Antigen-specific depletion of CD4+ T cells by CAR T cells reveals distinct roles of higher- and lower-affinity TCRs during autoimmunity.

Both higher- and lower-affinity self-reactive CD4⁺ T cells are expanded in autoimmunity; however, their individual contribution to disease remains unclear. We addressed this question using peptide-MHCII chimeric antigen receptor (pMHCII-CAR) T cells to specifically deplete peptide-reactive T cells in mice. Integration of improvements in CAR engineering with TCR repertoire analysis was critical for interrogating in vivo the role of TCR affinity in autoimmunity. Our original MOG_35–55 pMHCII-CAR, which targeted only higher-affinity TCRs, could prevent the induction of experimental autoimmune encephalomyelitis (EAE). However, pMHCII-CAR enhancements to pMHCII stability, as well as increased survivability via overexpression of a dominant-negative Fas, were required to target lower-affinity MOG-specific T cells and reverse ongoing clinical EAE. Thus, these data suggest a model in which higher-affinity autoreactive T cells are required to provide the "activation energy" for initiating neuroinflammatory injury, but lower-affinity cells are sufficient to maintain ongoing disease. Engineering CAR T cells to target autoimmunity: Autoimmune diseases including multiple sclerosis (MS) are driven by pathogenic CD4⁺ T cells that recognize self-antigens. Yi et al. engineered chimeric antigen receptor (CAR) T cells to recognize and kill self-reactive T cells by introducing a peptide-MHCII (pMHCII) domain. Their original pMHCII-CAR design efficiently deleted T cells bearing a higher-affinity T cell receptor, whereas further modifications to enhance pMHCII stability and in vivo survival enabled simultaneous targeting of lower-affinity T cells. In a mouse experimental autoimmune encephalomyelitis model of MS-like disease, deletion of higher-affinity T cells was sufficient to prevent disease onset, whereas targeting lower-affinity T cells was necessary to reverse ongoing disease. These findings highlight strategies for designing CAR T cells to target distinct stages of autoimmune disease. [ABSTRACT FROM AUTHOR]