CD106 (VCAM-1) IN TESTICULAR IMMUNOREGULATION

The expression of CD18, CD49d/CD29, CD44, CD54 and CD106 was studied i n the testis of normal mice at various ages, in the cryptorchid testis , in the testis of estrogen-treated mice and in the testis of non-obes e diabetic (NOD) mice, using immunocytochemistry to see which of these lymphocyte and endothelial adhesion proteins may be involved in lymph ocyte regulation in the testis. CD18-, CD49d/CD29-, CD44- and CD54-exp ressing cells were not found in the normal > 10-week-old BALB/c mouse testis. Leydig cells expressed CD106 strongly at this age. In contrast to the > 10-week-old testis, only very few interstitial cells of the 2-week-old normal mice expressed CD106. The expression of CD106 increa sed gradually with age so that at 6 weeks of age the expression of CD1 06 aias moderate in the interstitial tissue. In the experimentally abd ominal testis, CD106 was expressed in the interstitial tissue as stron gly as in the contralateral scrotal testis. CD44- and CD18-expressing cells were occasionally present in the interstitial tissue of the abdo minal testis, but not in the contralateral scrotal testis. CD54 was pr esent in the epithelium of the ductuli efferentes. In the testis of th e estrogen-treated mice, CD106 was expressed in the interstitial tissu e as strongly as in the normal mice. Occasional CD44- and CD18-express ing cells were found in the testicular capsule. In the testis of adult NOD mice, CD106 was present in the interstitial tissue, but none of t he other studied proteins. Immunoblotting of CD106 from the adult test is under reducing conditions demonstrated a single broad band with a M -r of 51-65 kDa. This is a novel isoform of CD106. In a modified Stamp er-Woodruff assay, lymphocytes bound to the testicular interstitial ti ssue. In co-incubations of native Leydig cells and lymphocytes. anti-C D106 antibodies prevented formation of Leydig cell-lymphocyte rosettes more than isotype-matched irrelevant control antibodies. suggesting t hat Leydig cell lymphocyte binding occurs through CD106-CD49d interact ions. In lymphocyte cultures in the presence of anti-CD3, aati-CD28. t he M-r > 5 K fraction of testis extract (containing CD106 as shown by immunoblotting) and anti-CD106 or control antibody, anti-CD106 did not consistently affect T cell H-3-TdR incorporation. The present results suggest that CD106 expressed by the Leydig cells may act as an adhesi on-promoting molecule or a co-stimulatory factor for T cells migrating to the testis. (C) 1997 Elsevier Science Ireland Ltd.