Lymphocyte transformation and the number of antigen-responsive cells in humans.

The lymphocyte transformation response of normal human subjects to the antigen streptokinase/streptodornase (SK/SD) was analyzed by quantitating antigen-responsive cells (ARC), estimating the first generation lymphocyte response (FGLR), and performing standard lymphocyte transformation assays at different time points. Unlike the results obtained with the nonspecific mitogen phytohemagglutinin (PHA), the response to SK/SD appeared to depend almost entirely on the participation of progeny lymphocytes derived from a small number (mean of 21.3 +/- 5.8 per 100,000 mononuclear cells) of cells initially sensitive to the antigen. Similar peak lymphocyte transformation responses were obtained for the 2 stimuli, although those to SK/SD occurred later. Lymphocyte transformation data obtained after a shorter than optimal culture period (6 days) appeared to be a better estimate of ARC than the data obtained at the peak of the response of ARC than the data obtained at the peak of the responses did. However, ARC were best estimated by determining the FGLR or the number of days required for the lymphocyte transformation response to reach its peak.