Specific cytotoxicity of human lymphocyte subpopulations defined by bacterial adherence.

It has been shown that lymphocytes can be subdivided into subpopulations based on their binding of bacteria. Monolayers of immobilized and fixed bacteria were used here to separate T cells into BA-T1T2, adherent to Escherichia coli-2 (EC-2+) and BA-T3T4, non-adherent to this strain of bacteria (Ec-2-) (our denomination). The cells were activated in mixed lymphocyte cultures (MLC) and tested for cytotoxic activity. The BA-T1T2 cells developed the same cytotoxic activity as the sham-separated T cells whereas BA-T3T4 cells did not become cytotoxic. When the T cells were separated into BA-T2 cells, adherent to Bacillus globigii (Bg+), and BA-T1T3T4, non-adherent, (Bg- cells became cytotoxic. Since BA-T1 cells, which represent 10-20% of T cells, are common to the two populations they appear to contain all T cells needed to develop the specific cytotoxicity for allogeneic cells. When the cells were first activated in MLC for 6 days and then separated by adherence to E. coli-2 or B. globigii, all cytotoxic cells were in the non-adherent fraction. We concluded that the subpopulation of T cells which are Ec-2+Bg- (less than 20%) contain all the cells required for the development of cytoxic cell function and that after activation they become Ec-2-Bg-.