Human spleen as a source of T cell growth factor.

Human spleen cells were tested for the ability to produce T cell growth factor (TCGF) upon stimulation with PHA. Quantitative analysis of the amounts of TCGF produced under optimal conditions indicated that supernatants obtained from spleen cell cultures were approximately five times more active than those derived from peripheral blood leucocytes (PBL). Moreover, in contrast to PBL, there was no significant difference in TCGF production between individual spleen cell populations. Among splenic T cells, TG-depleted cell fractions were superior to TG-enriched cell fractions in producing TCGF upon PHA stimulation. These supernatants induced intense proliferation of blast cell populations isolated from mixed leucocyte-tumour cell cultures (MLTC) established with PBL and irradiated allogeneic myelogenous leukaemic cells. Within 7 days of culture in TCGF, the number of MLTC blast cells increased approximately 300-fold. Concomitantly, the lytic activity (on a per-cell basis) of these populations against the corresponding myelogenous leukaemic cell targets increased approximately