Abstract: |
A primary goal of cancer immunotherapy is to improve the naturally occurring, but weak, immune response to tumors. Ineffective responses to cancer vaccines may be caused, in part, by low numbers of self-reactive lymphocytes surviving negative selection. Here, we estimated the frequency of CD8 (+) T cells recognizing a self-antigen to be <0.0001% (∼1 in 1 million CD8(+) T cells), which is so low as to preclude a strong immune response in some mice. Supplementing this repertoire with naive antigen-specifc cells increased vaccineelicited tumor immunity and autoimmunity, but a threshold was reached whereby the transfer of increased numbers of antigen-specifc cells impaired functional beneft, most likely because of intraclonal competition in the irradiated host. We show that cells primed at precursor frequencies below this competitive threshold proliferate more, acquire polyfunctionality, and eradicate tumors more effectively. This work demonstrates the functional relevance of CD8(+) T cell precursor frequency to tumor immunity and autoimmunity. Transferring optimized numbers of naive tumor-specifc T cells, followed by in vivo activation, is a new approach that can be applied to human cancer immunotherapy. Further, precursor frequency as an isolated variable can be exploited to augment effcacy of clinical vaccine strategies designed to activate any antigen-specifc CD8(+) T cells. © 2009 Rizzuto et al. |
Keywords: |
nonhuman; antineoplastic agent; neoplasm; neoplasms; cd8 antigen; cd8+ t lymphocyte; cd8-positive t-lymphocytes; mouse; animal; animals; mice; cell division; melanoma; spleen; skin neoplasms; in vivo study; pathology; radiation exposure; skin tumor; immunology; immune response; immunotherapy; pre t lymphocyte; vaccination; experimental melanoma; melanoma, experimental; autoantigen; autoantigens; tumor immunity; autoimmunity; lymphocyte antigen receptor; receptors, antigen, t-cell, alpha-beta; antigens, cd8
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