The capacity of antigen-presenting cells is fully preserved in childhood cancer patients.

T cells from 19 out of 25 childhood cancer patients showed impaired proliferative responses to purified protein derivatives (PPD)-pulsed antigen-presenting cells (APC) although all of the patients had been immunized with BCG. To test whether such low responsiveness of T cells results from the dysfunction of T cells or from that of APC, the experiment was designed to assess the proliferative response of T cells from patients or their parents to PPD-pulsed APC from patients or parents. These combinations seem to be suitable to assess the activity of T cells or APC since at least partial identity of HLA-D/DR antigens is required for T cell-APC interactions. Although T cells from patients who showed low responsiveness to PPD failed to respond even to PPD-pulsed APC from parents, T cells from parents were able to respond to PPD-pulsed APC from patients as well as to autologous APC. These observations strongly suggest that the low responsiveness to PPD in childhood cancer patients results from the dysfunction of T cells, and the capacity of APC is fully preserved. In other words, it appears that the capacity of APC is not impaired by chemotherapy, neoplastic cells, or other factors. Suppressor T cells appeared not to be involved in such dysfunction of T cells.