Mitogen-induced multiplication of lymphocytes from newborn infants.

Marked lymphocyte responses to PHA, ConA and PWM were demonstrated in the first week of life. Prematurity up to 30 weeks gestational age did not influence the results. There were only small variations in the responses from day to day, no sex differences, and no differences between infants who were small for gestational age of appropriate weight. Newborn infants with high serum IgM-concentrations had reduced lymphocyte responses to ConA, possibly through the influence of ConA on B-lymphocytes. Infants of mothers who had received corticosteroids prior to delivery had lower mean responses to all 3 mitogens, but the differences between the steroid- and comparable non-steroid groups were not significant. The results suggest that newborn infants have functioning cellular immune mechanisms.