Further evidence for the B-cell nature of hairy cells. A study using immunostaining of splenic tissue with a wide panel of monoclonal antibodies.

Phenotypic characterization of neoplastic cells from 5 patients with hairy cell leukemia (HCL) was performed with 29 monoclonal and 6 polyclonal (anti-Ig) antibodies using immunoperoxidase staining of fresh frozen splenic tissue. Monotypic Ig was expressed in 4 cases, one case was non-expressive. Strong staining was obtained in all cases by monoclonal antibodies (MAs) specific for 3 pan-B-lymphocyte antigens (by anti-B 1, To 15, anti-Leu 12). Five other B-cell related antigens detectable with appropriate MAs (BA-1, anti-B2, DAKO-C3 b R, Tü 1, 38.13) were absent in all cases. The stainings with 13 T-cell associated MAs (OKT 3, OKT 4, anti-Leu 3 a, OKT 6, OKT 8, Tü 68, OKT 10, anti-Lyt 2, Tü 71, OKT 11, anti-Lyt 3, Tü 14, Tü 33) were all negative. Stainings with 4 MAs recognizing myelocytic and/or monocytic antigens (OKM 1, anti-Mo 1, anti-Mo 2, 3 C4) were also negative. We included 14 frozen biopsies with B-type chronic lymphatic leukemia (B-CLL) into our immunohistological study in order to establish phenotypic differences between HCL and B-CLL. Five MAs (Tü 1, anti-Lyt 2, Tü 71, BA-1 and anti-B2) gave consistently negative staining in HCL cases but positive staining in most or all B-CLL cases. The study provides significant evidence for the B-cell nature of HCL and also establishes important phenotypic differences between HCL and B-CLL.