Activation of lymphocytes by PPD and PHA is promoted by exudate from BCG-induced pleurisy.

Cell-free pleural exudate (PE) obtained from guinea pigs with BCG-induced pleurisy was tested for influence on in vitro activation of lymphocytes by PHA and PPD. A previous study has shown poor activation of lymphocytes derived from pleural exudate and this was thought possibly to depend on inhibitory activity of the exudate. Instead of the expected suppressive effect, however, PE in the present study promoted activation of lymphocytes from most sample sites in healthy and pleuritic guinea pigs. Thus, in the presence of PE, lymphocytes derived from the pleural exudate were always activated in vitro by PHA and PPD.