Characterization of the antibodies in normal rabbit serum responsible for the lysis of NK-sensitive target cells

Abstract

Normal rabbit serum has previously been reported to lyse a spectrum of murine lymphoid cell lines characterized by being susceptible to natural killer (NK) cells. Although we have failed to confirm that a simple correlation exists between the susceptibility of target cells to NK cells and to normal rabbit serum, we were able to characterize a number of naturally occurring anti-carbohydrate antibodies which selectively lyse NK-susceptible lymphoma cells. The antibodies present in normal rabbit serum responsible for lysing an NK susceptible clone derived from the DBA/2 lymphoma L5178Y (27v−IC2) were found to be directed against the terminal β- N-acetylgalactosamine sugar present on the neutral glycolipid gangliotriosylceramide. Interestingly, normal rabbit serum did not lyse an NK-insusceptible variant, derived from the same lymphoma, which lacked gangliotriosylceramide. YAC-1 target cells, the prototype target for murine NK cells, were insusceptible to normal rabbit serum. However, following neuraminidase treatment, such cells were lysed by an antibody in normal serum directed against terminal β-galactose residues. The anti-β-galactose reactivity was directed against the carbohydrate structure of gangliotetraosylceramide. These findings are discussed in light of the hypothesis that NK cells interact with susceptible target cells through cell surface glycoconjugates.