Interferon-gamma (IFN-gamma) is a cytokine known to exert an important immunological role on astrocytes and oligodendrocytes. As a receptor for IFN-gamma has been demonstrated on murine astrocytes, we have searched for a specific receptor on the cell surface of pure mouse oligodendrocytes maintained in tissue culture. Using recombinant murine IFN-gamma labelled with 125I, we have established the basic physicochemical parameters of the binding. A single receptor was found with a Kd of 1 x 10(-9) M. The number of receptors per cell was 3000-4000 and its molecular weight, as determined by cross-linking experiments, is 87,000. The binding of IFN-gamma to its oligodendrocyte receptor is saturable, specific and temperature-dependent. The receptor-IFN-gamma complex is quickly endocytosed at 37 degrees (the half-time of maximal internalization is around 1 min). Some cytokines, such as interleukin-1 alpha and interleukin-6, up-regulated the expression of the oligodendrocyte receptor, but others, such as tumour necrosis factor-alpha, did not. A dramatic increase in receptor expression is induced by lipopolysaccharide but it is not detectable after treatment with concanavalin A.