Immune cell kinetics in the ovine abomasal mucosa following hyperimmunization and challenge withHaemonchus contortus

Abstract

Sheep were sensitized by repeated infection with Haemonchus contortus L3, followed by a 12 week rest period, and an abomasal cannula was surgically implanted in all sheep. Seven of the sensitized sheep were subsequently challenged with 50 000 H. contortus L3 while 4 control sheep were challenged with saline. Biopsy samples were taken using a fibreoptic endoscope on days 0, 1, 2, 3, 5, 7 and 28 after challenge and leukocyte subpopulations quantified by (immuno)histology. Differential blood cell counts were performed on the same days. At the end of the trial, sheep showed significantly reduced worm burdens compared to unsensitized control sheep, confirming their resistance status. Both blood and tissue eosinophils, as well as tissue γδ TCR+ cells were rapidly elevated by day 1 post L3 challenge (pc), peaking at day 3 pc. There was a slight increase in tissue CD4 T cells at day 2 pc, peaking at day 3 pc while no significant changes in CD8 T cells were observed. B cells (CD45R+) increased later into challenged tissues with a peak at 5 days pc. All tissue lymphocyte subpopulations as well as tissue and blood eosinophils were reduced by day 7 pc before increasing again at day 28 pc, suggesting separate responses to larval and adult antigens. In contrast, globule leukocytes and mucosal mast cells only showed one peak at day 5 pc and 28 pc, respectively. Unexpectedly, globule leukocytes correlated significantly with tissue eosinophils but not mucosal mast cells. The results are consistent with an early eosinophil-mediated killing of L3, possibly recruited by IL-5 produced by γδ T cells. In contrast to post-mortem studies, abomasal cannulation allowed sequential analysis of both early and late time points in the same animal, providing a more complete picture of cellular interactions at both peripheral and local sites, and their correlation with the different stages of parasite development.

Fecundity in adult Haemonchus contortus parasites is correlated with abomasal tissue eosinophils and γδ T cells in resistant Canaria Hair Breed sheep

“…A significant positive correlation between ␥␦ T cells and eosinophil numbers at the abomasal mucosa has been reported in early infection and associated with resistance against the larval stages (Robinson et al, 2010). In this response, ␥␦ T cells were postulated to recruit tissue eosinophils through local IL-5 cytokine production, followed by antibody-mediated eosinophil killing of tissue larvae.…”

Effect of Experimental Infection withHaemonchus contortuson Parasitological and Local Cellular Responses in Resistant and Susceptible Young Creole Goats

“…Previous studies in immunized sheep showed that globule leukocytes were implicated in the immune exclusion of challenge larvae [27–29]. Recently, Robinson et al (2010) monitored the local cellular immune response in immunized sheep challenged with H. contortus and observed a peak of globule leukocyte infiltration in the abomasal mucosa at five days after infection [30]. In accordance with this study, our data suggest that globule leukocytes would be implicated in the response against larval stage of H. contortus a mechanism associated with the genetic resistance.…”

Immune and other factors modulating host resistance against gastrointestinal nematode parasites in sheep

“…This has been proved for T. circumcincta (Li et al, 2012;Shaw et al, 2012). While the association between serum IgA and infection ΑΡΣΕΝΟΠΟΥΛΟΣ Κ., ΣΥΜΕΩΝΙΔΟΥ Η., ΠΑΠΑΔΟΠΟΥΛΟΣ Η. mice and Robinson et al (2010) against H. contortus in sheep. Researchers have observed a rapid eosinophil recruitment around L4 larvae resulting to a considerable damage to H. contortus larval surface, especially in gastric pits of immunized sheep (Balic et al, 2006).…”