The distribution of Ia antigens was studied in murine spleen lymphocytes by an ultrastructural technique employing deep freeze etched replicas. Ia antigens were labeled on cells from appropriate congenic and recombinant strains of mice by incubating the cells with FITC conjugated anti Ia(k) antibody, followed by ferritin coupled Fab anti FITC. Ia antigens were detected predominantly on immunoglobulin (Ig) bearing B lymphocytes. Antigens coded for by the entire I(k) region were present on the surfaces of 95% of the positive cells (from B10.BR mice) in densely packed microclusters. Ia specificities coded for by the I A and I C subregions (on 4R and B10.HTT mice) exhibited a more variable pattern with 30 to 35% of the labeled cells having sparsely distributed Ia antigens in relatively discrete microclusters. Binding of anti Ia(k) antibody at 37°C led to patch formation but not to capping. Modulation of surface Ig left Ia antigens diffusely distributed on the cell surface, indicating that these two membranes proteins are independent molecules.
|Number of pages||8|
|Journal||Journal of Immunology|
|State||Published - Dec 1 1976|