Abstract
Purpose:
Both conjunctivas are regarded as immunologically independent from each other, but there is anecdotal evidence that one ocular surface might condition its fellow. The purpose of this work was to evaluate the effect that a corneal lesion on one eye exerts over the conjunctival immune response of the opposite eye and the potential mechanisms involved.
Methods:
An unilateral controlled chemical burn with NaOH was induced in the cornea of 8-week-old female Balb/c mice (day 1, 3 animals/group, n=4), which were then instilled ovalbumin (OVA) daily (days 2-5) either in the same or the fellow eye. Mice were then immunized with OVA in adjuvant (day 8) and their T cell responses were measured by delayed-type hypersensitivity (DTH) assays in the footpads (day 15). Some mice underwent unilateral superior cervical sympathectomy one week before corneal burn. To assess lymphatic drainage pathways, fluorescent OVA was injected in the subconjunctival space of one eye and 2 hours later each cervical lymph node was separately harvested.
Results:
OVA instillation in one eye of uninjured mice blunted the DTH response (51±10%, p<0.05), while instillation after corneal burn did not reduce it when done either in the injured (86±7%, ns) or in the fellow eye (83±6%, ns). Regarding lymphatic drainage, fluorescent OVA was detected in homolateral (p<0.001) but not in contralateral submandibular and preauricular lymph nodes. However, T cell activation was observed in both homo- (+42% CD69+ and +22% CD25+ cells, p<0.05) and contralateral (+31% CD69+ and +23% CD25+ cells, p<0.05) lymph nodes 48 h after corneal injury. Unilateral sympathectomy did not prevent conditioning of the conjunctival response by the contralateral corneal burn, but instead enhanced the DTH response after ocular OVA instillation on the operated side (p<0.05).
Conclusions:
A unilateral corneal lesion is able to tip the immune balance of the contralateral eye despite the absence of direct chemical damage or crossed lymphatic drainage. Nevertheless, T cell activation in the opposite lymph nodes shows that the local immune response is indeed affected. Sympathetic nerve terminals apparently exert an inhibitory immune influence on the conjunctiva but are not involved in eye-to-eye immune crosstalk. These results altogether suggest that both ocular surfaces are immunologically interdependent.