Release of complement regulatory proteins from ocular surface cells in infections

The decay accelerating factor (DAF or CD55) and the membrane inhibitor of reactive lysis (MIRL or CD59), two complement regulatory proteins that protect self cells from autologous complement-mediated injury, are attached to corneal and cqonjunctival epithelial cells by glycosylphos-phatidylinositol (GPI) anchors. We sought to 1) determine the frequency with which bacteria recovered from patients with infections of the eye elaborate factors that can remove these surface proteins from ocular cells, 2) determine the spectrum of bacteria from other sites that have similar effects, and 3) establish the time interval required for reconstitution of the two regulators.

Culture supernatants of 18 ocular isolates [P. aeruginosa (n = 3), S. marcescens (n = 1), S. epidermidis (n = 9), and S. aureus (n = 5)], and > 100 other clinical specimens isolated in the hospital's microbiology laboratory [P. mirabilis (n = 1), S. aureus (n = 65), S. epidermidis (n = 24), B. cereus (n = 12), H. influenzae (n = 15), and Enterobacter sp. (n = 21)] were incubated at 37 degrees C for various times with conjunctival epithelial cells, conjunctival fibroblasts or HeLa cells and the release of DAF and CD59 proteins from the surfaces of the cells analyzed by 2-site immunoradiometric assays and by Western blotting. The kinetics of recovery of DAF and CD59 expression on the cells was measured by flow cytometry.

DAF and/or CD59 release from the cell monolayers varied from < 5% to > 99% at as much as a 1:81 dilution of the supernatant from some bacteria. On conjunctival epithelial cells, more than 8 hr was required for 44% recovery of DAF expression and for 50% recovery of CD59 expression.

Bacteria produce phospholipases and/or other enzymes which can efficiently remove DAF and CD59 from ocular cell surfaces. This phenomenon may correlate with their in vivo pathogenicity.