The lymphocyte transformation response of fetal hemolymphatic tissue to mitogens and antigens.

Lymphocyte transformation responses to three different mitogens (phytohemagglutinin (PHA), pokeweed mitogen (PWM), and concanavalin A (Con A)) as well as four antigens (streptolysin O (SLO), keyhole limpet hemocyanin (KLH), streptokinase-streptodornase (SKSD) and tuberculin purified protein derivative (PPD)) were studied ontogenetically in 30 human fetuses ranging in gestational age from 6-19 weeks. In most organs lymphocyte responsiveness to Con A in human fetuses seemingly develops in concert with responsiveness to PHA and PWM. One 19 week fetus had an apparent antigen specific response to SLO with stimulation of cord blood and bone marrow lymphocytes. The same fetus also had mitogen responsiveness in bone marrow.