The elicitation in immunized mice of delayed-type hypersensitivity (DTH) responses to nickel sulfate (NiSO4) was found to be mediated by the sequential activities of two different antigen-specific Thy-1(+) cells. Early-acting (2-hr) NiSO4-specific, DTH-initiating cells were required for elicitation of subsequent 24-hr NiSO4-specific DTH and had an unusual phenotype for an antigen-specific cell (Thy-1(+), CD5(+), CD3(-), CD4(-), CD8(-) CD23(+), CD45RA(+) (B220(+)), IL-2R(-), IL-3R(+), sIg(-), MHC Class II-, Mel-14(-), CD44(+) (Pgp-1(+)), J11d(+) (HSA(+)), MAC-1(+), LFA-1, and Fc gamma II-R(+)). In contrast, the late-acting, NiSO4-specific DTH-effector T cells were: Thy-1(+), CD5(+), CD3(+), CD4(+), CD8(-), CD23(-), B220(-), IL-2R(+), IL-3R(-), sIg(-), MHC Class II-, Mel-14(+), CD44(-) (Pgp-1(-)), J11d(-) (HSA(-)), MAC-1(-), LFA-1(+), and Fc gamma II-R(-). Our results led us to surmise that the early-acting DTH-initiating cells were necessary to locally recruit the late-acting effector T cells. Relatively high doses of anti-B220 (CD45RA) and anti-CD23 (IgE Fc epsilon RII receptor) monoclonal antibodies were necessary to completely eliminate all DTH-initiating cells, and therefore completely block subsequent expression of some late NiSO4-specific DTH activity that was due to the late-acting DTH effector T cells. In addition, we found that mast cells were important for expression of early-acting, DTH-initiating cell activity in this NiSO4-specific, DTH system. This was probably due to the absence of mast cells in mast cell-deficient WBB6F(1)-W/W-v mice. Our results indicated that two different antigen-specific Thy-1(+) cells are necessary to elicit NiSO4-specific DTH in mice and that mast cells are necessary for expression of the early component that is due to early-acting, DTH-initiating cells. (C) 1995 Academic Press, Inc.
