Association between Ia antigens and the Fc receptors of certain T lymphocytes

The Fc receptors of thymic and splenic T lymphocytes were detected using indirect immunofluorescence and soluble antigen-antibody complexes. 10-20% of thymocytes and 40-50% of Thy-1-positive splenic lymphocytes bound antigen-complexed Ig. The binding to thymocytes was partially inhibited (45-74%) by antibodies against antigens determined by the I region of the H-2 complex, but not by antibodies against K- or D-region antigens or Thy-1 antigen. The inhibition did not require the Fc portion of the inhibiting antibody. These results provide evidence that Ia antigens and the Fc receptors of some T lymphocytes are associated, and that the populations of T cells which bear these moieties at least partially overlap.