Laminin subtype distribution in the human ciliary body.

PURPOSE: Laminin is a family of heterotrimeric molecules each consisting of a heavy chain (A or M chain), and two light chains (B1, B2, or S chains). In this study the distribution of these chains was determined in human ciliary body.

METHOD: Tissue slices from five postmortem eyes were incubated with monoclonal antibodies against the chains and with a fluorescent secondary antibody. After the tissues were embedded in Spurr's resin, 1-micron thick sections were obtained.

RESULTS

Uniform staining with A, S, and B2 laminin chains was observed in basement membrane surrounding muscle bundles. Inside the bundles, the basement membrane around individual fibers was evenly stained by S and B2; however, only some fibers had A-chain immunoreactivity. The basement membrane of blood vessels was also stained with A, S, and B2. Stromal connective tissue was not stained. Ciliary pigmented epithelium basement membrane demonstrated A, S, and B2 immunoreactivity, but not B1 immunoreactivity. Adjacent to the nerves, M, S, B1, and B2 immunoreactivity was detected.

CONCLUSION

The results indicate that A-S-B2 laminin is present in the basement membranes associated with smooth muscle bundles, blood vessels, and the nonpigmented and pigmented epithelia. A-B1-B2 laminin is also found in the pigmented epithelium basement membrane. M-B1-B2 and M-S-B2 are found in association with nerve tissue. This heterogeneity in the basement membranes of the ciliary body suggests that they mediate different cellular functions.