MACROPHAGE-T CELL-INTERACTIONS .2. UPTAKE BY T-CELLS OF FRAGMENTS BEARING LA-DETERMINANTS RELEASED FROM MACROPHAGES

An antibody binding assay was used to detect the presence of Ia antigens on splenic T cells of BALB/c mice. The binding of the anti-Ia antibody was determined by reverse immune cytoadherence which detects surface Ig in a highly sensitive and reproducible manner. By this approach Ia antigens could easily be detected on 10-12% of splenic T cells isolated by nylon wool columns. The Ia + T cells became Ia- upon culture in vitro for 4 hr but 70-80% of these cells were reconstituted following short exposure to a macrophage supernate. Such supernates contain Ia antigens as shown by binding to proper antisera as well as inhibition of cytotoxicity. Removal of Ia antigens from the supernate abolished its ability to reconstitute the Ia + T cells. Removal of the Fc receptors known to be present in these supernates did not affect the ability of the supernates to reconstitute the Ia antigens on T cells. The size of the Ia antigens was estimated as less than 10,000 daltons. The Ia antigens are carried on the Fc + T cells. These data indicate that the subpopulation of Fc + T cells acquires fragments of Ia antigens released from macrophages. © 1979.