[Production and secretion of BSF2/IL6 in a case of hairy cell leukemia with polyclonal hypergammaglobulinemia]

A 55-year-old woman was first seen in October 1986, because of splenomegaly, moderate anemia and leukocytosis. The hemoglobin was 8.8 g/dl, platelet count 24.4 X 10(4)/microliters, and the white cell count 23,800/microliters with 73% atypical lymphoid cells. The bone marrow nucleated cell count was 99,000/microliters with 36% lymphoid cells. These atypical lymphoid cells showed hairy appearance under phase-contrast microscopy, and were positive for tartrate-resistant acid phosphatase. These cells showed the surface phenotype of CD10, CD19, CD20, Leu M5, HCM, and IgG K. Biochemical data revealed marked polyclonal hypergammagloburinemia (PHG) of IgG type (IgG 8756 mg/dl). To elucidate the mechanism of the PHG, we investigated whether hairy cells produce interleukin 6 (IL-6) and express IL-6 receptor. The culture supernatant of these hairy cells increased 3H-thymidine uptake of a IL-6 dependent hybridoma clone (MH60) in a dose-dependent manner. These cells were stained with anti-IL-6 antibody using immuno-cytochemical technique. Our results suggested that these hairy cells produce and secrete IL-6. Immunocytochemical staining with anti IL-6 receptor antibody and the binding assay with 125I-labelled recombinant IL-6 revealed that these cells express little or no receptors for IL-6. It was therefore suggested that IL-6 produced by hairy cells in this case is not an autocrine growth factor for these cells but may play a role in development of PHG by stimulating normal B lymphocytes to produce an excessive amount of immunoglobulin.