A caveat for T cell transfer studies: generation of cytotoxic anti-Thy1.2 antibodies in Thy1.1 congenic mice given Thy1.2+ tumors or T cells.

Thy1.1 congenic B6.PL mice were used to simultaneously monitor Thy1.2+ E.G7-OVA tumors transplanted in the a.c. of the eye and i.v.-transferred tumor-specific Thy1.2+ CTLs to determine mechanisms that inhibit the tumoricidal activity of CTL responses in mice with established ocular tumors. Transferred CTLs were systemically deleted in mice with established ocular tumors. However, this deletion was not a unique mechanism of immune evasion by ocular tumors. Rather, development of Thy1.2+ tumors in the eye or skin of B6.PL mice generated cytotoxic anti-Thy1.2 antibodies that eliminated a subsequent Thy1.2+ T cell transfer. Anti-Thy1.2 immune responses in B6.PL mice were influenced by the route of antigen administration, as the serum concentration of cytotoxic anti-Thy1.2 antibodies was 92-fold greater in mice with eye tumors in comparison with mice with skin tumors. In addition, anti-Thy1.2 immune responses were detected in B6.PL mice given naïve Thy1.2+ T cells i.p. but not i.v. Anti-Thy1.2 responses were augmented in B6.PL mice with ocular Thy1.2+ EL-4 tumors that did not express OVA, suggesting immunodominance of OVA antigen over Thy1.2. Thy1.1+ T cells given i.p. was not immunogenic in Thy1.2 congenic mice. These data reaffirm that the introduction of antigens in the a.c. induces robust antibody responses. Experimentation using allotypic differences in Thy1 between donor cells and recipient mice must consider cytotoxic anti-Thy1 antibody generation in the interpretation of results.