H-2-dependent cell-mediated immunity in vivo: delayed-type hypersensitivity and contact sensitization induced by fluorescein isothiocyanate-conjugated cells

Fluorescein isothiocyanate (FITC) was found to be a suitable hapten to study cell-mediated immunity in vivo in mice. Delayed-type hypersensitivity (DTH) footpad swelling reactions were induced and elicited by injection of FITC-conjugated syngeneic spleen cells, and contact sensitivity (CS) was induced and elicited by skin painting with reactive FITC. Cross-reactive specificity between DTH and CS was demonstrated. Thus, DTH induction with FITC-spleen cells (FITC-SC) also led to the ability to elicit CS; and CS induction by skin painting also led to the ability to elicit DTH with FITC-SC. However, the 2 reactions differed in that the ability to elicit DTH induced by subcutaneous immunization with FITC-SC was evanescent, whereas CS induced by skin painting was long lived. Specificity of these reactions was hapten dependent and additionally required homology at the H-2 locus of the major histocompatibility complex. The H-2 specificity requirement was not evanescent.