Effects of antibiotics on the developing immune system.

A combination of penicillin and cloxacillin (Ampiclox, Beecham Research Laboratories) is indicated for prophylaxis and treatment of bacterial infections in premature babies or neonates. We studied the functional development of the immune system in the offspring of female ICR mice administered Ampiclox on days 13-16 of pregnancy in clinically relevant doses. Immune functions were assayed after immunization with sheep red blood cells in the 5th and 10th postnatal week. Changes of hemagglutinin antibodies, delayed-type hypersensitivity and proliferative responses of spleen lymphocytes and thymocytes were observed. Ampiclox influenced humoral immunity also when administered directly to rat young on postnatal days 9-11 or 14-16. Although the clinical relevance of our experimental data remains to be established an increased sensitivity of the developing immune system to immunomodulatory effects should be considered also in the context of antimicrobial therapy. (Fig. 6, Ref. 27.)