Autoimmune Hemolytic Anemia Associated with an IgG Cold Incomplete Antibody1

Abstract

Abstract. Serologic studies are reported on a patient with severe autoimmune hemolytic anemia, whose red cells were strongly coated with IgG and with α2D component of C3. Direct and indirect Donath‐Landsteiner reactions were negative. In addition to a typical IgM anti‐I cold agglutinin of modest titer, the serum contained a lambda IgG incomplete antibody which bound more strongly to normal red cells at 4°C (1/64) than at 37°C (1/4). The IgG antibody did not require complement for binding but could bind complement and cause hemolysis with papainized red cells. Once bound, the IgG antibody did not dissociate appreciably at room temperature. The antibody eluted poorly from the patient's cells at 56°C but was readily dissociable from cell stroma at pH 3.5. The eluate exhibited no blood group specificity with a diagnostic red cell panel. In particular, equally strong reactions were obtained with O, A2, B, A1B, P + P1‐negative, Rh‐null, adult and cord red cells. Reactivity was not impaired by prior papainization of the cells. Although the patient improved following splenectomy, neither IgG nor IgM antibodies were detectable in a concentrated splenic extract. The properties of the present cold IgG incomplete antibody are compared with those previously reported; possible clinical implications of these antibodies are briefly discussed.