GROWTH OF LUCILIA-CUPRINA LARVAE FOLLOWING TREATMENT OF SHEEP DIVERGENTLY SELECTED FOR FLEECE ROT AND FLY STRIKE WITH MONOCLONAL-ANTIBODIESTO T-LYMPHOCYTE SUBSETS AND INTERFERON-GAMMA

Colditz I. G., Eisemann C. H., Tellam R. L., McClure S. J., Mortimer S . I. & Husband A, J. 1996. Growth of Lucilia cuprina larvae following treatment of sheep divergently selected for fleece rot and fly strike with monoclonal antibodies to T lymphocyte subsets and interferon gamm a. International Journal for Parasitology 26: 775-782. Intensive lymph ocytic infiltration of the underlying dermis occurs during cutaneous m yiasis caused by larvae of the blow fly, Lucilia cuprina. To determine the effect of this infiltrate on larval growth, monoclonal antibodies (mAb) to CD4, CD8 or WC1 lymphocyte subset determinants were injected intravenously before and during experimental infection of sheep with larvae. The effect of intravenous injection of mAb to ovine interferon (IFN) gamma was also examined. The experiments were performed in 18-m onth-old maiden ewes with genetic resistance or susceptibility to the disease complex, bacterial dermatitis/cutaneous myiasis. mAbs induced profound depletion of CD8+ and WC1+ subpopulations from blood and skin at sites of larval growth. mAb to CD4+ gave only a moderate reduction in lymphocytes from blood or skin. mAb treatments did not modify larv al growth or survival at 20 or 50 h after infection. Larval growth rat es did not differ between resistant and susceptible genotypes. No evid ence was found for a role of T lymphocyte subpopulations or the cytoki ne IFN gamma in modifying larval growth during the first 50 h of infec tion. It seems unlikely that T lymphocyte-dependent immunological effe ctor mechanisms contribute to the lower prevalence of fly strike seen in the resistant genotype in the field. Copyright (C) 1996 Australian Society for Parasitology.