CD4 and colitis: Belotserkovsky et al. (2018) found that Shigella could target activated CD4 + T cells. Chen L. et al. (2018) found that specific diet could alter the intestinal microbiota of mice, leading to the proliferation of CD4 + T cells and promoting colitis caused by overexpression of IL23. Other studies have shown (Maslowski and Mackay, 2011; Chen B. et al., 2018; Linehan et al., 2018; Shenoy et al., 2019; Wu et al., 2019) that human-associated commensal bacteria have important regulatory effects on CD4 + T cells or CD8 + T cells.