IMMUNIZATION OF SHEEP AGAINST PARASITIC NEMATODES LEADS TO ELEVATED LEVELS OF GLOBULE LEUKOCYTES IN THE SMALL-INTESTINE LUMEN

In sheep that had been given three immunizing infections with Trichost rongylus colubriformis and Ostertagia circumcincta infective (L3) larv ae, drenched after the last infection and challenged with larvae of th e same species, there was a significant increase in numbers of smalt i ntestine mucosal tissue globule leukocytes (TGLs) and lumenal globule leukocytes (LuGLs) compared with sheep that had only been drenched and challenged. There was a positive correlation between the numbers of L uGLs and TGLs in the small intestine but the ratio of these two cell t ypes was lower in non-immunized than immunized sheep. In immunized she ep positive correlations were observed between LuGLs and levels of ary lsulphatase and peroxidase in the intestinal mucus and between arylsul phatase and larval migration inhibition (LMI) activity in mucus. Lumen eosinophils correlated with blood eosinophils, serum antibody against T. colubriformis correlated with peroxidase in the mucus and blood eo sinophils correlated with nematode specific IgM levels in the intestin al mucus. In the abomasum, TGLs were present but not LuGLs. Sheep repe atedly infected with T. axei also had significantly more LuGLs in the small intestine than control animals. Two sheep that had a surgically prepared isolated small intestinal loop, after oral infection with T. colubriformis had TGLs and LuGLs in the intact intestine, but not in t he isolated loop. Significantly more LuGLs were produced in sheep by a llowing repeated T. colubriformis L3 infections to develop to adult st ages compared to sheep treated with the same number of larvae, but whe re the infections were terminated by drenching at various intervals.