We studied the interaction of MB6A lymphoma and TAM2D2 T cell hybridoma cells with hepatocyte cultures as an in vitro model for in vivo liver invasion by these tumor cells. A monoclonal antibody against leukocyte function-associated antigen-1 (LFA-1) inhibited adhesion of the tumor cells to the surface of hepatocytes and consequently strongly reduced invasion. This effect was specific since control antibodies, directed against Thy.1 and against T200, of the same isotype, similar affinity, and comparable binding to these cells, did not inhibit adhesion. This suggests that LFA-1 is involved in the formation of liver metastases by lymphoma cells. TAM2D2 T cell hybridoma cells were agglutinated by anti-LFA-1, but not by control antibodies. Reduction of adhesion was not due to this agglutination since monovalent Fab fragments inhibited adhesion as well, inhibition was also seen under conditions where agglutination was minimal, and anti-LFA-1 similarly affected adhesion of MB6A lymphoma cells that were not agglutinated. The two cell types differed in LFA-1 surface density. TAM2D2 cells exhibited 400,000 surface LFA-1 molecules, 10 times more than MB6A cells. Nevertheless, the level of adhesion and the extent of inhibition by the anti-LFA-1 antibody were only slightly larger for the TAM2D2 cells.

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