CD8+ T cells without CTLA4 expression result in significantly higher IFN-gamma and granzyme B production and enhanced cytolysis in an animal model, which can be in concordance with significantly higher CTLA4 antigen expression among CTLA4 T cells in the serum of patients with endometriosis, with a positive correlation of the percentage of CD4+ and CD8+ T cells and the endometriosis stage [28]. This evidence concerns the gene CD4 and endometriosis.