CD44 is involved in porcine natural cytotoxicity.

A polyclonal anti-porcine CD44 antibody was used to elucidate the possible role of the CD44 molecule in porcine natural cytotoxicity. It was found that the antibody inhibited porcine NK activity in a dose-dependent manner. The inhibition was reversed by incubation with soluble porcine CD44. The F(ab')2 but not Fab fragment of the antibody was effective, suggesting that the CD16 pathway was not involved and that cross-linking of the CD44 molecule might be essential for the inhibition. The antibody exerted the inhibition by acting on the effector cells, without preventing them from forming conjugates with the target cells. Kinetic studies showed that the inhibition was exerted at a late postbinding stage.