The effect of isoprinosine and levamisole on factors relevant to protection of calves against respiratory disease

Experiments to characterize the effects of two immunomodulators, namely, isoprinosine and levamisole, on factors relevant to the resistance of calves to respiratory infection were undertaken. Daily oral doses of isoprinosine decreased the influx of neutrophils into the respiratory tract, increased membrane immunoglobulin and complement receptor expression on cells from bronchoalveolar lavage samples and decreased the severity of respiratory disease. Additional intravenous doses produced similar effects on neutrophil migration to the respiratory tract and on membrane receptor expression, but the changes were no greater than those seen with oral isoprinosine alone. No significant changes in the anti-bacterial activity of cells in bronchoalveolar lavage samples followed isoprinosine treatment. In vitro incubation of pulmonary alveolar macrophages harvested from normal calves with isoprinosine increased their expression of immunoglobulin and complement receptors. Levamisole did not affect neutrophil migration to the lower respiratory tract or membrane receptor expression by pulmonary alveolar macrophages after in vivo or in vitro treatment. The immunomodulatory effects of isoprinosine beneficially increase the resistance of calves to respiratory disease, and are potentially useful in the control of infectious diseases of farm animals.