abstract
- Immune cells respond to a vast variety of stimuli to maintain a well-functioning immune system. Physiologic and innocuous or foreign and dangerous signals are recognized by cell surface receptors and initiate a signaling process, leading to cell responses including changes in shape, motility, growth, activation, differentiation, or production of effector molecules. Distinct cascades of interacting proteins and molecular messengers connect the recognized stimuli and relay information into the cytosol and/or nucleus to initiate effector functions either directly or through the initiation of gene transcription. Signaling pathways can be categorized based on the mechanisms by which environmental stimuli are sensed, such as cell surface receptor-mediated interactions or intra-cellular detection of lipid-soluble molecules. Receptor-mediated signaling can be further classified based on the presence or absence of enzymatic activity. This chapter focuses on fundamental concepts of cell signaling based on these groups of receptors and their intra-cellular signaling pathways. © 2025 Elsevier Inc. All rights reserved.