The high therapeutic efficiency of lymphotogic purine analogues, pentostatin and cladribine in hairy cell leukaemia which expres the antigen CD25 (alpha chain interleukin-2 receptor) suggests the hypothesis whether protracted cellular immunodeficiency after treatment does not represent an important mechanistu of control of this specific lymphoproliferation. The authors analyzed a group of 45 patients with CD25-positive hairy cell leukaemia treated with cladribine. In addition to the therapeutic response they evaluated also the state of cellular immunity during the subsequent months and years following cladribine administration. The regression lines of the development of different sub-populations CD4, CDS and CD56-positive cells, interleukin-2 and its soluble receptor esere evaluated separately in patients with persistent remission and patients with growth of the tumourous mass. Although this retrospective analysis provides only limited information we can deduce from it a long-term decline of CD4 lymphocytes correlating with the relatively low incidence of clinical progression of hairy cell leukaemias. The results of this clinical observation are consistent with some reported clinical and egperimental observations.

        Key words: Hairy cell leukaemia - 2-chlorodeogyadenosine - 1VK cells - T-lymphocytes - Interleukin-2 - Interleukin-2 receptor