Accumulation of guanylate binding proteins in patients treated with interferons

We have previously described an interferon (IFN)-induced protein with a molecular weight of 67,000. This protein has an affinity to guanylates and is thus called guanylate binding protein (GBP). The synthesis of GBP is inducible by IFNs in all human diploid fibroblast cell lines that we studied. To determine whether or not the GBP synthesis is IFN-inducible in humans as well as in cultured cells, we have studied the levels of GBP in the peripheral blood leukocytes (PBL) of patients treated with either type I or type II IFN. An increased GBP level was found the day immediately after treatment with either type of IFN, and the elevated GBP levels were maintained for at least 8 days. Among the patients studied, we found a higher level GBP accumulation (2.3x) in patients treated with IFN-beta than in those treated with IFN-gamma (1.6x). The increase of GBP in patients receiving IFN-gamma correlated with increases in class II histocompatibility antigens, HLA-DR and HLA-DQ in monocytes. Thus, the levels of GBP in peripheral blood leukocytes may be used as a parameter for the study of IFN responses in patients.