T and B cell activation profiles from cows with and without Johne's disease in response to in vitro stimulation with Mycobacterium avium subspecies paratuberculosis

Johne's disease (JD) is a chronic wasting disease of ruminants caused by infection with Mycobacterium avium subspecies paratuberculosis (MAP). JD is particularly problematic on US dairy farms: estimates show that over 50% of farms are MAP-contaminated and as many as 91% of dairy herds could be infected. Although estimates vary widely, JD may cost the dairy industry between $200 million and $1.5 billion every year. One major obstacle to JD management is that JD is difficult to detect in many animals, in part due to the variable immunity against MAP demonstrated by JD+ cattle. To characterize the diversity of immune responses against MAP, peripheral blood mononuclear cells from 154 JD test negative and 96 JD test positive cows from the same dairy herds were stimulated with MAP in vitro. The activation of CD4+, CD8+ and γδ T cells and surface IgM+ B cells was measured using flow cytometry. CD4+CD45R0+ T cells, γδ+MHCII+ and γδ+MHCII- T cells and SIgM+ B cells from JD test positive cows all exhibited increased proportions expressing CD25 after MAP stimulation, while CD8+ T cells did not demonstrate increased CD25 expression in response to MAP.