Signal requirements for activation of leukaemic T cells from a chronic lymphocytic leukaemia (T-CLL)

Abstract

SUMMARY In order to define the signal requirements Tor leukaemic T cell activation, the proliferation and interleukin-2 (IL-2) production of peripheral lymphocytes from a patient with a HTLV-I., CD4+, CD45RA+ CD45RO+ CD25- T-CLL were evaluated after the delivery of different stimuli. Unlike resting CD4+ normal T lymphocytes that can be activated only by a two-signal stimulation. T-CLL cells proliferated and released IL-2 in response to a pair of anti-CD2 monoclonal antibodies (MoAbs) or concanavalin A (Con A) in the absence of both accessory cells (AC) and phorbol myristate acetate (PMA). The two stimuli were also able to induce CD25 expression within 12–20 h on the majority of T-CLL cells. A response to anti-CD3 and anti-CD28 MoAbs was detected only in the presence of PMA, similar to that observed in normal resting T lymphocytes matched for phenotype. Both Con A-and CD2-induccd proliferation were strongly inhibited by the addition of anti-CD2S MoAb. Furthermore, T-CLL lymphocytes acquired anti-tumour lytic activity after culture in the presence of PMA and ionomycin. We conclude that HTLV1 CD25 T-CLL can be characterized not only by morphological and phenotypical studies but also on the basis of signal requirements for cell activation.