In-vitro immunomodulation of fish macrophages by macrophage activating factors derived from head kidney leukocytes of Labeo rohita

Head kidney leucocytes of rohu, Labeo rohita, were costimulated with two mitogens i.e. Concanavalin A (Con A) and Phorbol myristate acetate (PMA) to trigger the release of macrophage activation factor (MAF). Effect of different concentrations of MAF on important functional properties of rohu head kidney macrophages (HKM) was studied individually and also in combination with varying concentrations of bacterial lipopolysaccharide (LPS), a known immunomodulator of macrophages. Our results revealed that co-stimulation of rohu macrophages with varying dilution of MAF (1: 2 to 1: 64) and different concentrations of LPS (5 mu g-40 mu g/ml) inhibited reactive oxygen species (ROS) production. Maximum production of ROS was observed with 1: 8 dilution of MAF alone. Synergistic effect of MAF and LPS combination (1: 4 dilution of MAF and 10 mu g ml(-1) LPS) was seen on nitric oxide production by HKM of rohu. Similarly, lysozyme activity was also enhanced after co-stimulation with the MAF and LPS as compared to MAF or LPS alone. These data suggest that leucocytes of rohu could be stimulated to produce MAF which can be used for functional activation of HKM.