Tuberculin purified protein derivative-reactive T cells in cord blood lymphocytes.

Lymphocytes obtained from cord blood of newborn babies who were born of healthy mothers were studied in vitro for their responsiveness to purified protein derivative (PPD) of tuberculin. Cord blood lymphocytes proliferated in vitro by stimulation with PPD, despite wide variations in the results. Studies with fractionated lymphocytes revealed that PPD-responding cells belonged to E-rosetting, nylon wool-nonadherent T lymphocytes. Non-E-rosetting B lymphocytes alone did not proliferate at all after stimulation with PPD. In addition, bromodeoxyuridine and light treatment of in vitro PPD-stimulated lymphocytes eliminated the responsiveness to PPD. These results suggest that T lymphocytes do exist in cord blood and respond in vitro to stimulation with PPD. A possible role for PPD-reactive T lymphocytes in cell-mediated protective immunity in newborns is discussed.