Cell-mediated immunity in the neonatal calf

Abstract

To understand the immunological capabilities of the bovine neonate, the complete ontogeny of the bovine immune system must be understood. As in most species, the developing bovine fetus is deficient in a number of different cellular and humoral factors that play important roles in host defenses during postnatal life. In the bovine fetus, as in other species, the immune response appears to develop and mature sequentially. During this development, maternal cells and humoral factors serve as the major protective barriers to infectious agents. However, the newborn calf is essentially agammaglobulinaemic because of the syndesmochorial placentation that does not permit the transfer of maternal immunoglobulins to the fetal circulation. The newborn calf is dependent on the absorption of immunoglobulins from colostrum to provide adequate humoral immunity. Colostrum also contains numerous leukocytes. The role and relative importance of these cells are not clear. However, recent data suggest that these maternally derived cells may influence the development of effective cellular immunity.