IgM antibodies to red cells and autoimmune anemia in patients with malaria *

Abstract

Rising titers of IgM antibodies to red blood cells were found in 56 patients following infection with Plasmodium falciparum parasites. These antibodies, detected by indirect immunofluorescence using fluorescein-conjugated monospecific antisera, were not present in the sera of 23 non-malaria patients with high IgM concentration, 9 patients with infectious, malignant, and autoimmune diseases, and 16 normal subjects. Rising titers of IgM erythrocyte antibodies were associated with an increase of mean IgM from 100 to 500 mg/100 ml and a decrease of mean C3 from 150 to 75 mg/lOO ml over 24 days. Mean concentrations of serum IgA, IgG, IgD, IgE, albumin, globulin, and total protein were not significantly different in patients and controls throughout the study. IgM erythrocyte antibody titers and serum IgM levels were highest, and serum C3 were lowest in the most anemic patients. Survival time of 51Cr-tagged normal red cells was reduced in 10 of 11 patients studied following the clearance of malarial parasitemia and was the shortest in the most anemic patients.