Blood vessels of human islets of Langerhans are surrounded by a double basement membrane

Immunohistochemistry revealed a unique organization for human laminin-511/521 as a peri-islet BM, which co-invaginated into islets with vessels, forming an outer endocrine BM of the intra-islet vascular channels, and was distinct from the vascular BM that additionally contained laminin-411/421. These findings were verified by electron microscopy. Lutheran glycoprotein, a receptor for the laminin alpha5 chain, was found prominently on endocrine cells, as identified by immunohistochemistry and RT-PCR, whereas alpha(3) and beta(1) integrins were more diffusely distributed. High Lutheran content was also found on endocrine cell membranes in a short-term culture of human islets. The adhesion of dispersed beta cells to laminin-511 was inhibited equally effectively by antibodies to integrin and alpha(3) and beta(1) subunits and by the soluble Lutheran peptide.