Karthikeyan et al. also found the IFNG gene to be differentially expressed in both early and late stage ulcers in human FK, and correlated this to the presence of CD3+ and CD4+ cells in the immunohistochemical analysis of late stage ulcers, implying a Th1 response (Karthikeyan et al., 2011). This evidence concerns the gene CD4 and ulcer disease.