Influence of dendritic cells on the in vitro allogeneic cytotoxic reaction of lymphoid cells derived from normal or Listeria innocua-infected BALB/c mice.

The role of lymphoid dendritic cells (DCs) in the development of an allogeneic cytotoxic reaction in vitro was examined. The T+B and T cell subsets originating from the spleens or lymph nodes of normal and Listeria innocua-infected BALB/c mice were used as the effector cells. Their cytotoxicity to 51Cr-labeled C3H fibroblasts was determined after removal of DCs and replacing them again. Moreover, the influence of exogenous mrIL-12 on the potency of DCs in the allogeneic reaction developed in vitro was checked. It was found that the DC-deprived T+B or T subsets of splenocytes, regardless of their origin, exhibited 27-38% lower cytotoxicity than those accompanied by natural DCs. The cytotoxicity of these subsets from normal lymph nodes decreased by 22%, while the activity of bacteria-primed cells dropped by 38%. Replenishing effector cells with isolated DCs restored their cytotoxicity. Pulsation of normal DCs with IL-12 had no effect on the recovery of normal cell cytotoxicity. However, the IL-12-pulsed DCs were able to intensify the cytotoxicity of T+B subsets derived from the spleens or lymph nodes of L. innocua-infected mice. The results suggest that the alloantigen presentation by DCs to cytotoxic lymphocytes also takes place in the reaction developed in vitro, regardless of effector cell origin.