Expression of the IL2 receptor alpha, beta and gamma chains in hairy cell leukemia.

The expression of the interleukin 2 (IL2) receptor chains was investigated by immunofluorescence and mRNA analysis in typical and variant hairy cell leukemia (HCL) cases. While typical hairy cells express both the alpha and the beta chains, variant HCL express the IL2 receptor beta chain on the surface membrane but not the alpha chain. Both typical and variant HCL have mRNA transcript of the p64 molecule (gamma chain). In B-cell chronic lymphocytic leukemia (B-CLL), EBV-transformed lymphoblastoid cell lines and normal B lymphocytes the expression of the IL2 receptor alpha and beta chains is very weak or negative. Furthermore, in B-CLL the IL2 receptor gamma chain shows a weaker expression compared to HCL. Both classic and variant HCL cases appear capable of proliferating in the presence of exogenous IL2, though the proliferative response of variant HCL appears lower than that of typical cases. Since in variant HCL the IL2 receptor alpha chain could not be induced by different stimuli, it appears that the CD25 antigen may not be essential in the process of IL2-promoted growth, while p75 and p64 play a primary role in IL2 activation. Taken together, it is suggested that the expression of IL2 receptors is up- or down-regulated during the process of B-cell lineage activation and differentiation.