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Erythrocytes, serum, and blood monocytes from patients with erythrocyte autoantibodies were examined by in vitro serologic and cell culture procedures in order to evaluate factors modulating patient mononuclear phagocyte activity. Monocyte recognition of autoantibody-coated erythrocytes was influenced both by antibody titer score and by the monocyte source. The results suggest that patients with low serum autoantibody titer scores and normal monocyte behavior are less likely to destroy autologous or normal donor erythrocytes than are patients with high-serum antibody titer scores or enhanced monocyte activity. We conclude that patient, rather than normal donor monocytes, must be used in cellular assays designed to predict the fate of erythrocytes transfused into patients with erythrocyte autoantibodies.

Three assay systems-EAIgG rosette formation, 51Cr release, and erythrophagocytosis-were used to quantitate interaction between antibody-coated human erythrocytes and normal blood monocytes. The three methods were compared in terms of time requirements and sensitivity. Erythrophagocytosis required more time to perform (2 hours) than did rosette tests (30 minutes) but less than minimum 51Cr release assays (5.5 hours). Erythrophagocytosis was 20-fold more sensitive than either of the other two procedures. Results obtained with purified IgG anti-D and with antibodies induced by transfusion or pregnancy were similar.