Cellular stress induces apoptosis. This stress should not be radioactive, chemical stress, inappropriate keeping conditions or viral infection. Cellular damage or cellular stress can only develop through lack of diet. The described manganese diets caused by tannin can suppress the normal function of anti-apoptotic proteins, paving the way for the activation of apoptosis

Perhaps the broilers that have been given tannin-rich foods suffer from more stress. This could mean that the effects of corticosterone on the immune system and the epithelial cells, as a component of it, acting negatively. This is confirmed by the fact that corticosterone can cause apoptosis even at a certain dose (Katharina Albrecht, 2007). Other pathways to apoptosis: activated CD8 + cell releases perforin (cytotoxic substance). This substance perforates the cell membrane and allows proteases to enter the cell and thus to induce apoptosis.

T-CD8 cells are able to produce IL2, IFN4, and to direct the inflammatory process in the direction of T helper lymphocytes, thus initiating activation of CD8 cells and destruction of the damaged cells (ROBERT and GRAHAM, 1995; HENNINO et al., 2000; GERD-RÜDIGER et al., 1998; KRUEGER et al., 2001). Activation of T-CD8 cells is also possible by antigen presentation: Normally, in the intestine, an antigen presentation (antigens in food) takes place through intestinal epithelial cells opposite to the T cells. this requires a co-simulation which can be done by cytokines. In the absence of co-stimulatory molecules and absence of cytokines that can replace this signal, there is tolerance (inactivated T cell) to the antigen.

NATHALIE et al., 1998 report that under certain circumstances, T-CD8 cells can be fully stimulated even without the second signal. The second signal can be replaced by cytokines. In the case of tannin, there appears to be a higher level of cytokines released by immune cells and epithelial cells, replacing the second signal in antigen presentation; then the T-CD8 cells can be activated

The large increase in goblet cells when feeding tannin-rich feed  emphasizes the role of activated T cells, since IL13, that of T cells is the key for differentiation of stem cells into goblet cells (ERIKE et al., 2006).