to 48 h later. Taken together our data demonstrate that during the first hours of PSS, class II antigen and Tg are expressed on murine TEC cultures. This simultaneous expression of these antigens explains the strict in vitro I-A restricted PSS we previously observed.