Abstract
s. The possibility that Ia antigens are unique among H-2 antigens in their relationship to the Fc receptor was investigated in an EA rosette assay. Antibody specific for antigens in various regions of the H-2 complex was incubated with mouse cells, and the ability of the cells to form rosettes with antibody-coated chicken erythrocytes was tested. Antibody raised against the H-2 antigens of Ia-negative tumor cells was highly effective in inhibiting rosette formation. A variety of antisera against K-, 1-, and D-region antigens tested in recombinant mice inhibited EA rosette formation, suggesting that antigens in each of these regions could be detected in rosette inhibition. The F(ab')2 fragments of all antisera tested also produced specific EA rosette inhibition. Finally, antibody against la antigens failed to inhibit bone marrow RFCs, although antibody against H-2 K and H-2D antigens did inhibit. Although H-2 serology is in a state of rapid change at present, it must be concluded that in this assay, antibody against antigens in the K and D regions as well as the 1 region can inhibit EA rosette formation. Inhibition of these rosettes by anti H-2 sera is therefore not due to a special association of Ia antigens with Fc receptors.
Highlights
The Fc receptor is a cell-surface component demonstrable on a wide variety of normal and neoplastic cells
The total dependence of the rosettes on Fc receptor binding was demonstrated as follows: (a) when the erythrocytes were coated with Rabbit antichicken antibody (RACA) from which Fc portions had been removed by pepsin-digestion, no rosettes were formed; (b) preincubation of the rosette-forming cells with nonrelevant immune complexes or with aggregated IgG inhibited EA rosette formation
Inhibition of an Fc receptor-dependent assay by antibody against the Fc receptor-bearing cells may be due to several potential mechanisms: (a) the antibody may be binding to the Fc receptor by its Fc portion; (b) the antibody may be producing membrane changes that could alter the ability of the Fc receptor to bind; (c) the antibody might bind to a site on the cell membrane remote from the Fc receptor, but might still be able to exert steric effects, in assays where the binding of large aggregates or erythrocytes was required; (d) the antibody might be binding directly to antigens intimately associated with the Fc receptor
Summary
The Fc receptor is a cell-surface component demonstrable on a wide variety of normal and neoplastic cells (for review see Kerbel and Davies 1974). It has potential significance in many immunologic phenomena, including cytotoxicity, allergy, regulation of the immune response, tolerance and enhancement, and others. It was shown that the F(ab')z of antibodies against Ia and other B-cell antigens inhibited rosette formation between antibody-coated erythrocytes (EA) and lymph node lymphocytes.
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