Immunological and molecular biological identification of a true case of T-hairy cell leukaemia.

A hairy cell leukaemia (HCL) patient is presented in whom the peripheral blood mononuclear cells (PBMCs) carried suppressor T-cell markers (CD3+, CD2+, CD8+/CD4-, CD38+). Analysis of genomic DNA of PBMNC showed the presence of a monoclonal population of T cells, the T-cell receptor (TCR) beta-chain gene being rearranged on both alleles (DR/DR), while the immunoglobulin (Ig) heavy chain-genes were in germline configuration. The neoplastic cells were found to react with the monoclonal antibody RAB-1 - originally described as belonging to the B lineage-restricted monoclonal antibodies - and to carry RAB-1/CD-8 in a double marker assay. Natural killer activity of PBMNCs against K562 target cells was severely reduced, while the cells were found to exert strong antibody-dependent cellular cytotoxicity.