DETECTION OF HOMOCYTOTROPIC ANTIBODY IN LAMBS INFESTED WITH THE LOUSE, BOVICOLA-OVIS, USING A BASOPHIL HISTAMINE-RELEASE ASSAY

The utility of a basophil histamine-release assay using washed whole b lood cells was examined in lambs and was used to determine if homocyto tropic antibody with specificity for Bovicola ovis was produced in res ponse to infestation with the louse. Maximal histamine release in the assay in response to Concanavalin A, anti-ovine IgE monoclonal antibod y and, in sensitized lambs, to B. ovis antigen ranged from 18 to 48%. Histamine release from blood cells in response to B. ovis antigen was significantly higher in louse-infested lambs than in louse-naive lambs and was significantly correlated with louse and cockle scores. Passiv e cutaneous anaphylaxis (PCA) tests were negative with sera obtained f rom the lambs at the same time as blood for the basophil histamine-rel ease assay. Serum histamine levels also were significantly higher in t he louse-infested lambs than in louse-naive lambs and were significant ly correlated with louse and cockle scores. The present results suppor t a role for B. ovis-specific homocytotropic antibody in the developme nt of cockle and indicate that the basophil histamine-release assay is more sensitive than the PCA test. (C) 1997 Elsevier Science B.V.