Accumulation of CRTAM⁺ CD4⁺ T cells in the inflammatory and mucosal tissues. (A) CRTAM⁺ CD4⁺ T cells in the lung of influenza virus–infected mice. CD4⁺ T cells were prepared from the lung of influenza virus–infected mice, and simulated with anti-CD3/CD28 Abs for 14 h. CRTAM expression was analyzed by flow cytometry. The numbers indicate the percentages of CRTAM⁺ and CRTAM⁻ population among CD4⁺ CD69⁺ T cells. (B) Protein expression of CTL-related genes in CRTAM⁺ CD4⁺ T cells residing in the lung. (C) Influenza-specific cytotoxicity by lung CD4⁺ T cells from virus-infected mice. Lung CD4⁺ T cells from WT and CRTAM-KO mice were analyzed for influenza-specific cytotoxicity against NP-peptide pulsed LPS-activated B cells as the target. Representative FACS profiles of cytotoxic analysis are shown by PI-staining of dead cells at E:T ratio 40:1 (left), and specific cytotoxicity at various E:T ratios (right). The numbers indicate the percentages of PI⁺ dead cells. (D) CRTAM⁺ CD4⁺ T cells in the intestine. CD4⁺ T cells from the spleen and intestinal lamina propria (LP) were unstimulated (left) or simulated with anti-CD3/CD28 Abs (middle) for 14 h. Experimental colitis was induced by transferring naive CD4⁺ T cells into RAG-deficient mice. CD4⁺ T cells from colonic LP (cLP) and intraepithelial lymphocyte (cIEL) in colitis-induced mice (right). CRTAM expression was quantified by flow cytometry. The numbers indicate the percentages of CRTAM⁺ and CRTAM⁻ population among CD4⁺CD25⁺ T cells. (E) CRTAM expression in CADM1-deficient mice. CRTAM expression was analyzed on T cells from iLP of CADM1^+/− and CADM1^−/− mice after stimulation (left). CRTAM–CADM1 interaction influences on effector memory differentiation (right). The numbers indicate the percentages of CRTAM⁺ cells (left) or CD62L⁺ cells (right). (F) Time course of body weight loss under colitis induction. Naive CD4⁺ T cells from CRTAM-deficient (KO), CRTAM-heterozygous (Het) mice (or no transfer control) were transferred into RAG-deficient mice. Body weight loss was measured every week. (G) Colitis induction in Granzyme B–deficient mice. Naive CD4⁺ T cells prepared from gzmB-KO or WT mice were transferred into RAG-deficient mice. The results shown are representative of at least two independent experiments. Statistical significance was determined by a two-tailed unpaired Student’s t test. Error bars are SD. *, P < 0.05; **, P < 0.01; ***, P < 0.001.