Discrimination of a colony stimulating factor subclass by a specific receptor on a macrophage cell line

Utilizing the high affinity interactions between pure ¹²⁵I‐L cell colony stimulating factor and its receptor(s) on the murine macrophage cell line J774, a murine radioreceptor assay (RRA) has been developed. The murine RRA selectively detects a colony stimulating factor (CSF) subclass (CSF‐1) previously defined by murine radioimmunoassay (RIA) (E.R. Stanley, Proc. Nat. Acad. Sci., USA, 76:2969–2973 ('79)). CSF‐1 stimulates macrophage production exclusively, and the occurrence of the CSF‐1 receptor(s) appears to be restricted to cells of the mononuclear phagocytic system (L.J. Guilbert and E.R. Stanley, J. Cell Biol. 85:153–160 ('80)). The murine CSF‐1 RRA failed to detect a variety of other CSF subclasses, growth factors, and hormones. In contrast to data obtained with the murine CSF‐1 RIA, human CSF‐1 (e.g., human urinary CSF) is detected by the mouse CSF‐1 RRA almost as sensitively as murine CSF‐1. In addition, there was an absolute correlation between CSF‐1 levels determined by murine CSF‐1 RRA and those determined by a human CSF‐1 RIA for a variety of human CSF‐1 sources. The murine CSF‐1 RRA is a sensitive (sensitivity 5 units or 1.0 femtomole of CSF‐1 protein), rapid, and highly specific assay for CSF‐1 in both murine and human sources.