Alpha 6 integrin distribution in human embryonic and adult tissues.

Alpha 6 integrin is an adhesion molecule that connects cells with extracellular matrix molecules of the laminin family. The laminin interaction seems to be essential for cell differentiation during embryogenesis and for the subsequent maintenance of tissue integrity in the adult. Alpha 6 integrin can also interact with laminin-independent cellular ligands and in this way plays a role in homing of leucocytes. Furthermore, in cancer biology alpha 6 integrin has an important role in metastasis and as a possible new prognostic factor; exact knowledge of alpha 6 integrin distribution in normal human tissues is therefore a crucial element. By immuno-histochemical methods we have screened alpha 6 integrin expression of representative human tissues from the adult and the embryonic organism. All tested epithelia were alpha 6 integrin positive, except for the endocrine cells of the pancreas and the adrenal glands. Heterogeneous staining was found on non-epithelial tissues. Strong staining was evident in peripheral nerves (Schwann cells), germ and Sertoli cells, endothelia, and smooth muscle cells of the myometrium. Weak staining was found in nerve cells of the stratum granulosum, the microglia, Kupffer's cells and stromal cells of the ovary. All fibroblasts, striated muscle cells and astrocytes were negative. The tissue distribution of alpha 6 integrin and the semi-quantitative estimation of their expression level should provide a better understanding of alpha 6 integrin function under normal and pathological conditions, in particular in tumour progression.