The CD28-transmembrane domain mediates chimeric antigen receptor heterodimerization with CD28

Abstract

Abstract Anti-CD19 chimeric antigen receptor (CD19-CAR)-engineered T cells are approved therapeutics for malignancies. The impact of the hinge (HD) and transmembrane (TMD) domains between the extracellular antigen-targeting and the intracellular signaling modalities of CARs has not been systemically studied. Here, a series of CD19-CARs differing only by their HD (CD8/CD28/IgG 4 ) and TMD (CD8/CD28) was generated. CARs containing a CD28-TMD, but not a CD8-TMD, formed heterodimers with the endogenous CD28 in human T cells, as shown by co-immunoprecipitation and CAR-dependent proliferation to anti-CD28 stimulation. This dimerization depended on polar amino-acids in the CD28-TMD. CD28-CAR heterodimerization was more efficient in CARs containing a CD8-HD or CD28-HD as compared to an IgG 4 -HD. CD28-CAR heterodimers did not respond to CD80 and CD86 stimulation but led to a significant reduction of CD28 cell-surface expression. These data unveil a new property of the CD28-TMD and suggest that TMDs can modulate CAR T-cell activities by engaging endogenous partners. Abstract Figure