Development of a micro enzyme-linked immunosorbent assay for antibodies against liver-specific membrane lipoprotein

Guinea pig antisera raised against human and rabbit liver-specific membrane lipoprotein (LSP) have been used to develop a rapid, reproducible and sensitive solid-phase, enzyme-linked immunosorbent assay (ELISA). The ELISA was used in a series of cross-inhibition experiments to define and quantitate the antigenic specificities of these antisera. The results confirm previous findings that LSP contains both liver-specific and liver non-specific antigens. In addition, it is shown that both human and rabbit LSP contain liver-specific antigens that are species-specific, as well as others that are species cross-reactive. Binding to human LSP was detected by the ELISA with 11 of 13 anti-LSP-positive (by radioimmunoassay) sera from patients with HBsAg-negative chronic active hepatitis. Similar binding was also found with 10 of 11 sera from patients with systemic lupus erythematosus and with 7 of 14 with rheumatoid arthritis --all of which were negative for anti-LSP by radioimmunoassay. It is suggested that immune complexes in these sera might bind to IgG-Fc receptors in LSP and that caution should be exercised in the interpretation of data from ELISA-based studies of anti-LSP in human sera.