CD74 deficiency impairs Treg accumulation and function in the tumor

Regulatory T cells (Tregs) are known to actively adapt to the microenvironment in which they reside. However, how Tregs are reshaped in the tumor tissue remains under defined. We observed that in human tumors, Tregs selectively overexpress at the surface CD74, the MHC class II-associated invariant chain. Beyond its role in antigen presentation, CD74 has been described to impact gene transcription and cell migration, however, its role in Treg biology remains unknown. Here, we found that CD74KO Tregs exhibited major defects in the organization of their actin cytoskeleton and intracellular organelles and, consistently, they failed to accumulate in tumors and to suppress the anti-tumoral T-cell response. Strikingly, this phenotype did not result from a generic defect of CD74-deficient Tregs as their phenotype, proliferation, and suppressive function in vitro and in vivo during Graft-versus-Host disease were not affected. Our results reveal a new role for CD74 in Tregs and uncover CD74 potential as novel target to interfere with Treg anti-tumor activity. Overall design: Regulatory T cells isolated from healthy-donor blood are expanded for bulk-RNA sequencing analysis