Plasma membrane proteomes of differentially matured dendritic cells identified by LC MS/MS combined with iTRAQ labelling.

Dendritic cells (DCs) play a pivotal role in polarising Th lymphocyte subsets but it is unclear whatmolecular events occur when DCs generate Th2-type responses. Here, we analysed plasma membrane-enriched fractions from immature, pro-Th1 and pro-Th2 DCs and used a combination of iTRAQ labelling and LC?MS/MS to quantify changes in the proteomes. Analysis was performed on triplicate biological samples and changes verified by flow cytometry. MHC class II molecules and CD29 were up-regulated in pro-Th1 DCs whilst CD18 and CD44 were upregulated in pro-Th2 DCs. One of the most down-regulated molecules in pro-Th1 DCs was YM-1 whilst the greatest decrease in pro-Th2 DCs was NAP-22. Other molecules upregulated in pro-Th2 DC compared to pro-Th1 DCs included some potentially involved in protein folding during antigen processing (clathrin and Rab-7), whilst other non-membrane proteins such as enzymes/transporters related to cell metabolism(malate dehydrogenase, pyruvate kinase, and ATPase Na+/K+) were also recorded. This suggests that pro-Th2 DCs are more metabolically active while pro-Th1 DCs have a mature ?end state?. Overall, althoughseveralmolecules were preferentially expressed on pro-Th2 DCs, our proteomics data support the view of a ?limited maturation? of pro-Th2 DCs compared to pro-Th1 DCs