Comparison of anti-tumor responses against TL positive lymphoma induced by skin grafting and dendritic cell immunization

Immunity against mouse thymus-leukemia antigen (TL) protects against development of lymphomas induced by a chemical carcinogen, N-butyl-N-nitrosourea

Mouse thymus-leukemia antigens (TL) are aberrantly expressed on T lymphomas in C57BL/6 (B6) and C3H/He (C3H) mice, while they are not expressed on normal T lymphocytes in these strains. When N-butyl-N-nitrosourea (NBU), a chemical carcinogen, was administered orally to B6 and C3H strains, lymphoma development was slower than in T3(b)-TL gene-transduced counterpart strains expressing TL ubiquitously as self-antigens, suggesting that anti-TL immunity may play a protective role. In addition, the development of lymphomas was slightly slower in C3H than in B6, which seems to be in accordance with the results of skin graft experiments indicating that both cellular and humoral immunities against TL were stronger in C3H than B6 mice. The interesting finding that B lymphomas derived from a T3(b)-TL transgenic strain (C3H background) expressing a very high level of TL were rejected in C3H, but not in H-2K(b) transgenic mice (C3H background), raises the possibility that TL-specific effector T cell populations are eliminated and/or energized to a certain extent by interacting with H-2K(b) molecules.

Thymus-leukemia antigen (TL) as a major histocompatibility complex (MHC) class Ib molecule and tumor-specific antigen

Mouse thymus-leukemia antigens (TL) belong to the family of major histocompatibility complex (MHC) class Ib antigens and have a unique mode of expression, i.e., in contrast to other MHC class Ib or Ia antigens, they are found restricted to the intestines in all mouse strains, but also in the thymus of certain strains (TL(+) strains). Nevertheless, a proportion of T lymphomas/leukemias in strains that do not express TL in the thymus (TL(-) strains) feature TL as a tumor antigen. TL was originally defined serologically, but subsequently we have succeeded in generating T cell receptor (TCR) and cytotoxic T lymphocytes (CTL) recognizing TL. By use of TL tetramers free from peptides and transfectants expressing various TL/H-2 chimeric molecules, we have been able to show that TL-specific CTL recognize the alpha1/alpha2 domain of TL without any additional antigen molecules. We previously reported that one of TL's functions in the thymus is positive selection of TCR CTL. Recent studies with TL tetramers revealed that they can bind to normal intestinal intraepithelial lymphocytes (iIEL) and thymocytes in a CD8-dependent, but TCR/CD3-independent manner, while their binding to TL-specific CTL is TCR/CD3- and CD8-dependent. The possible significance of these findings in relation to the roles of TL in the intestines is discussed. We have long been interested in TL as a model tumor antigen which shares characteristics with human differentiation tumor antigens, and we have demonstrated that growth of TL(+) lymphoma cells in vivo is suppressed by immunization with TL(+) skin or dendritic cells (DC) from TL transgenic mice. In addition, anti-tumor effects against TL(+) T lymphomas were obtained by adoptive transfer of TL tetramer strongly-positive TL-specific CTLs.

The binding of thymus leukemia (TL) antigen tetramers to normal intestinal intraepithelial lymphocytes and thymocytes

Thymus leukemia (TL) Ags belong to the family of nonclassical MHC class I Ags and can be recognized by both TCRalphabeta and TCRgammadelta CTL with TL, but not H-2 restriction. We previously reported that the CTL epitope is TAP independent, but the antigenic molecule(s) presented by TL has yet to be determined. In the present study, TL tetramers were prepared with T3(b)-TL and murine beta(2)-microglobulin, not including antigenic peptides, and binding specificity was studied. CTL clones against TL Ags were stained with the T3(b)-TL tetramer, and the binding shown to be CD3 and CD8 dependent. Normal lymphocytes from various origins were also studied. Surprisingly, most CD8(+) intraepithelial lymphocytes derived from the small intestines (iIEL), as well as CD8(+) and CD4(+)CD8(+) thymocytes, were stained, while only very minor populations of CD8(+) cells derived from other peripheral lymphoid tissues, such as spleen and lymph nodes, were positive. The binding of T3(b)-TL tetramers to CD8(+) iIEL and thymocytes was CD8 dependent, but CD3 independent, in contrast to that to TL-restricted CTL. These results altogether showed that TL-restricted CTL can be monitored by CD3-dependent binding of T3(b)-TL tetramers. In addition, CD3-independent T3(b)-TL tetramer binding to iIEL and thymocytes may imply that TL expressed on intestinal epithelium and cortical thymocytes has a physiological function interacting with these tetramer(+)CD8(+) T lymphocytes.