Evaluation of the role of Con-A and PHA-P induced leucocyte conditioned medium in activating bovine blood monocytes pulsed with Mycobacterium bovis BCG

Bovine tuberculosis, a disease of public health importance, caused by Mycobacterium bovis has been a cause of great sufferings and economic losses to human being and his livestock. The monocyte/macrophage is an important arm of the immune system, acts non-specifically to kill microorganisms, but mycobacteria multiply, persist and remain viable in resting monocytes. To kill this facultative intracellular pathogen, the activation of monocytes is necessary. The study was conducted to evaluate the role of Con-A and PHA-P induced leucocyte conditioned medium (LCM) in activating bovine peripheral blood monocytes while combating M. bovis BCG. Four healthy bovine calves, free from tuberculosis, 6–12 months of age, were inoculated intramuscularly with 0.5 mg of pure culture of M. bovis BCG per animal and tested positive for sensitization after 1 month by DTH skin testing, ELISA and LTT using PPD as an antigen. Blood monocytes from the M. bovis BCG sensitized animals were in vitro stimulated with Con-A (10 μg/ml)-LCM and PHA-P (5 μg/ml) - LCM (20% in RPMI-1640 GM) and tested for various parameters of activation. In vitro both Con-A and PHA-P induced leukocyte conditioned medium (LCM) enhanced several activities of the bovine blood monocytes viz., phagocytosis, immune phagocytosis, antibody dependent cellular cytotoxicity, nitrite production and the intracellular killing of M. bovis BCG at different time intervals of stimulation, which resulted in increased destruction of the mycobacteria.