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 Trichostrongylus colubriformis and Ostertagia circumcincta infective (L3) larvae, drenched after the last infection and challenged with larvae of the same species, there was a significant increase in numbers of small intestine 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 LuGLs and TGLs in the small intestine but the ratio of these two cell types was lower in non-immunized than immunized sheep. In immunized sheep positive correlations were observed between LuGLs and levels of arylsulphatase and peroxidase in the intestinal mucus and between arylsulphatase 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 eosinophils correlated with nematode specific IgM levels in the intestinal mucus. In the abomasum, TGLs were present but not LuGLs. Sheep repeatedly 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 the isolated loop. Significantly more LuGLs were produced in sheep by allowing repeated T. colubriformis L3 infections to develop to adult stages compared to sheep treated with the same number of larvae, but where the infections were terminated by drenching at various intervals.