THE IMMUNE-RESPONSE AND THE EYE - TCR ALPHA-CHAIN RELATED MOLECULES REGULATE THE SYSTEMIC IMMUNITY TO ANTIGEN PRESENTED IN THE EYE

Injection of antigen into the anterior chamber (AC) of the eye results in the induction of immune deviation in which antibody production is activated and delayed-type hypersensitivity (DTH) is inhibited. This s ystem is termed anterior chamber associated immune deviation (ACAID) a nd the model is used to examine certain aspects of the immunologic pri vilege of the eye. Recent studies have established that following anti gen presentation in the eye, an 'ACAID-inducing' signal is produced th at directly enters the blood. This signal then homes to the spleen whe re T cells that down-regulate DTH are activated. For many antigens thi s 'ACAID signal' is a soluble protein released within 2 days of AC inj ection. Although the presence of this molecule (or molecules) has been described using several antigens, the exact nature of the soluble med iator has escaped characterization. We have further explored the natur e of this signal using HSV-1-induced immune deviation. Our results sho w the soluble 'signal' was released by T cells that encounter antigen in the ocular microenvironment. This mediator was antigen specific, co ntained TCR alpha-chain (but not the TCR beta-chain) determinants and had an apparent molecular weight of 46 kDa. These results show that th e release of soluble TCR alpha-chain from sites of T cell interaction within the microenvironment of the eye can regulate systemic immune re sponses. These results have implications for the control of immune res ponse that might be damaging to organs such as the eye.