Increased half-life of gammaglobulin after prolonged intravenous replacement therapy.

The half-life of total IgG and antibodies to cytomegalovirus and pneumococcal polysaccharide type III was consistently prolonged after a 9 month course of intravenous gammaglobulin treatment in three patients with 'primary' hypogammaglobulinaemia. The half-life of antibody to tetanus toxoid showed no consistent pattern. These data are at variance with the traditional dogma that IgG half-life is inversely related to serum IgG concentration. They suggest that patients on intravenous gammaglobulin therapy are likely to need less, rather than more, infusions when their serum IgG has risen to within the physiological range.