Immunoglobulin G subclass responses to cytomegalovirus in seropositive patients after transfusion

The immunoglobulin G subclass responses to cytomegalovirus (CMV) after red cell (RBC) transfusion were studied in 26 seropositive surgery patients and 34 transfused seropositive oncology patients. Also included as controls were 18 surgical patients who received no RBCs during surgery. None of the 78 patients studied had IgG2 to CMV before or after transfusion. The absence of a total IgG response to CMV after transfusion could not be attributed to preexisting deficiencies in one or more subclasses, because all 78 patients had similar levels of IgG1, IgG3, and IgG4 to CMV before transfusion. Discriminant analysis was used for statistical evaluation of the combined CMV subclass responses in each patient and the individual subclass responses. Individual patients responded to CMV antigens with an increase in concentration in any of the three subclasses or any combination of the subclasses, excluding IgG2. IgG subclass analysis showed that 10 of 27 patients who did not respond with at least a fourfold total IgG titer rise had a significant increase in IgG subclass antibodies to CMV. Three of 33 patients with at least a fourfold total IgG titer rise lacked a subclass response. These results suggest that the measurement of IgG subclasses may be a sensitive indicator of immune response to CMV.