Quantitative Temporal in vivo Proteomics (QTiPs) deciphers the transition of inflammatory CD11b+,Ly6G-,Ly6Chigh myeloid cells into M2-like macrophages

Phenotypic transition of myeloid cells into distinct lineages in vivo is important in pathogen response. To monitor immune cell phenotype transitions in vivo, we developed a quantitative temporal in vivo proteomics (QTiPs) platform, performing multiplexed (10-plex) tandem-mass-tag (TMT)-based mass spectrometry on sorted cells collected from their in situ microenvironment during infection. We temporally characterized a poorly understood, virus-driven CD11b+,Ly6G-,Ly6Chigh-low myeloid cell population throughout an acute phase of infection in both the site of infection and bone marrow. QTiPs, in combination with phenotypic, functional and metabolic analyses, elucidated a pivotal role for inflammatory CD11b+,Ly6G-,Ly6Chigh-low cells in anti-viral immune response and viral clearance. Most importantly, the highly time-resolved QTiPs dataset showed the transition of CD11b+,Ly6G-,Ly6Chigh-low cells into M2-like macrophages which displayed increased antigen presentation capacities and bioenergetic demands late in infection. Our QTiPs approach precisely captures myeloid cell-macrophage transition in this population, and it is a novel platform for measuring temporospatial proteome transitions in vivo.