In vitro lymphocytes stimulation with scarlet fever toxin.

Rabbit peripheral blood, spleen and thymus lymphocytes were stimulated in vitro with scarlet fever toxin. The ultrastructure of stimulated blast cells was described; the morphological features of these cells are similar to those of T-lymphoblasts. 3H-thymidine incorporation into lymphocytes stimulated with ET or PHA was studied in correlation with blast formation. Some quantitative discrepancies between both parameters are discussed.