Proliferative response of lymphocyte subpopulations differing in avidity for sheep red blood cells after stimulation with normal allogeneic and tumour cells.

Lymphocytes from normal donors were cultured with cell lines of erythroid (K562) and lymphoid (Bri8) origin, fresh cells derived from chronic myeloid leukaemia patients (FLC), T-depleted normal peripheral blood lymphocytes (PBL) and normal bone marrow cells (NBMC). The proliferative response to these stimulator cells was evaluated in both the total lymphocyte population and in subpopulations with different affinity receptors for sheep red blood cells (SRBC), on the second, fourth and sixth days of culture. No DNA synthesis was induced by the K562 cell line, while Bri8 cells induced a proliferative response greater than that observed against PBL. No differences in the DNA synthesis pattern were observed when NBMC and FLC were used as stimulators which was comparable with that for PBL. There was a correlation between the degree of activation of the culture and the changes in size of the responding SRBC binding cell population (ET+). A progressive increase with duration of the cultures in the number of SRBC high avidity cells (EH+) and a parallel contraction of the SRBC low avidity (EL+) and E- cell populations was generally observed, so that EH+ and ET+ fractions gave similar values at the later time points. The analysis of [3H]-thymidine uptake of E+ and E- fractions on days 3 and 6, in FLC and NBMC-stimulated lymphocytes showed a prevalent involvement of E- cells on day 3, while on day 6 the majority of dividing cells belonged to the E+ compartment. A higher recruitment of E- cells in the early phase of the response was observed in FLC-stimulated lymphocytes. The participation of non-T cell populations in the proliferative response against allogeneic normal and tumour antigens is discussed.