Analysis of dendritic-cell-induced primary T-cell responses between HLA genotypically identical individuals.

DCs are known for their superior antigen-processing and antigen-presenting capacities. They are capable of processing intact protein: either endocytosed exogenous proteins or newly synthesized endogenous viral and bacterial proteins. They are potent inducers of primary T-cell immune responses such as in allogeneic MLRs. It is also known that DCs can provide a strong stimulus for autologous T-cell proliferation. So far no information exists on the capacity of DCs to induce primary mH antigen-specific T-cell responses. Therefore, we investigated whether human DCs, isolated from peripheral blood, were able to generate specific T-cell responses between MLR-negative HLA genotypically identical individuals in vitro. To this end, unfractionated cells, monocytes, and B cells were assayed in parallel with DCs to compare their capacity to activate unprimed T cells in a primary MLR. DCs indeed induced significant proliferation between HLA genotypically identical siblings, whereas the other APCs were unable to evoke any T-cell response at all. As expected, besides these allogeneic T-cell responses, autologous T-cell responses were initiated by the DCs as well. Nonetheless, despite further detailed analyses of the responding T cells, neither proliferative nor cytotoxic mH antigen-specific reactivities could yet be detected using the stimulation protocols described herein.