Arpad Szoor

This study sought to compare the behavior of Treg subsets displaying different coexpression patterns of Neuropilin‐1 (Nrp1) and Helios, under the influence of gut stress unrelated to hematopoietic stem cell transplantation, pretransplantation conditioning, and posttransplant gastrointestinal acute graft versus host disease (GI‐aGvHD). Host CD4 + /CD25 hi /Foxp3 + Treg cells, identified by flow cytometry, were isolated from various tissues of mice affected by these stressors. Expression of CD25, CTLA‐4, CD39, OX40, integrin‐β7, LAG3, TGFβ/LAP, granzyme‐A, ‐B, and interleukin‐10 was compared in four Treg subsets displaying Helios or Nrp1 only, both or none. Fluorescence‐activated cell sorter–sorted Treg subsets, displaying markers affected in a conditioning‐ and GI‐aGVHD‐restricted manner, were further investigated by transcriptome profiling and T‐cell suppression assays. We found that conditioning by irradiation greatly diminished the relative frequency of Helios + /Nrp1 + Treg, shifting the balance toward Helios − /Nrp1 − Treg in the host. Upregulation of integrin‐β7 and OX40 occurred in GI‐aGvHD‐dependent manner in Helios + /Nrp1 + cells but not in Helios − /Nrp1 − Treg. Sorted Treg subsets, confirmed to overexpress Nrp1, Helios, OX40, or integrin‐β7, displayed superior immunosuppressive activity and enrichment in activation‐related messenger RNA transcripts. Our data suggest that conditioning‐induced shrinkage of the Nrp1 + /Helios + Treg subset may contribute to the development of GI‐GvHD by impairing gut homing and decreasing the efficiency of Treg‐mediated immunosuppression.

Chimeric antigen receptor (CAR)-modified T cells brought a paradigm shift in the treatment of chemotherapy-resistant lymphomas. Conversely, clinical experience with CAR T cells targeting solid tumors has been disheartening, indicating the necessity of their molecular-level optimization. While incorporating CD28 or 41BB costimulatory domains into CARs in addition to the CD3z signaling domain improved the long-term efficacy of T cell products, their influence on early tumor engagement has yet to be elucidated. We studied the antigen-independent self-association and membrane diffusion kinetics of first- (.z), second- (CD28.z, 41BB.z), and third- (CD28.41BB.z) generation HER2-specific CARs in the resting T cell membrane using super-resolution AiryScan microscopy and fluorescence correlation spectroscopy, in correlation with RoseTTAFold-based structure prediction and assessment of oligomerization in native Western blot. While .z and CD28.z CARs formed large, high-density submicron clusters of dimers, 41BB-containing CARs formed higher oligomers that assembled into smaller but more numerous membrane clusters. The first-, second-, and third-generation CARs showed progressively increasing lateral diffusion as the distance of their CD3z domain from the membrane plane increased. Confocal microscopy analysis of immunological synapses showed that both small clusters of highly mobile CD28.41BB.z and large clusters of less mobile .z CAR induced more efficient CD3ζ and pLck phosphorylation than CD28.z or 41BB.z CARs of intermediate mobility. However, electric cell-substrate impedance sensing revealed that the CD28.41BB.z CAR performs worst in sequential short-term elimination of adherent tumor cells, while the .z CAR is superior to all others. We conclude that the molecular structure, membrane organization, and mobility of CARs are critical design parameters that can predict the development of an effective immune synapse. Therefore, they need to be taken into account alongside the long-term biological effects of costimulatory domains to achieve an optimal therapeutic effect.