Experimental infections of calves have shown that M. bovis has both stimulating and suppressing effects on the bovine immune response such as stimulating the production of nitric oxide and TNF-α by macrophages, inducing apoptosis of lymphocytes, producing a lympho-inhibitory peptide, impairing lymphocyte responses to mitogens and suppressing the neutrophil oxidative burst [36-39]. The gene discussed is TNF; the disease is infection.