Evaluation of accessory cell heterogeneity. II. Failure of dendritic cells to activate antigen-specific T helper cells to soluble antigens

Abstract

The activation of antigen‐specific T cells requires Ia⁺, antigen‐presenting accessory cells (AC). Dendritic cells (DC) and macrophages (Mϕ) isolated from spleen and peritoneal exudate were tested as AC for the activation of T helper cells and the induction of T cell proliferation. The cell separations to obtain DC and splenic Mϕ were performed by discontinuous bovine serum albumin gradients, adherence on petri dishes and rosetting with opsonized sheep erythrocytes. DC as well as the Mϕ were able to induce antigen‐specific T cell proliferation, but only the Mϕ and not the DC activated antigen‐specific T helper cells which help B cells for antibody production to soluble antigens. Keyhole limpet hemocyanin‐specific T cells repeatedly stimulated with DC and antigen also did not express helper activity. The failure of DC to induce T helper cells was not due to the activation of a suppressor pathway. Thus, dendritic cells, although very efficient as AC in the induction of various T cell functions, are not able to activate T helper cells required for carrier‐specific T‐B cooperation and therefore cannot be the sole accessory cells. Based on these results and on previous data using Ia⁺ tumor cell line as AC, we confirm the existence of functional AC heterogeneity.