Reduced production of tumor necrosis factor by mononuclear cells in hairy cell leukemia patients and improvement following interferon therapy

In 16 patients with hairy cell leukemia (HCL) there was a marked reduction in the production of cytotoxins (CTXs) by peripheral blood mononuclear leukocytes in response to stimulation in vitro by phytohemagglutinin (PHA), 4β‐phorbol‐12‐myristate‐13‐acetate (PMA), or Sendai virus. CTX yields of 23.5 ± 21.5 U/ml, 15 ± 18 U/ml, and 12.1 ± 12.1 U/ml were obtained in response to PHA, PMA, and Sendai virus, respectively, as compared with corresponding yields of 207.3 ± 93.1, 154 ± 37.4, and 205.2 ± 62.4 in healthy controls. The extent of reduced production of CTXs appeared to be correlated with the severity of the disease. Systemic interferon (IFN) administered to four patients caused CTX production to improve in response to PHA (147.5 ± 55.1 U/ml compared with pretreatment values of 14.1 ± 6 U/ml, P < 0.05). However, CTX production in response to Sendai virus remained low. The extent to which CTX production by hairy cell leukemia mononuclear cells was reduced was proportionate to the observed decrease in monocyte counts. However, the degree to which CTX production improved after IFN treatment was significantly greater than the observed increase in monocyte counts. The major CTX induced by PHA in mononuclear cells of healthy donors and of IFN‐treated HCL patients was identified as tumor necrosis factor‐α.