In Vitro Immune Competence of Buffaloes (Bubalus bubalis) of Different Production Potential: Effect of Heat Stress and Cortisol

Twelve healthy lactating Murrah buffaloes of similar parity (3rd) between 90 and 120 days of lactation, selected from the herd of National Dairy Research Institute (Karnal, India) and maintained at managemental practices as followed at the Institute they were included in this experiment. The animals were divided into two groups based on their production level in previous lactation. The average milk production level of group 1 and II was 9.3 and 6 lit/day, respectively. Blood was collected from these buffaloes on three occasions 10 days apart. The lymphocytes were separated and cultured in RPMI 1640 medium with PHA-P for 24 h at 37°C in a humidified CO(2) incubator (95% air and 5% CO(2)). The lymphocyte responsiveness was also evaluated in response to the in vivo heat stress and in vitro cortisol. Mitogen-induced stimulation index was not affected by production level (P < .01). Stimulation index was significantly reduced (P < .01) in both the groups when cortisol was added at 2.0 ng level in the culture. However, in heat-stressed buffaloes stimulation index did not vary despite increasing levels of cortisol, thus indicating that lymphocyte may become cortisol resistant during periods of acute heat stress. The results showed that lymphocyte proliferation response can be effectively used to study buffalo cell-mediated immunity in vitro.