Two T-cell populations mediate delayed-type hypersensitivity to murine influenza virus infection

Two classes of T lymphocytes can mediate delayed-type hypersensitivity (DTH) to influenza virus in the mouse. If non-infectious virus preparations are used to sensitize for or to elicit a DTH response, the effector cells are found to be Ly-1-positive and are I-region-restricted. If infectious virus is used both to sensitize for and to elicit the reaction, a second set of effector cells is also directed, which are Ly-2,3-positive and are D- or K,D-region-restricted. The latter cells are cross-reactive within the A strains of influenza viruses, and pretreatment of the mice with high doses of cyclophosphamide markedly decreases their generation in the spleens of sensitized mice, suggesting that the cells that demonstrate DTH activity in vivo may also have cytotoxic activity in vitro.