Separation of T cell subpopulations capable of DNA synthesis, lymphotoxin release, and regulation of antigen and phytohemagglutinin responses on the basis of density and adherence properties.

T memory cells specifically responsive to ovalbumin and performing the diverse functions of DNA synthesis, lymphotoxin release, and regulation can be isolated in enriched numbers in the most buoyant fractions (A+B) of bovine serum albumin gradients on day 9 after sensitization. At least 20-30% of these cells are capable of mounting a blastogenic response to ovalbumin. A+B cells responding to ovalbumin with DNA synthesis have adherent properties and are further enriched on passage through glass wool. The subpopulations capable of entering into blastogenesis and DNA synthesis and of lymphotoxin release are unresponsive to T mitogens. A+B cells are capable of either potentiating or suppressing DNA synthetic responses to both phytohemagglutinin and antigen when added to 5 X 10(5) D cells in different proportions. Potentiation or suppression of phytohemagglutinin responses were observed with 1 X 10(5) A+B cells, and total suppression was observed with A+B in the range of 4 X 10(3) to 2 X 10(4). The response to antigen was sometimes inhibited in the same cell combinations that gave a potentiated response to phytohemagglutinin and vice versa. Regulatory cells in this system were not macrophages since their effect was not mimicked by addition of peritoneal macrophages, and ablation of macrophages by carrageenan affected neither the potentiation nor suppression.