CD4 and tuberculosis: There is considerable evidence from various in vitro and in vivo studies that indicate the central role of T-cell subtypes (γδ, CD4 and CD8 T-cells) in host defense against mycobacterial pathogens, including M. bovis (POLLOCK et al., 1996; Cassidy et al., 2001), as demonstrated in the absence of T-cells, TB susceptibility increases (Mogues et al., 2001; Moguche et al., 2017).