Systemic antibody deficiency in patients without serum immunoglobulin deficiency or with selective IgA deficiency

Serum IgG tetanus toxoid antibody (IgGTTab) concentrations were measured in patients with chronic chest infections or recurrent acute chest infections following immunization and compared with results obtained in a group of 43 controls. Apart from selective IgA deficiency in some patients, all had normal or high serum immunoglobulins. Using an enzyme linked immunosorbent assay (ELISA) for IgG TTab, antibody was present following one immunization in all controls who had previously been immunized and following two immunizations in those not previously immunized. Ninety-seven and a half per cent of controls had a serum antibody concentration of greater than 4 micrograms/ml. Following the same immunization schedule, eight of 45 (18%) patients with chronic chest infections and three of 11 (27%) patients with recurrent acute infections had a serum IgG TTab of less than 4 micrograms/ml. The three patients with a low IgG TTab concentration and recurrent acute infections all had selective IgA deficiency. Two of these patients have benefited from injections of normal human immunoglobulin. It is suggested that systemic antibody deficiency as a cause of chronic or recurrent respiratory tract infections cannot be excluded by measuring serum immunoglobulin concentrations alone and that it is of value to measure antibody responses following immunization.