Antibody production and DNA synthesis of human lymphocyte subpopulations induced by PPD tuberculin.

Purified protein derivative (PPD) of tuberculin was found to induce antibody secretion and DNA synthesis in human lymphocytes from blood, spleen, tonsil and lymph node. Antibody secretion was measured as plaque-forming cells (PFC) against fluorescein isothiocyanate (FITC) coupled sheep red blood cells (SRBC) in a haemolysis-in-gel assay. Peak antibody secretion by 100 micrograms/ml of PPD was usually seen on day 6 for blood lymphocytes, and varied from day 3 to day 6 for spleen cells. Peak DNA synthesis for blood lymphocytes stimulated by various concentrations of PPD ranged from day 4 to day 7. The highest number of PFC in tonsil and spleen cells was induced by PPD compared to Staphylococcus aureus bacteria Cowan 1, lipopolysaccharide (LPS) and pokeweed mitogen (PWM). Antibody secretion by PPD was not affected when phagocytic cells were removed by iron treatment. PPD stimulated a higher DNA synthesis in unseparated lymphocytes or mixtures of T and B cells than in enriched T or B cell suspensions. PPD did not induce PFC in B cells enriched by the removal of sheep erythrocyte rosette-forming cells (E-RFC). However, more PFC were stimulated by PPD in enriched E-RFC compared to unseparated lymphocytes, which may indicate that most of the FITC-SRBC reactive B cells also form rosettes with SRBC.