Detection of human factor B biosynthesis in culture supernatants and cell lysates by ELISA

We report here on the development of a simple, sensitive, convenient, and quantitative enzyme-linked immunosorbent assay for human factor B, a protein of the alternative complement pathway, by the sandwich method using goat anti-human factor B antibody. The assay described herein is reproducible and highly specific for human factor B. The assay was used to determine biosynthesis (cell lysates or extracts) and secretion (supernatants) of human factor B using human monocyte cell line U937. Phorbol myristate acetate strongly enhanced (10- to 20-fold) biosynthesis of factor B by U937. The combination of a sensitive enzyme-linked immunosorbent assay and phorbol myristate acetate enabled us to use a microculture system.