An Incomplete Cold‐Reactive γG Antibody with i Specificity in Infectious Mononucleosis¹

Abstract

Summary. A new cold reactive antibody directed against fetal (i) cells is described in 90% of patients with infectious mononucleosis. It appears to be the 7S counterpart of the previously described 19S anti‐i antibody. The 7S anti‐i antibody interacts with a 19S anti γ globulin and the combination is responsible for the majority of the cold agglutinin phenomena previously shown in this disorder. The highest titers were detected in patients with severe hemolytic anemia, leukopenia, thrombocytopenia or combinations thereof.

Fatal Autoimmune Hemolytic Anemia Due to Immunoglobulin G Autoantibody Exacerbated by Epstein-Barr Virus

“…In about 25% to 50% of patients with EBV infection, hematologic complications of AIHA are generally mild. 17 We report the first case, to our knowledge, of a fatal IgG warm AIHA probably exacerbated by a coexisting EBV infection; we believe this case represents a reactivation of a latent EBV infection. The presence of a warm autoantibody in our patient is unique since EBV infection is typically associated with cold autoantibodies.…”

“…The mechanism by which infectious mononucleosis precipitates hemolytic anemia is obscure; however, one theory suggests that complexes of IgG and IgM bind to the RBC membranes, activate complement, and trigger hemolysis. 17 Colloquially, the frequency of clinically significant hemolysis in EBV infections is estimated to be low, and most of these cases are associated with cold agglutinins. The cold-agglutinin test result was negative in our patient.…”

The Clinical Pictures of Autoimmune Hemolytic Anemia

“…In hemolytic anemia of infectious mononucleosis, in addition to the usual IgM anti-i cold agglutinins, in some cases cold-reactive nonagglutinating IgG anti-i antibodies occur in concert with IgM cold-reactive anti-IgG antibodies (‘rheumatoid factors'). The latter may then cross-link the IgG-coated RBCs to produce agglutination [ 46 ].…”