Low molecular weight IgM in cytomegalovirus infections and cardiac patients.

When 71 ischaemic heart disease and cardiomyopathy patients' sera were examined by the IFA (indirect fluorescent antibody) test, 18 of the 49 (36%) with CMV (cytomegalovirus) CF antibody appeared to contain a specific LMW (7S approx) IGM. This IgM was unrelated to the presence of RF (rheumatoid factor) demonstrable by agglutination of IgG-coated latex and by an immunofluorescence test, was not absorbed by heat-aggregated IgG and latex, nor did its demonstration appear to be complement dependent. It was demonstrable in acute CMV infection and in some cardiac patients, binds to HSV (herpes simplex virus) and CMV-infected cells.