HLA-B27 transgenic Lewis rats and iritis after gram negative infection

Purpose: Humans with the HLA-B27 gene are predisposed to iritis, as can follow gram-negative infection. The availability of HLA-B27 transgenic rats allowed us to examine if the presence of this gene influenced susceptibility to iritis. Methods: HLA-B27 transgenic (21-4L line; 6 copies/cell) and wild type rats (200-400g) were challenged subcutaneously with E Coli Lipopolysaccharide (LPS) (N=85) or intravenously with Salmonella enteritidis (10⁴ or 10⁶ cfu/animal; N=12/dose) or Yersinia enterocolitica O:3 (10⁶ cfu; N=8). Iritis was evaluated by slit lamp examination and in selected eyes by histology. Results: LPS caused iritis within 24 hrs in 99% of rats and was bilateral in 92%. Live bacteria induced iritis in 70% of animals which began 7-9 days post innoculum, was unilateral in 75% of rats at 10⁴ cfu and 16% at 10⁶ cfu, was equally common in males and females and usually resolved by 6 days but sometimes recurred. At 10⁶ cfu, 11 of 12 rats died by day 9, whereas at 10⁴ cfu survival was up to 20 days. Histology confirmed iritis after bacterial infection and indicated that most inflammatory cells were mononuclear. Conclusion: The presence of HLA-B27 did not appear to influence the incidence or severity of iritis, after either LPS or bacterial infection. The timing and unilaterality of iritis after bacterial infection distinguished it from LPS-induced iritis. This experimental system offers a unique model to clarify the relation between gram-nepative bacteria or their products and iritis.