New in Version 41 is the topic Cellular responses to stress, including Regulation of Hypoxia-inducible Factor by oxygen. Topics with new or revised events include Immune System (MHC Class II mediated antigen processing & presentation), Metabolism (Abacavir transport and metabolism, Glycerophospholipid biosynthesis, Glycosaminoglycan metabolism, Linoleic acid and alpha-linolenic acid metabolism, O2/CO2 exchange in erythrocytes, PI Metabolism, Reversible hydration of carbon dioxide, and Activation of arylsufatases), Signal transduction (Signaling by TGF-beta Receptor Complex and Gastrin-CREB signalling pathway via PKC and MAPK), Extracellular matrix organization (Collagen biosynthesis and modifying enzymes) and Gene expression. New Disease pathways include Abnormal metabolism in phenylketonuria, Latent infection of H. sapiens with Mycobacterium tuberculosis, and Signaling by FGFR in disease. R Stephan and S Tripathi are our external authors. EG Canty-Laird, S Ezzat, T Huang, J Neefjes, K Rantanen, F Rauscher, M Wakelam are our external reviewers. Based upon feedback from our users, Reactome has started to provide Pathway Illustrations. New ones for this release are: Signaling by EGFR, Hemostasis, Respiratory Electron Transport System, RAF/MAP kinase cascade, Signaling by NGF, PIP3 activates AKT signaling, Signaling by FGFR, Signaling by Insulin receptor, Signaling by BMP, Signaling by TGF beta, Signaling by Notch, Pre-NOTCH Expression and Processing, Signaling by NOTCH1, NOTCH2, NOTCH3, and NOTCH4, Signaling by PDGF, Integrin cell surface interactions, Signaling by ERBB2 and ERBB4. For the systems biology community, we now offer SBGN export for all pathways. Our SBGN is generated using libSBGN Milestone 2. Protein pages in Reactome now include link outs to GeneCards annotations. An updated Reactome tutorial has been published in Current Protocols in Bioinformatics.