Abstract
An enzyme-linked immunosorbent assay using monoclonal antibodies was developed to study the subclass distribution of immunoglobulin G (IgG) to cytomegalovirus (CMV) in individuals from a number of clinical groups. Most CMV-seropositive individuals had IgG1 and IgG3. IgG2 and IgG4 were detected less frequently at very low levels of activity, mostly among mothers at delivery and renal patients. Most seroconversions were accompanied by an important increase of the IgG1 activity, whereas IgG3 appeared at lower levels; neither IgG2 nor IgG4 occurred. This suggests that these isotypes play a secondary role in the response to the CMV infection and that they may be considered markers of past infections. Anti-CMV IgG1 is the most efficiently transmitted through the placenta. Whether infected or not, newborns had the same subclass distribution and activity levels as their mothers. Isotype determination did not offer a decisive explanation of a number of discrepancies observed between CMV IgG enzyme-linked immunosorbent assay and complement fixation test results.