Analysis of intestinal intraepithelial lymphocytes (IELs) in the large intestine of T. muris-infected resistant BALB/c and susceptible AKR mice have shown that at the time of expulsion (around day 21 post infection) BALB/c mice have increased numbers of CD4+ IELs whereas IELs in AKR animals are predominantly CD8+ [26]. The gene discussed is CD4; the disease is infection.