A cellular analysis of immunosuppression in cattle with mucosal disease

Abstract

Eleven cattle with mucosal disease ( MD) were investigated to determine the constitution and function of the cells participating in the immune response. The total numbers of blood mononuclear cells varied within the normal range but a poor response of the lymphocytes to mitogen stimulation indicated a state of immunosuppression in the cattle with MD. Identification of subpopulations of the mononuclear cells revealed that eight of the cattle with MD had an increased proportion of B cells. However, the proportions of monocytes and T cells were in the normal ranges, resulting in a low proportion of cells not identified as being either B or T cells (null cells). Three of the cattle with MD had an increased proportion of cells with receptor for the Fc part of IgG (Fc γ+ cells). Bovine Fc γ + cells have previously been shown to exert suppressor activity, as was also demonstrated in the present study by increased mitogen induced lymphocyte stimulation following removal of the Fc γ+ cells. The effect of depletion of Fc γ+ cells was at least five-fold greater in the two cattle with MD tested than the two controls. It appears that a diminished number of null cells and, or, increased suppressor cell activity might contribute to the observed immunosuppression in cattle affected with md.