CD8A and Anal fistula: However, the ratios still decreased at these 2 time points for the complicated CD patients, indicating a more severe immunologic dysfunction caused by the complications.[34] Penetrating, structuring, and anal fistula signify that more CD8+CD28– T cells, the main force to suppress mucosal immunity, will be consumed, and more time will thus be required to increase the frequencies of CD8+CD28– T cells, which are derived from CD8+CD28+ T cells.[7,35]