Induction of T-cell proliferation by an Ia+ monocytic tumor clone

Ia+ immature malignant monocyte clones were isolated from retrovirus-induced lymphomas. These lymphomas contained a predominant population of Ly-1+ T cells. In order to explain this anomaly, the functional capacity of one of these clones, ORA I-a, was assessed. The results indicated that ORA I-a could present protein antigen to syngeneic and semisyngeneic antigen-primed lymph node T cells. Allogeneic stimulation, however, could not be induced. Furthermore, ORA I-a-conditioned medium could augment mitogen-dependent and -independent thymocyte proliferation. These studies suggest that the unique populations of malignant antigen-presenting cells can interact with distinct T-cell subpopulations. Functional analyses of these tumor cell lines may thus be useful in elucidating some of the cellular interactions which occur during the course of immunity.