SUBPOPULATIONS OF CD8+ CYTOTOXIC T-CELL PRECURSORS COLLABORATE IN THE ABSENCE OF CONVENTIONAL CD4+ HELPER T-CELLS

Four different subpopulations (Ly6C(neg), Ly6C(low), Ly6C(int), and Ly6C(hi)) of CD8+ T cells were arbitrarily defined on the basis of differential expression of Ly6C Ag. By combining the processes of electronic cell sorting and automated cell deposition, small numbers of respective CD8+ T cell subpopulations were directly deposited into tissue culture wells in which mitogen-stimulated responses were studied. Anti-CD3-stimulated proliferation and IL-2 production were the strongest by Ly6C(neg)/Ly6C(low) T cells, moderate for Ly6C(int) T cells, and highly deficient for Ly6C(hi) T cells. The level of IL-2 production for Ly6C(neg) CD8+ T cells was comparable to that of conventional CD4+ Th cells. Allogeneic stimulator cells elicited a strong cytotoxic response by Ly6C(neg + low) but not Ly6C(hi) CD8+ T cells in the absence of added lymphokines. When IL-2 was supplied in excess, anti-CD3 induced comparable levels of cell proliferation and cytotoxic activity in Ly6C(neg), Ly6C(low), Ly6C(int), and Ly6C(hi) CD8+ T cells whereas alloantigen stimulated an approximate fivefold higher cytotoxic response by Ly6C(hi) than Ly6C(neg + low) CD8+ T cells. Stimulation of co-cultures of B10 (CD8b) Ly6C(neg + low) and congenic B10.CD8a Ly6C(hi) CD8+ T cells in the absence of added lymphokines, followed by selective elimination of activated CD8.1+ (CD8.2+) T cells by anti-CD8.1 (anti-CD8.2) + C treatment, allowed the demonstration that help provided by Ly6C(neg + low) T cells can be effectively used by both Ly6C(neg + low) and Ly6C(hi) T cells in anti-CD3 and alloantigen induced proliferative and cytotoxic responses, respectively.