Major histocompatibility complex (MHC) class I molecules associate with a variety of peptide ligands during biosynthesis and present these ligands on the cell surface for recognition by cytotoxic T cells. We have designed conditional MHC ligands that form stable complexes with MHC molecules but degrade on command, by exposure to a defined photostimulus. 'Empty MHC molecules' generated in this manner can be loaded with arrays of peptide ligands to determine MHC binding properties and to monitor antigen-specific T-cell responses in a high-throughput manner. We document the value of this approach by identifying cytotoxic T-cell epitopes within the H5N1 influenza A/Vietnam/1194/04 genome.

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Adoptive transfer of T-cell receptor (TCR) genes has been proposed as an attractive approach for immunotherapy in cases where the endogenous T-cell repertoire is insufficient. While there are promising data demonstrating the capacity of TCRmodified T cells to react to foreign antigen encounter, the feasibility of targeting tumor-associated self-antigens has not been addressed. Here we demonstrate that T-cell receptor gene transfer allows the induction of defined self-antigenspecific T-cell responses, even when the endogenous T-cell repertoire is nonreactive. Furthermore, we show that adoptive transfer of T-cell receptor genes can be used to induce strong antigen-specific T-cell responsiveness in partially MHCmismatched hosts without detectable graft versus host disease. These results demonstrate the feasibility of using a collection of "off the shelf" T-cell receptor genes to target defined tumor-associated self-antigens and thereby form a clear incentive to test this immunotherapeutic approach in a clinical setting. IntroductionMajor histocompatibility complex (MHC) molecules present peptides on the cell surface irrespective of whether they are derived from foreign proteins or from self-proteins. Different tissue types within the body each express a unique set of proteins, and peptide epitopes derived from such tissue-specific proteins can in principle be used as tumor-rejection antigens. 1 However, because most of these tumor-associated antigens (TAAs) are nonmutated selfantigens, the T-cell repertoire specific for such antigens is generally small in size and low in avidity. Indeed, both preclinical studies and clinical trials have provided evidence that a lack of T cells with the required reactivity is a major factor limiting T-cell-based immunotherapy. For instance, murine studies have demonstrated that tumor-specific T-cell responses against foreign tumor-associated antigens can readily be induced by vaccination. However, when the same tumor-associated antigen is considered "self" by the available T-cell repertoire, reactivity to these antigens is highly reduced. 2,3 In line with this, replacement of the endogenous T-cell compartment through a combination of allogeneic stem cell transplantation (allo-SCT) and donor lymphocyte infusion (DLI) forms an effective treatment strategy for patients with hematologic malignancies such as chronic myeloid leukemia (CML). 4 Importantly, the antileukemic effect of allo-SCT/DLI is dependent on the recognition of minor histocompatibility antigens (MiHAgs) of the recipient as "nonself" by the infused donor lymphocytes, and the development of T-cell responses against such antigens is predictive of remission. 5 The effects of DLI following allo-SCT provide an excellent example of how an endogenous antigen can become foreign by introduction of a novel T-cell compartment and how recognition of endogenous antigens by this exogenous T-cell compartment is associated with remission. The major drawback of this treatment protocol is that the introduced T-cell reactivity against self...

Our results suggest flow cytometric measurement of agonist-induced P-selectin expression can measure PLT quality decline over the entire range encountered during 10-day storage of both standard PLTs and Mirasol-treated PLTs in plasma.