A Con A-stimulated T-cell hybridoma releases factors affecting haematopoietic colony-forming cells and B-cell antibody responses

Abstract

The major role of the thymus-dependent class of lymphocytes (T cells) seems to be regulatory. With the exception of cytotoxic T cells, T-cell subsets act by modulating the function of other T and B lymphocytes^1,2 and macrophages³, and also the progenitors of erythrocytes, monocytes and myeloid cells^4–7. Most of these regulatory effects are mediated by humoral factors, but despite convincing evidence that T cells are essential for the production of such factors, in many instances it has been difficult to demonstrate conclusively that the T cells actually synthesise the factors⁷. Factors stimulating the formation of myeloid colonies in agar can be produced by a T-cell lymphoma, EL4 (ref. 8), and by a hybridoma formed by the fusion of a T-cell lymphoma with pokeweed mitogen-stimulated spleen cells, although in this case it was not possible to demonstrate directly that the non-tumour parent had been a T cell⁹. Here we report that a cloned T-cell hybridoma can be induced to release factor(s) stimulating both the growth of haematopoietic colony-forming cells and the B-cell response to antigen. Incubation of the hybridoma with the T-cell mitogen concanavalin A (Con A), was required for the production of these activities, which were detectable 24 h after addition of the Con A. These activities were not produced when the parental tumour (BW5147) was incubated with Con A.