Discrepancy between Effects of in vivo and in vitro Administration of Gammaglobulin on Phagocytic Killing of <i>Streptococcus pneumonia</i><i>e</i> in an Antibody-Deficient Serum

Phagocytic killing of Streptococcus pneumoniae serotypes 6A, 14, 18C, 19F and 23F was investigated in the dysgammaglobulinemic serum of a patient with recurrent pneumococcal infections. Previous studies with this serum had established combined IgG2, IgG4 and IgA deficiency, deficiency with regard to specific antipolysaccharide antibodies and essentially normal complement functions. Phagocytic killing of all serotypes was reduced in the patient’s serum. Addition of immunoglobulin in vitro enhanced both classical and alternative complement pathway mediated opsonization. In constitution experiments neither purified Clq nor CRP influenced phagocytic killing. Surprisingly, intramuscular administration of a fairly small dose of gammaglobulin to the patient was associated with a rapid increase in the serum opsonic activity for serotype 23F. The increased opsonization occurred before specific anticapsular antibodies were detectable in serum. The findings suggest that the possible effects of gammaglobulin treatment may not exclusively be related to the acquisition of serotype-specific antibodies.