Immunohistochemical studies of the spleen in hairy-cell leukemia.

Immunohistochemical studies of 10 spleens from patients with hairy-cell leukemia (HCL) with a battery of monoclonal and heterologous antibodies were performed in order to obtain information on the phenotype of the neoplastic cells and the admixture of reactive cells. The hairy cells (HCs) were shown to react with several anti-B-cell antibodies (Y29/55, Leu10, HLA-DR), but only a minority of cases showed reactivity with antibody BA-1. The cells of all cases were nonreactive with anti-T and/or anti-macrophage antibodies. In contrast with cell-suspension studies, in immunohistochemical studies the HCs did not react with antibody OKM1. The reactive T-lymphocytes showed a shift toward T helper cells in the red pulp, but not in the white pulp. It was confirmed that "pseudosinuses" and "bloodlakes" are outlined by HCs and not by sinus-lining cells: the lining cells of the blood lakes were Y29/55+ and Leu10+, but negative with antibodies known to react with sinus-lining cells (Leu2a, BA-2). These data suggest that immunohistologic studies of the spleen in patients with HCL can be helpful in differential diagnosis and can provide information concerning the reaction of splenic tissue to the infiltration by hairy cells.