Lymphocyte subsets in conjunctival mucosa-associated-lymphoid-tissue afterexposure to retinal-S-antigen

Purpose : To evaluate the immune cell subsets in conjunctival mucosa-associ ated-lymphoid-tissue (C-MALT) following challenge with antigen. Methods : Ten adult female Lewis rats were studied. Five rats received one drop (5 mu L) of retinal S-antigen (500 mu g/mL in phosphate buffered salin e, PBS) instilled into the lower fornix twice daily for 10 consecutive days . Five rats received PBS only and served as controls for the experiment. Tw o days after the last instillation the animals were sacrificed and the orbi tal contents prepared for immunohistological staining. A panel of monoclona l antibodies was used: CD5, CD4, CD8, CD25, and CD45RA. The number of posit ive cells were counted in sections of epibulbar, forniceal, and tarsal conj unctiva. Results : There was a significant increase in the number of CD8(+) T lympho cytes in the conjunctiva of animals receiving retinal S-antigen when compar ed to control animals. Conclusion : Conjunctival instillation of retinal S-antigen causes an immun e response in the C-MALT with a significant increase in the CD8(+) T lympho cyte subset in this tissue. This response may be involved in the induction of tolerance to the encountered antigen.