Functional maturity of cord blood B lymphocytes: Staphylococcus aureus Cowan 1 induces IgG secretion in the human neonate.

Lymphocytes from newborn infants and adults were investigated with the polyclonal B cell activators Staphylococcus aureus Cowan 1, soluble protein A, and pokeweed mitogen (PWM). In cord blood lymphocytes (CBL), protein A and PWM induced only meagre IgM responses, whereas Cowan 1 bacteria induced synthesis of both IgM and IgG in quantities comparable to adult levels. We were also able to establish the neonatal origin of the Ig producing cells. Thus, cord blood lymphocytes seem to be functionally mature enough to produce any Ig class, provided they are given the right stimulus.