On the cover: Image of TCRβ CDR3 sequences from CD4⁺ T cells isolated from immunized Gucy2c^−/− mice and enriched for GUCY2C_153–167 specificity. Each bubble corresponds to a unique CDR3 sequence (by amino acid) and bubble size indicates the frequency of reads. Abraham, T. S., J. C. Flickinger, Jr., S. A. Waldman, and A. E. Snook. 2019. TCR retrogenic mice as a model to map self-tolerance mechanisms to the cancer mucosa antigen GUCY2C. J. Immunol. 202: 1301–1310.