Similarly, CD8+ Trm cells (CCR7-CD45RA+/-CD69+) were decreased in all layers of the appendix combined in children with complex compared to simple appendicitis (epithelium simple appendicitis median 18%, IQR 12-21% versus complex appendicitis median 10%, IQR 3-27%; lamina propria median 34%, IQR 29-45% versus median 11%, IQR 9-32%; muscular layer median 25%, IQR 19-26% versus median 6%, IQR 4-11%) (Figures 3A, C). Here, CCR7 is linked to appendicitis.