ENZYMATIC EFFECT OF HYPODERMIN-A, A PARASITE PROTEASE, ON BOVINE LYMPHOCYTE MEMBRANE-ANTIGENS

The protease hypodermin A (HA) is produced by the parasitic warble-fly larva and is implicated in the modulation of the bovine immune system . This study examines the effect of this enzyme on the cell surface ma rkers of bovine lymphocytes. HA interfered with the binding of all ant i-lymphocyte receptor antibodies tested. Anti-BoCD2 and CD5 staining w as completely abolished But the mean fluorescence intensity (MFI) only was diminished for antibodies against BoCD4, CD8 and CD18. On the con trary, the MFI for anti-MHC Cl I molecules staining was increased. Thi s effect of HA began as early as one h, and was reversed by removal of HA. Heating or PMSF treatment, which both inhibit protease activity, abolished the action of HA on the surface antigens. The HA concentrati ons (100 mu g/ml) needed to alter antibody binding were similar to tho se that inhibited phytohaemagglutinin (PHA)-induced proliferation. The se results show that enzymatic activity of HA on lymphocyte surface ma rkers may be implicated in the inhibition of lymphocyte proliferation.