Testicular expression of SP-A, SP-D and MBL-A is positively regulated by testosterone and modulated by lipopolysaccharide

Pattern recognition proteins viz., Surfactant Protein-A (SP-A), Surfactant Protein-D (SP-D) and Mannan Binding Lectin-A (MBL-A) regulate inflammatory immune responses. In view of their plausible contribution to immune privilege in testis, the present study explored their expression and regulation in murine testis. The testicular expression of SP-A, SP-D and MBL-A significantly increased at puberty and was significantly down-regulated in testosterone suppression model. Of the isolated germ cells, Sertoli cells, myoid cells and Leydig cells, germ cells expressed SP-A, SP-D and MBL-A while myoid cells were found to express MBL-A. SP-A and SP-D were localised on head and tail of murine caudal sperm, whereas MBL-A was observed on the connecting piece and tail. Systemic lipopolysaccharide challenge significantly up-regulated SP-A and SP-D levels in murine testis after 24 h. Positive regulation of collectins by testosterone and their modulation in response to inflammation implicates their involvement in testicular immune-privilege.