Immuno-competent cells in the murine epididymis following infection with Escherichiu coli

Epididymitis was induced by retrograde injection of Escherichia coli into the vas deferens of 28 mice. A group of 28 saline-injected animals served as controls. On Days 1, 3, 7 and 28, groups of seven animals were killed. Bacterial culture was performed. Leucocyte numbers and distribution were determined in epididymides.
In infected mice, E. coli were isolated from all epididymides on Days 1 and 3, but only from five of seven epididymides on Days 7 and 28. One week after infection, the total number of macrophages rose from about 10 to 28%. Significantly increased macrophage percentages were also found in animals killed 28 days after infection. A simultaneous increase in MHC class II positive cells was seen on Day 7. A total of 20% of the cells expressed MHC class II in infected epididymides (normal = 6%). A similar increase was found on Day 28 after infection. Most of the macrophages and MHC class II positive cells were located in the interstitium, fewer in the peritubular layer and nearly none in the epithelium. The main increase in these cells occurred in the interstitium and, to a lesser but significant extent, in the peritubular area.
T-helper and T-suppressor/cytotoxic lymphocytes reached peak values on Day 28. The increase in T-lymphocytes and simultaneous appearance of plasma cells follo wed the increase in numbers of macrophages and MHC class II positive cells. They were located mainly in the interstitium. A sequential increase in leucocyte subsets and negative culture results for E. coli were observed on Days 7 and 28 (2/7 on each day). The inflammatory process was restricted to the interstitium.
It is concluded that stimulation of T-lymphocytes and plasma cells by macrophages/MHC class II positive cells acts as an effective immune response to E. coli in the epididymal interstitiurn.