Murine monoclonal antibodies against "liver specific lipoprotein" (LSP) defining three antigenic sites which differ in tissue- and species-distribution and subcellular location.

The tissue and species cross-reactivity of three monoclonal antibodies against human liver-specific lipoprotein (LSP), as well as the subcellular locations of the respective target antigens, has been investigated using an enzyme-linked immunosorbent assay (ELISA). Antibody D6 was widely tissue cross-reactive and bound to human and rabbit but not rat, mouse or guinea pig tissues. This antibody bound to a particulate antigen localized in the microsomal fraction of rabbit liver, and distinct from enzyme markers for plasma membrane (5'-nucleotidase) and endoplasmic reticulum (glucose-6-phosphatase) in its sedimentation properties on sucrose density gradients. Antibody A9/63 bound to human liver and pancreas, but not kidney, spleen, adipose tissue, skeletal muscle, small intestine or heart, and also bound only to human and rabbit tissues. This antibody bound to a particulate antigen in pancreas, but a soluble antigen in liver. Antibody B20 bound to all tissues from all species tested, with the exception of guinea pig, and bound to particulate antigens in adipose tissue and pancreas but soluble antigens in other tissues (including liver). In addition to emphasizing the immunochemical complexity of LSP, these experiments demonstrate the suitability of monoclonal antibodies for analysis of its constituent antigens.