Cells involved in DH response in mice were investigated by footpad assay in sensitized mice with methylated human serum albumin (MHSA) and complete Freund's adjuvant (CFA). Lymphoid cells responsible for eliciting footpad swelling in sensitized mice are sensitive to ATS and relatively resistant to radiation, and ferritin, macrophage toxic agent, completely suppressed eliciting footpad swelling. However, ATS administration to mice before sensitization failed to effectively suppress induction of DH to MHSA in mice. It was also confirmed by means of cell transfer experiment in adult thymectomized and lethally irradiated recipients that cells triggering delayed skin response are θ-positive T cells.
Reconstitutive capacity of various individual and mixed lymphoid cell populations to induce DH response in thymectomized and lethally irradiated mice was examined using dose response studies, to elucidate the role of cells involved in establishment of DH state to MHSA. A good correlation between the transferred thymus or spleen cell dosages and the degree of FPR in the recipients was seen. On the other hand, injection of anti-θ treated bone marrow cells to mice given moderate doses of thymus cells did not affect the degree of FPR within a wide range of bone marrow cell doses. Thus, DH response to MHSA in mice requires the cooperation of both thymus and bone marrow cell populations. However, as T cells are limiting cells determining the degree of the sensitive state of DH, such may reflect the reactivity of sensitized T cells producing DH lesion in the skin. DH in mice is a highly T-dependent immune phenomenon both in afferent and efferent limbs.