SUMMARY
Mastitis is a complex disease responsible for huge economic losses to the dairy sector. The causal organisms include a wide variety of micro-organisms including several species of bacteria. Escherichia coli has been identified as one of the most common gram-negative bacteria causing clinical mastitis in cattle. The immune system, of different species and/or breeds, tries to combat these pathogens in an inconsistent manner with differential mode and intensity of immune response, eventually producing contradicting outcomes of this disease. Several reports suggest the existence of variability among different animal breeds/species, resulting in a dissimilar outcome of this disease among them. In order to evaluate the variation among different breeds/species, the present study was undertaken to examine the stimulant effect of E. coli lipopolysaccharide (LPS) on peripheral blood mononuclear cells (PBMCs). The PBMCs were harvested from blood samples of crossbred cattle, Tharparkar cattle and Murrah buffaloes. After 6 h of in vitro stimulation, qRT-PCR was employed to measure the relative mRNA expression levels of CCL5, IL-1ß, IL-12ß, IFN-? and IL-10 genes in stimulated and unstimulated PBMCs. The selected genes revealed significant differences in the pattern of innate immune response among crossbred cattle, Tharparkar cattle and Murrah buffaloes. The results clearly indicate the presence of variation in the outcome of immune response even when the immunocytes were stimulated with the same dose of the antigen.