CD4 and colitis: In an experimental study from 2015, Maxwell J et al. showed, in a mouse model with colitis, that IL-17A/RA inhibition led to a number of negative consequences: an elevated intestinal barrier permeability, with marked fragility of the intestinal mucosa, an imbalance between effector and regulator CD4+ T lymphocytes, as well as a decreased expression of antimicrobial peptides [54].