Purpose: A prior investigation has demonstrated that innate immune-specific cytokines are enriched in idiopathic orbital inflammation (IOI). To further document the role of innate immunity in IOI, the authors sought to determine whether toll-like receptors (TLRs) are present in biopsy specimens of this disorder.
Methods: Immunohistochemical staining for TLR2, TLR3, and TLR4 was performed on biopsy specimens taken from patients with IOI, and the number of TLR-positive cells was counted across five 40× light microscopic fields. These results were compared with an isotype control and with orbital adipose tissue taken from patients without evidence of inflammation.
Results: All IOI specimens demonstrated positivity for all 3 TLRs, and sections stained for isotype controls did not demonstrate any positivity. Furthermore, orbital adipose tissue did not demonstrate any significant signal. The mean number of positive cells was 24.4 cells/high power field (hpf; standard deviation = 11.6 cells/hpf), 7.23 cells/hpf (standard deviation = 5.59 cells/hpf), and 11.7 cells/hpf for TLR2, TLR3, and TLR4, respectively.
Conclusions: This study provides the first documentation of TLRs in orbital disease. Toll-like receptors are present in IOI, and IOI may represent an aberrant innate immune response. Interference with TLRs may represent an additional potential therapeutic mechanism in the management of IOI.