CCR9 and enterovirus infectious disease: Apart from enterovirus infection, the variables with the highest importance in this analysis were the numbers of CD4+ T cells homing to the small intestine (CCR9+), particularly CD4+FOXP3+ (regulatory) T cells, and also circulating leukocytes, in particular neutrophils, and the fecal biomarker of enteropathy α1-antitrypsin.