Abstract:
To examine differences in severity of experimental autoimmune uveitis (EAU) in wild–type pigmented C57BL/6 mice and C57BL/6 mice with a spontaneous mutation in the tyrosinase gene, resulting in albinism.
Wild–type and tyrosinase mutant C57BL/6 mice were obtained from Jackson Laboratories. Mice were induced for EAU using 500µg per animal of a peptide consisting of amino acids 1–20 of human interphotoreceptor retinoid binding protein (IRBP) in complete Freund’s adjuvant supplemented with Mycobacterium tuberculosis strain H37RA (5 mg), and concurrently given 1.5 mg of purified Bordetella pertussis toxin intraperitoneally. Eyes were collected from humanely euthanized mice on day 21 after immunization. Eyes were placed in OCT and snap–frozen at –80°C. Serial sections (10 µm) of each eye were obtained and stained with hematoxylin–eosin. EAU was graded on an ordinal 4–point scale in a masked fashion. Statistical analyses (Student’s t–test and Chi–square test) were carried out to determine the significance of differences in average severity score and disease incidence for animals in the pigmented versus albino groups.
Wild type pigmented mice developed EAU at an incidence of 86% (12/14) while albino mice developed EAU with a 100% incidence. However, the average severity of EAU was significantly less in albino mice compared with wild type mice (Table).
Previous studies have suggested both a proinflammatory and antiinflammatory function for melanin. In the current study, albino mice developed EAU at a significantly lower severity than did pigmented wild type mice, supporting the concept that the presence of melanin may have an enhancing effect on EAU.
Keywords: uveitis-clinical/animal model • autoimmune disease