T cells expressing antigen-specific T-cell receptors (TCRs) can mediate effective tumor regression, but they often also are accompanied by autoimmune responses. To determine the TCR affinity threshold defining the optimal balance between effective antitumor activity and autoimmunity in vivo , we used a unique self-antigen system comprising seven human melanoma gp100(209–217)-specific TCRs spanning physiological affinities (1–100 μM). We found that in vitro and in vivo T-cell responses are determined by TCR affinity, except in one case that was compensated by substantial CD8 involvement. Strikingly, we found that T-cell antitumor activity and autoimmunity are closely coupled but plateau at a defined TCR affinity of 10 µM, likely due to diminished contribution of TCR affinity to avidity above the threshold. Together, these results suggest that a relatively low-affinity threshold is necessary for the immune system to avoid self-damage, given the close relationship between antitumor activity and autoimmunity. The low threshold, in turn, indicates that adoptive T-cell therapy treatment strategies using in vitro-generated high-affinity TCRs do not necessarily improve efficacy.

IMPORTANCE Cutaneous immune-related adverse events (cirAEs) are some of the earliest toxic reactions to emerge following immune-checkpoint inhibitor (ICI) initiation. As an early indicator of robust inflammatory response, cirAEs may be associated with patterns of immune-mediated toxic effects, but associations between these events and noncutaneous immune-related adverse events (irAEs) remain underexplored.OBJECTIVES To characterize patterns of cirAEs and irAEs across care settings and examine associations between the features of first cirAE, overall irAE risk, and risk of specific irAE subtypes. DESIGN, SETTING, AND PARTICIPANTSA retrospective cohort study was conducted at a single academic medical center. The cohort included 358 patients with cancer who initiated anti-programmed death 1/ligand 1 and/or anticytotoxic-T-lymphocyte-4 ICI therapy between January 1, 2016, and March 8, 2019, and developed 1 or more cirAEs, identified using International Statistical Classification of Diseases and Related Health Problems, Tenth Revision codes and confirmed via manual medical record review. All relevant information documented before March 31, 2020, was included.EXPOSURES Anti-programmed death 1/ligand 1 and/or anticytotoxic-T-lymphocyte-4 therapy. MAIN OUTCOMES AND MEASURESAssociations between specific cirAE morphologic classes and patterns of irAEs (occurrence, timeline, organ class, and specific toxic effects). Given the potential that shared underlying factors are associated with the risk of both noncutaneous and cutaneous toxic effects, the presence of observed positive associations between certain cirAE and irAE subtypes was hypothesized. RESULTSOf the 358 patients, 213 were men (59.5%); median age was 65 years (interquartile range, 55-73 years). Nearly half of the patients (177 [49.4%]) with cirAE also developed a noncutaneous irAE. Most patients (128 [72.3%]) experienced their first cirAE before developing any irAE. Several cirAE morphologic classes were found to be associated with overall, organ-based, and specific irAEs. More specifically, mucositis was found to be associated with overall irAE risk (odds ratio [OR], 5.28; 95% CI, 1.11-24.26; P = .04), gastrointestinal irAEs (OR, 5.70; 95% CI,; P = .04), and the specific diagnosis of gastroenterocolitis (OR, 6.80; 95% CI, 1.24-37.39; P = .03). In addition, psoriasis was associated with an increased risk of endocrine irAEs (OR, 4.54; 95% CI, 1.21-17.04; P = .03). CONCLUSIONS AND RELEVANCEIn this cohort study, these findings underscore the risk of multisystem toxic effects in patients experiencing cirAEs and highlight potential opportunities for dermatologists in the management of noncutaneous toxic effects.

T cell receptors (TCRs) on T cells recognize peptide-major histocompatibility complex (pMHC) molecules on the surface of antigen presenting cells and this interaction determines the T cell immune response. Due to negative selection, naturally occurring TCRs bind self (tumor) peptides with low affinity and have a much higher affinity for foreign antigens. This complicates isolation of naturally occurring, high affinity TCRs that mediate more effective tumor rejection for therapeutic purposes. An attractive approach to resolve this issue is to engineer high affinity TCRs in vitro using phage, yeast or mammalian TCR display systems. A caveat of these systems is that they rely on a large library by random mutagenesis due to the lack of knowledge regarding the specific interactions between the TCR and pMHC. We have focused on the mammalian retroviral display system because it uniquely allows for direct comparison of TCR-pMHC-binding properties with T-cell activation outcomes. Through an alanine-scanning approach, we are able to quickly map the key amino acid residues directly involved in TCR-pMHC interactions thereby significantly reducing the library size. Using this method, we demonstrate that for a self-antigen-specific human TCR (R6C12) the key residues for pMHC binding are located in the CDR3β region. This information was used as a basis for designing an efficacious TCR CDR3α library that allowed for selection of TCRs with higher avidity than the wild-type as evaluated through binding and activation experiments. This is a direct approach to target specific TCR residues in TCR library design to efficiently engineer high avidity TCRs that may potentially be used to enhance adoptive immunotherapy treatments.