Differential requirements for rabbit dendritic cells and macrophages in T lymphocyte proliferation induced by various mitogens.

Dendritic cells have been isolated from rabbit lymph nodes. Morphologically and phenotypically, they resemble dendritic cells from the mouse and rat. A comparison was made of the accessory cell function of dendritic cells and peritoneal macrophages in T-cell proliferation induced by phytohaemagglutinin (PHA) or Con A, or by a simultaneous treatment with the enzymes neuraminidase and galactose oxidase (NaGo). Dendritic cells seemed to be more effective than macrophages as accessory cells in these assays. However, macrophages suppress lymphocyte proliferation through the release of oxidating agents and production of prostaglandins. Elimination of this suppressive effect of the macrophages by addition of a combination of 2-mercaptoethanol (2-ME) and indomethacin in PHA-induced cell proliferation resulted in a much higher support by macrophages, giving results that were comparable to those obtained with dendritic cells, but in NaGo-induced proliferation, macrophages were still not as effective as dendritic cells in the presence of the drugs. Experiments in diffusion culture vessels and with interleukin-1-containing macrophage supernatants showed that support by accessory cells can be mediated by soluble factors in PHA-induced proliferation. In contrast, in NaGo-induced proliferation, lymphocytes and accessory cells have to interact directly.