INTERLEUKIN-4 RESPONSES IN ACUTE-LEUKEMIA PATIENTS WITH SEVERE CHEMOTHERAPY-INDUCED LEUKOPENIA

T lymphocyte functions in acute leukaemia patients with severe chemoth erapy-induced leucopenia were investigated using 3 different approache s: (i) analysis of serum concentrations of the T cell cytokine interle ukin 4 (IL4) demonstrated that serum ILA levels increased during compl icating bacterial infections. However, this response was modulated by a concomitant increase in serum levels of the potential IL4 antagonist soluble ILA receptor alpha chain (sIL4R alpha). (ii) Even during leuc openia a subset of T lymphocytes derived from leucopenic patients expr essed the activation markers CD25 (IL2 receptor), CD71 (transferrin re ceptor) and HLA-DR. (iii) Subsets of circulating CD4(+) and CD8(+) T l ymphocytes could undergo clonogenic proliferation in vitro, and a majo rity of these clones secreted IL4. CD4(+) clones showed higher IL4 lev els than CD8(+) clones. Our results indicate that T lymphocytes can be activated and contribute to cytokine responses in acute leukaemia pat ients with severe chemotherapy-induced cytopenia.