Expression of Ia-antigens on guinea pig Kupffer cells. Studies with monoclonal antibodies.

The expression of the Ia-antigen on guinea pig Kupffer cells was studied employing two monoclonal antibodies against two different determinants of the Ia-molecule. The study was performed in situ on liver sections and on isolated highly purified Kupffer cells kept in culture up to 6 days. The influence of guinea pig hepatocyte culture supernatant and of supernatants of phytohemoagglutinin (PHA)-stimulated human peripheral blood lymphocytes (PBL) on the Ia expression was measured. Immunofluorescence staining of cryostat sections revealed that the monoclonal antibodies used are able to detect Ia-antigens on liver macrophages in situ. The in vitro studies strongly suggest that all Kupffer cells are able to express Ia-antigens. The expression of Ia-antigens on Kupffer cells decreased during the culture time and was no longer detectable on day 5. At this time, incubation of the cell cultures with PBL conditioned medium induced the reexpression of Ia-antigens. Supernatants from guinea-pig hepatocyte cultures did not have any negative influence on the expression of the Ia-antigen on Kupffer cells in vitro. These data support the hypothesis that liver macrophages have the potential to behave immunologically as accessory cells and might contribute to local immune responses in acute as well as chronic states of liver diseases.