The trial confirmed a low expression of the leukaemia inhibitory factor (LIF), interleukin 11 (IL-11R), and a decreased level of the enzyme involved in the synthesis of endometrial ligand for L-selectin in eutopic endometrium in the group of infertile women with endometriosis, compared with the fertile control group [92,93,94,95]. The gene discussed is SELL; the disease is endometriosis.