DISTRIBUTION OF LEUKOCYTES IN THE EPITHELIUM AND INTERSTITIUM OF 4 REGIONS OF THE LEWIS-RAT EPIDIDYMIS

Background: Leukocytes expressing different surface markers were studi ed in four regions of the epididymis of Lewis rats, Cells resembling l ymphocytes or monocytes had been described in the epididymis, but prev ious studies differed as to their nature and immunologic significance, Methods: Frozen sections were immunocytochemically stained with monoc lonal antibodies W3/25, OX-8, OX-42, and RLN-9D3, which are directed t oward markers on CD4+ cells, CD8+ cells, macrophages, and B lymphocyte s, respectively, The concentration of stained cells in the epithelium and interstitial tissue of the initial segment, caput, proximal cauda, and distal cauda regions was determined by a procedure based on the o ptical disector method, Results: CD4+ leukocytes were present in great er concentration than CD8+ cells or macrophages in both the epithelium and interstitial tissue of all four regions, In the epithelium, the c oncentration of CD8+ leukocytes was greater than that of macrophages i n the initial segment, caput, and distal cauda, In the interstitium, h owever, the concentration of macrophages exceeded that of CD8+ cells i n both parts of the cauda, Macrophages and T lymphocytes were generall y present in greater concentrations in the interstitium than in the ep ithelium, especially in the more proximal parts of the epididymis, In contrast to T cells, B lymphocytes were not detected in the interstiti um or epithelium of any of part of the epididymis, despite prominent s taining of B cells in other locations, Conclusions: The epididymal epi thelium of the Lewis rat contains many T lymphocytes, which may corres pond to 'halo' cells, CD4+ leukocytes predominate in all regions of th e epididymis, The interstitium may function as a reservoir of leukocyt es for the epithelial compartment. The epididymis is not normally a si te for local immunoglobulin synthesis. (C) 1997 Wiley-Liss, Inc.