Monoclonal antibodies to rat C apolipoproteins: production and characterization of a unique antibody whose binding to apoC-I is inhibited by nonionic detergents.

Four monoclonal antibodies to rat apo (apolipoproteins) C were produced. Three of the monoclonals reacted to apoC-I and one to apoC-III. The IgG monoclonals LRB 21 and LRB 45 recognized a spatially close together or identical apoC-I epitope. The monoclonal LRB 80, however, recognized an epitope that is close to, but distinct from, that recognized by LRB 45 and LRB 21. The antibody LRB 45 recognized an apoC-I epitope that is specific for rat apoC-I, and the antibody did not cross-react with dog or human lipoproteins. Rat apoC-I could be detected in all lipoprotein density fractions, but not in the d greater than 1.21 g/ml fraction. Freezing and thawing of serum did not alter the antibody antigen binding. However, lipolysis of whole serum resulted in a 30% increase in antigenic epitope expression. Antibody antigen reaction could be inhibited by subcritical micellar concentration of nonionic detergents. The inhibition was specific but could be partially reversed if lipid-containing serum was used as a dilution buffer. On feeding animals a diet of olive oil and cholesterol for 2 weeks, apoC-I levels decreased.