The inflamed cauda epididymidis: a hub for ectopic lymphoid organ genesis

Infection and inflammation of the male reproductive tract are major factors leading to infertility. Insults targeting the epididymis are of concern as they can impair fertility. A considerable number of patients with epididymitis, even after antibiotic treatment, exhibit the presence of an epididymal infiltrate specifically in the cauda epididymidis and even suffer from infertility. For this reason, this study focused on investigating the cauda epididymidis at later time points from the infection in a well-established model of acute bacterial epididymitis as well as in an autoimmune model – experimental autoimmune epididymo-orchitis. We show that multiple elements associated with tertiary lymphoid organs formation, organization and maintenance are present in UPEC-infected as well as EAEO epididymidis compared to control cauda epididymidis. Overall design: Induction of experimental autoimmune epididymo-orchitis (EAEO) was performed as previously described (Nicolas et al., 2017). In brief, the mice were actively immunised with testicular homogenate prepared from decapsulated testes obtained from adult syngeneic mice, combined with adjuvant. The testicular homogenate was administered subcutaneously, 3 times, two weeks apart, together with an intraperitoneal injection of 100 ng Bordetella pertussis toxin (Calbiochem, Darmstadt, Germany). Complete Freund's adjuvant (Sigma-Aldrich, Saint Louis, USA) was used for the first immunisation, while incomplete Freund's adjuvant (Sigma-Aldrich) was used for subsequent immunisations. Control animals received either the respective adjuvant injections instead of testicular homogenate, or were left untreated. Animals were euthanized using carbon dioxide overdose, and tissues were collected at 30 and 50 days after the first immunisation. For RNA sequencing, the cauda epididymis from 4 mice from the experimental autoimmune orchitis group (E), and 4 mice from the Adjuvant treated group (A), and 3 mice from the control group (C) were selected.