Isolation and characterization of head kidney derived macrophages of Labeo rohita

Macrophages play a significant role in non-specific defense mechanisms of all vertebrates against pathogens. One critical element in the area of fish immunology is the unavailability of in-vitro model of immune cells. Therefore, it is essential to develop methods for harvesting and culture of macrophages for assessing innate immune functions of rohu, Labeo rohita, an important culture fish of India. Head kidney leukocytes from were isolated by density gradient sedimentation, so as to exclude other cells. Among isolated leukocytes, only macrophages showed the unique property of sustained adherence on plastic surfaces. These cells exhibited optimum growth at 28 degrees C in L-15 containing 20% FBS. Cultured head kidney macrophages (HKM) demonstrated the property of phagocytosis as evidenced by engulfment of yeast cells. Bacterial lipopolysaccharide (20 mu g/ml) resulted in functional activation of macrophages as seen by enhanced reactive oxygen and nitrite production; and lysosomal enzyme activity. These results show that in-vitro model of HKM cells can be used to study the role of macrophages in innate immune responses against various immunomodulators.