Cytomegalovirus complement-fixing IgM antibody.

Cytomegalovirus (CMV)-specific IgM that fixes complement in the presence of CMV antigen was demonstrated in sera from five patients with primary CMV infection. The CF reaction, demonstrable in the IgM fractions of the sera, was not affected significantly by absorption with aggregated IgG but was abolished by treatment with 2-mercaptoethanol. The IgM antibody was readily detected in CF tests with crude cell-extract antigens, prepared from CMV-infected tissue culture cells, or with purified enveloped-virion antigen but not with CMV-soluble antigens.