Innate defence of the eye by antimicrobial defensin peptides
The surface of the eye is constantly exposed to environmental pathogens, and has several immunological and other defence features characteristic of the mucosal immune
system. The antimicrobial activity of the preocular tear film exceeds that of its known constituents. We postulate that a proportion of this excess is due to defensins, naturally occurring
antimicrobial peptides with activity against gram-positive and gram-negative bacteria, fungi and viruses.
A monoclonal antibody was used to detect alpha-defensins 1-3 in cryosections of conjunctiva and lacrimal gland, and in normal-tear immunoblots.
We found alpha-defensins 1-3 in inflamed conjunctiva (in relation to polymorphonuclear cells), lacrimal gland ductules, and in normal tears. RT-PCR showed a ß-defensin-1 message in cornea, conjunctiva, and lacrimal gland; and ß-defensin-2 message in cornea and conjunctiva but not lacrimal gland. alpha-defensins 5 and 6 were absent.
Purified or recombinant defensins may be useful treatments for eye infections because defensins have a broad spectrum of activity, are chemotactic for monocytes, accelerate wound healing, and may be non-antigenic, whereas most antibiotics have a comparatively limited spectrum of activity, interfere with healing due to ocular surface toxicity, and may produce allergic reactions.
RJ Haynes, PJ Tighe, HS Dua
The LANCET 1998; 352: 451-452