THE IMMUNE-RESPONSE OF SHEEP SURGICALLY MODIFIED WITH INTESTINAL LOOPS TO CHALLENGE WITH TRICHOSTRONGYLUS-COLUBRIFORMIS

Aspects of the focal immune response to nematode challenge were invest igated in vivo in isolated loops of the upper small intestine of matur e sheep that were immunised by repeated infections with Trichostrongyl us colubriformis infective larvae (L3). Groups of 3 sheep were challen ged either through the loop (Group 1) or orally (Group 2) with T. colu briformis L3, the third group served as unchallenged controls (Group 3 ). Nematode specific antibody levels, mast cell proteinase levels (SMC P) and larval migration inhibition (LMI) activity were determined in l oop secretions for 4 weeks after challenge. The intestinal loops remai ned functional throughout the experiment, Groups 1 and 2 were re-chall enged 2 weeks after the first challenge, and all 3. Groups were slaugh tered 2 weeks later. Histopathological examination showed elevated num bers of globule leukocytes (GL) in both the nematode-challenged loop a nd unchallenged small intestine of Group 1 and small intestine of Grou p 2 indicating that nematode infections induce the local appearance of large numbers of GL. Oral, but not loop challenge caused increased an tibody levels in loop secretions when compared to unchallenged control s. Only loop-challenged sheep showed a peak in loop fluid SMCP levels 10-13 days after the first challenge which coincided with a peak in nu mbers of mucosal GL. The isolated loops of all 3 groups showed highly elevated numbers of eosinophils when compared to the intact small inte stine. Loop fluid of all 3 groups showed a high level of LMI activity reflecting the high level of nematode-resistance induced by the immuni sation procedures. Sheep in Groups 1 and 2 were both able to expel cha llenge infections, and when compared to Group 3, showed higher blastog enic activity of unstimulated cells derived from a mesenteric: lymph n ode in the region of the challenged part of the intestine. The present experiment showed that surgically constructed intestinal loops provid ed a model system by which the substantial changes associated with the local intestinal immune response to challenge with T, colubriformis c ould be investigated. Copyright (C) 1996 Australian Society for Parasi tology.