1424 The role of immunologically cross-reactive antigens in the development of ocular onchocerciasis

Puroose Recurrent ocular toxoplasmosis is a major cause of blindness throughout the world. However, the pathogenetic mechanisms of reactivation of latent Toxoplasma gondii (T. gondii) infections are still unknqwn. An important question is whether the recurrent focal inflammatory responses in the retina are primarily directed against the parasite itself or whether autoimmune mechanisms play a role in the reactivations. Methods We designed a study to isolate and characterise the intraocular T cells involved in the recurrent inflammations. We tested a panel of T cell lines and T cell clones (TLCs) that have been derived from the vitreous of 7 patients with active recurrent ocular toxoplasmosis. w While no reactivity was found against retinal antigens, all T cell lines and 52 TLCs generated responded significantly to T. go&ii. The T. gondii-specific TLCs had the CD4+ phenotype, were generally HLA-DR restricted and displayed a heterogeneous T cell receptor usage. Conclusions Our findings suggest that the intraocular cellular immune response in recurrent ocular toxoplasmosis is predominantly T. gondii-specific. These observations are relevant not only to a further understanding of protective immunity and immunopathology but also may have implications for the design of effective vaccines.