Objective: The immunoglobulin G2 subclasses contain predominantly antipolysaccharide antibodies. It was therefore believed intuitively that low immunoglobulin G2 levels could predispose individuals to infections with encapsulated bacteria. Although many reports initially supported this notion, more recent studies challenged it. Regardless of the biological significance, the natural history of low immunoglobulin G2 levels has not been carefully studied.
Methods: We studied the outcome of low serum immunoglobulin G2 subclass levels in children. Thirteen patients who were referred because of recurrent infections were found to have low immunoglobulin G2 levels. Laboratory evaluation at presentation and follow-up visits included total serum immunoglobulins, immunoglobulin subclasses, and specific antibodies to protein antigens and to pneumococcal vaccine.
Results: Low immunoglobulin G2 levels resolved completely within 0.6 years to 6 years (median: 1.5 years) in all patients. All 13 patients responded adequately to vaccination with protein antigens such as tetanus toxoid and polio as well as to immunization with pneumococcal vaccine. Four of 13 patients had a previous history of transient hypogammaglobulinemia, raising the possibility that the other cases may simply represent the tail end of this condition.
Conclusion: We have demonstrated that low immunoglobulin G2 detected in early infancy and childhood is likely to resolve completely within several months and up to 6 years from the time of presentation.