IMMUNE PRIVILEGE TO MHC-DISPARATE TUMOR GRAFTS IN THE ANTERIOR CHAMBER OF THE EYE

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Abstract
It has been suggested that immune privilege that is extended to tissues placed in the anterior chamber of the eye may not be absolute, implaying that a form of transient privilege may exist. We have studied the extent of immune privilege for histoincompatible tumor cells in the anterior chamber of the eye by using a modification of the limiting dilution analysis technique to quantitate the magnitude of tumor growth. It was found that immune privilege was absolute for minorhistoincompatible tumor cells inoculated into the anterior chamber of the eye. In this circumstance, tumor growth was unrestricted and quantitatively equivalent to tumor growth observed in the eyes of syngeneic mice. By contrast, immune privilege for MHC-incompatible tumor cells inoculated into the anterior chamber proved to be present, but transient. MHC-incompatible tumors grew within the anterior chamber of the eye during the first 12 days in a manner quantitatively indistinguishable from minor H tumors. However, these tumors were ultimately rejected, although survival of the tumor cells was prolonged and the maximum tumor mass achieved was larger than that observed for similar tumors injected subconjunctivally (a nonprivileged site). Early successful tumor growth was associated with impaired, alloantigen-specific delayed hypersensitivity, whereas rejection of the tumor coincided with the systemic emergence of specific DH. These results support the conclusion that immune privilege in the anterior chamber of the eye may be transient, rather than absolute, and that the critical determinant is whether a systemic state of tumor-specific DH can be affected.