Analysis of the functional WT1-specific T-cell repertoire in healthy donors reveals a discrepancy between CD4+ and CD8+ memory formation

The Wilms' tumour-1 (WT1) protein is considered a prime target for cancer immunotherapy based on its presumptive immunogenicity and widespread expression across a variety of malignancies. However, little is known about the naturally occurring WT1-specific T-cell repertoire because self-derived antigens typically elicit low frequency responses that challenge the sensitivity limits of current detection techniques. In this study, we used highly efficient cell enrichment procedures based on CD137, CD154, and pHLA class I tetramer staining to conduct a detailed analysis of WT1-specific T cells from the peripheral blood. Remarkably, we detected WT1-specific CD4(+) and CD8(+) T-cell populations in the vast majority of healthy individuals. Memory responses specific for WT1 were commonly present in the CD4(+) T-cell compartment, whereas WT1-specific CD8(+) T cells almost universally displayed a naive phenotype. Moreover, memory CD4(+) and naive CD8(+) T cells with specificity for WT1 were found to coexist in some individuals. Collectively, these findings suggest a natural discrepancy between the CD4(+) and CD8(+) T-cell lineages with respect to memory formation in response to a self-derived antigen. Nonetheless, WT1-specific T cells from both lineages were readily activated ex vivo and expanded in vitro, supporting the use of strategies designed to exploit this expansive reservoir of self-reactive T cells for immunotherapeutic purposes.