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LAH #133 - Ia Antigens on FcR positive T Lymphocytes

For the past several years, we have been using fluoresceinated antigen-antibody complexes (F*AgAb) to distinguish two distinct subpopulations of peripheral T cells — Fc receptor positive (FcR+) and Fc receptor negative (FcR-) T cells (1). Functional studies on populations of FcR- and FcR+ cells, purified on the fluorescence-activated cell sorter (FACS), revealed that the FcR- T cell subpopulation a) responded poorly, if at all, to concanavalin A (con A) in the absence of FcR+ T cells (2), b) contained the precursors of cytotoxic effectors of cell mediated lymphocytic (CML) responses (3) and c0 contained the helped T cells (1) but not the CML amplifier T cells (3). In contrast, the FcR+ T cell subpopulation a) was responsive to con A (2), b) contained the differentiated cytotoxic effector cells of CML responses (3), and c) contained the CML amplifier T cells (3) but not the helper T cells (1). Both FcR- and FcR+ T cells were capable of proliferating in mixed lymphocyte cultures upon exposure to allogeneic lymphocytes (3). Despite these functional distinctions between T cells bearing or lacking a detectable Fc receptor, the functional significance of the Fc receptor remained unclear.

An association of the Fc receptor on murine B lymphocytes and alloantigens controlled by loci mapping in the I-region of the H-2 complex (I-region associated or Ia antigens) has been reported (4, 5). This association was based on the observation that anti-Ia antibodies specifically inhibit the binding of aggregated immunoglobulin or antigen-antibody complexes to the Fc receptors of B cells. Recently, Ia antigens have been detected on at least a subpopulation of T cells (6-10). To determine whether the Ia antigens are expressed on the FcR+ T cells, we examined the ability of specific anti-Ia antisera to inhibit the binding of AgAb to the Fc receptor of splenic T lymphocytes.

R. D. Stout
D. B. Murphy
H. O. McDevitt
Leonard A. Herzenberg
Academic Press
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