Fc Receptors for IgG₁ and IgG₃ on Human Mononudear Cells ‐An Evaluation with Known Levels of Erythrocyte‐Bound IgG

Abstract

Abstract. The Fc receptors on mononuclear cells were investigated by a rosette technique in which human erythrocytes were sensitized with a known number of molecules of anti‐Rh antibodies (IgG 1 or IgG 3 ). The number of IgG molecules was quantitated by a radiometric antiglobulin test. The present quantitative evaluation reveals that (1) there is a logarithmic relationship between the proportion of rosettes and the amount of erythrocyte‐bound immu‐noglobulin for both types of mononuclear cells, and for both subclasses; (2) similar percentage of rosettes can be obtained with fewer IgG 3 than IgG 1 molecules (about 1:4); (3) for a given number of erythrocyte‐bound immuno‐globulins a higher percentage of rosettes is observed with monocytes than with lymphocytes (ratios of about 3:1 for IgG 1 and 5:1 for IgG 3 ); (4) the minimum number of IgG 3 molecules for adherence is 180–460 for monocytes, 520‐1,300 for lymphocytes, whilst for IgG 1 the numbers are 1,180‐4,300 for monocytes and 3,400‐14,200 for lymphocytes; (5) the minimum levels of sensitization by alloantibodies for adherence should be detectable by the antiglobulin test.