Detection of membrane and soluble interleukin‐6 receptor in lymphoid malignancies

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Abstract
Summary. We studied the membrane expression of the gp80 chain of IL‐6 receptor (IL‐6R) by quantitative flow cytometry in chronic lymphocytic leukaemia (CLL) and leukaemic centrocytic lymphoma using a panel of seven monoclonal antibodies. IL‐6R was detected in 18/26 CLL cases and 4/7 lymphoma cases, with a mean antigen density <3000 molecules/cell. Multiple labelling experiments confirmed the IL‐6R expression by neoplastic cells. Specific mRNA was found by RT‐PCR in neoplastic cells. A specific ELISA test was designed using two anti‐IL‐6 receptor MAbs to measure the serum soluble IL‐6R (sIL‐6R) in CLL (n = 48), B‐cell non‐Hodgkin's lymphoma (NHL; n = 40), and monoclonal gammopathy (MG; n = 32). SIL‐6R was higher in CLL (170±12.6ng/ml) in NHL (160 ± 12ng/ml) and MG patients (183±23ng/ml) than in age‐matched controls (100 ±5.6 ng/ml; P < 0.001) and higher in high‐grade than low‐grade NHL. No correlation was noted with a previous treatment. Among CLL cases the patients classified as stage B according to the Binet's staging of the disease had the highest sIL‐6R values, thus suggesting a link with tumour cell mass.