Alternative activation of mast cells by CD4+ T helper cells

Effector CD4+ T lymphocytes (Teff) infiltrate sites of inflammation and orchestrate the immune response by instructing local leukocytes. Mast cells (MCs) are tissue sentinel cells strategically located near blood vessels and T cell rich areas. MC/Teff cells interactions shape Teff cell responses but in turn, Teff cell action on MC is still poorly understood. Here, we analyzed the human MC/Teff cells interplay through the application of RNAseq and functional assays and showed that activated Teff cells induced a specific transcriptomic program in MCs driving them toward an inflammatory phenotype. Teff cells affected key MC immune functions as they induced prostaglandin, inflammatory cytokines and chemokines production and fostered FceRI-dependent degranulation. Moreover, Teff cell induced in MCs the capacity to regulate T cell responses through a wide-range of dedicated soluble and membrane ligands. Cell-Cell communication inference based on transcriptomic data indicated that IFN-g, IL-21, IL-27 and IL-1b were the main driver of MC differentiation program.