EXPRESSION OF C-KIT AND KIT-LIGAND PROTEINS IN NORMAL HUMAN TISSUES

The c-kit receptor and its cognate ligand, KL, play a critical role in melanogenesis, gametogenesis, and hematopoiesis. Studies on the expre ssion of c-kit and KL have been primarily focused on mouse development . We undertook the present study to characterize the pattern of expres sion of these molecules in normal adult human tissues. Using immunohis tochemistry and consecutive tissue sections from the same block, we ev aluated a variety of well-preserved normal tissues for c-kit and KL mi croanatomic distribution. c-kit protein was identified in tissue mast cells, melanocytes, glandular epithelial cells of breast, parotid, der mal sweat, and esophageal glands. Scattered c-kit immunoreactivity was also observed for testicular and ovarian interstitial cells. A striki ng regional distribution of c-kit was detected in the central nervous system, particularly in the cerebellum, hippocampus, and dorsal horn o f the spinal cord. KL protein was identified in cells complementary to staining for the receptor, such as glandular myoepithelium of breast and sweat glands. Intense KL immunoreactivity was observed in smooth m uscle cells of the bladder, cervix, uterus, and gastrointestinal tract , as well as in striated and cardiac muscle. Strong KL staining was al so detected in prostate fibromuscular stroma cells. In the central ner vous system, KL expression was confined to Golgi and Purkinje cells in the cerebellum. These results suggest a role for this receptor and it s ligand in the maintenance of a variety of fully differentiated tissu es.