Cytokine mRNA expression in cattle infected with different dosages of Mycobacterium bovis.

Cytokine mRNA expression of pro-inflammatory cytokines, i.e., interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha) and anti-inflammatory cytokines, i.e., interleukin-4 (IL-4), interleukin-10 (IL-10) was quantified using quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) in cattle infected with different doses (1-1000 colony-forming units (cfu)) of Mycobacterium bovis. RNA was extracted from the Hepes glutamic acid buffer mediated organic solvent protection effect (HOPE) fixed lymph node tissues using Trizol method. The expression levels of all the four cytokines gradually increased in cattle infected with 1 cfu-1000 cfu. Statistical significance (P<0.05) was observed for the cytokines IFN-gamma, IL-4 and IL-10 between the cattle infected with 1 cfu and 1000 cfu. Though there was an increase in the expression levels of TNF-alpha from cattle infected with 1 cfu-1000 cfu, this difference in expression was not statistically significant (P>0.05). The increase in the levels of IFN-gamma indicates that the host may be responding to control the infection and the increased level of IL-4 and IL-10 which are anti-inflammatory cytokines, suggests that these cytokines are trying to protect the host by reducing the inflammation and also by controlling the levels of TNF-alpha (the cytokine that may cause tissue damage).