Activation of lymphocytes alters Fc receptor-beta 2-microglobulin interrelationship on the lymphocyte surface

The effect of anti-beta 2-microglobulin (anti-B2Mi) on the expression of Fc receptors (FcR) of human lymphocytes was compared on resting and activated cells. Previously we reported that anti-B2Mi induces a "co-shedding" of FcR with the beta 2-microglobulin (B2Mi)-anti-B2Mi complexes when used under the conditions where the redistribution of membrane molecules is allowed (Sármay et al., Cell. Immunol. 56, 452, 1980; Sármay et al. Immunology 36, 339, 1979). Furthermore our group also described two types of FcR-bearing cells, one which shed their FcR during a temperature shift from 4 to 37 degrees C (FcRI+ cells) and the other which has an immobile type FcR under the same circumstances (FcRI+ cells) (Sándor et al., Immunology 38, 553, 1979; Sármay et al., Immunology 34, 315, 1978). In this work we have characterized the FcR released from the membrane as a consequence of anti-B2Mi treatment. We have found that they are the mobile, FcRI type. It was proved that the shedding of this FcRI is a consequence of the anti-B2MI-induced transformation of FcRII into the FcRI form on the membrane of the antibody-treated lymphocytes. On the activated T cells, however, anti-B2Mi is incapable of inducing the same phenomenon in the early phase of activation. In contrast, FcR expression is blocked by anti-B2Mi treatment similarly to that on resting lymphocytes, on the surface of activated B cells, or on activated T cells in the later phases of activation.