Complement and polymorphonuclear leukocytes do not determine the vascular permeability induced by intraocular LPS.

Area of Science:

• Ophthalmology
• Immunology
• Inflammation Research

Background:

• Intravitreal injection of Escherichia coli endotoxin (LPS) induces ocular inflammation in rabbits.
• This inflammation involves increased ocular vascular permeability (OVP) and leukocyte infiltration, primarily polymorphonuclear leukocytes (PMNs).

Purpose of the Study:

• To investigate the roles of PMNs and complement in LPS-induced ocular inflammation and OVP.
• To characterize the chemotactic activity present in the aqueous humor during ocular inflammation.

Main Methods:

• Rabbits were treated with nitrogen mustard to deplete PMNs or with cobra venom factor (CVF) to deplete complement prior to LPS injection.
• Ocular vascular permeability was measured by 125I-albumin extravasation.
• Histopathology was used to assess leukocyte infiltration.
• Complement activity and chemotactic activity in serum and aqueous humor were measured.

Main Results:

• PMN depletion did not alter LPS-induced OVP.
• Complement depletion (using CVF) did not affect LPS-induced OVP, although it did affect a passive Arthus reaction.
• Chemotactic activity for rabbit PMNs was present in the aqueous humor of both control and CVF-treated rabbits and was not primarily C5a-mediated.

Conclusions:

• Neither circulating PMNs nor complement are the primary determinants of ocular vascular permeability following intravitreous LPS injection.
• The chemotactic activity in the aqueous humor during ocular inflammation is not mainly C5a and attracts rabbit PMNs.