Antibacterial host defense: in vitro interaction of bacteria, serum factors, and leukocytes from precolostral dairy calves and their dams.

The bactericidal capacity of serum and peripheral blood leukocytes from newborn dairy calves (before receiving colostrum) and their dams for a strain of Escherichia coli and Staphylococcus aureus has been investigated. Comparative studies were conducted, using either unheated (freshly collected) and heated serums alone or in combination with cells from adult and newborn animals. Neither serum from newborn calves was able to kill either microorganism. Both microorganisms were sensitive to bactericidal activity of antibody and complement in unheated serum from adult cattle. On heating, serum from adult cattle lost bactericidal properties of the antibody-complement system. A cellular deficiency in phagocyte function in cells of newborn dairy calves was not evident, since they were as able to kill E coli and S aureus as cells from adult cattle, when incubated in the presence of the same opsonic source. Bactericidial activity was not evident when cells from newborn calves were incubated with heated autologous calf serum and S aureus or E coli. Unheated, autologous calf serum combined with cells from newborn calves exerted bactericidal capacity against S aureus but not E coli. The bactericidal capacity against S aureus of cells from newborn calves incubated with unheated serum from newborn calves did not differ from heated serum from adult cattle. However, there was a difference with E coli. The reasons for this phenomenon have not been determined, but may relate to natural, specific immunity of the neonate. Immunoglobulin and antibody concentrations in serums from calves and dams were determined. Most of the dams had bacterial agglutination titers to both microorganisms; the calves had either undetectable or low levels of antibody.