Influences of heat aggregated human IgG on the proliferation of mononuclear cells

It is believed that circulating immune complexes (IC) play pathogenic roles by affecting lymphocyte and/or monocyte function in type III allergy. We studied the influences of heat aggregated human IgG (AHG), as a model of IC, on the proliferation of mononuclear cells in respect of difference in the involved IgG subclasses. IgG 1 and IgG 2 subclass of AHG (AHG1, AHG 2) suppressed significantly the proliferation of mononuclear cells without mitogens. Proliferation of mononuclear cells stimulated by concanavalin A (Con A) was significantly suppressed not only by AHG 1 and AHG 2 but also by AHG 4. Flow cytometric analysis indicated that unstimulated lymphocytes or monocytes could bind more AHG 1 and AHG 2 than AHG 3 and AHG 4. Since results coincided with the results mentioned above, unstimulated mononuclear cell proliferation was suppressed through the binding of AHG on the surface of mononuclear cells. AHG suppression of mononuclear cells stimulated by Con A was effectively inhibited by an addition of indomethacin and/or catalase.These results indicated that prostaglandin and/or H2O2 might play an important role in inhibition of proliferation of mononuclear cells by AHG. Taken together, IC play a different role in immune network by affecting lymphocytes or monocytes according to difference in IgG subclasses.