A comparison between Fc receptors for IgG1 and IgG3 on human monocytes and lymphocytes using anti-Rh antibodies.

In a rosette assay with human erythrocytes equally sensitized with anti-Rh antibodies, the Fc receptor-bearing (FcR) cells are much more numerous among monocytes than among lymphocytes. FcR monocytes could be detected using IgG1 and/or IgG3 antibodies although a higher percentage of FcR cells is observed with sera containing IgG3. FcR lymphocytes are detectable almost only with sera containing IgG3 antibodies. If the anti-Rh antibodies are restricted to IgG1 none or single FcR cells could be found. The application of mixed rosette assay with fluorescein-stained erythrocytes sensitized with IgG3 and unstained red cells sensitized with IgG1 allowed documentation of the presence of receptors for both subclasses on monocytes as well as on lymphocytes although some differences between these cells were observed. Almost all FcR monocytes bind both IgG subclasses, although in different proportions. On the contrary, most FcR lymphocytes bind only or mainly IgG3, but receptors for IgG1 can also be detected.