Cytokines: Classification, Receptors, and Functions

Cytokines are small, low-molecular-weight regulatory proteins that coordinate immune and inflammatory responses by mediating communication among immune and non-immune cells. They are classified as pro-inflammatory, anti-inflammatory, or pleiotropic based on their biological functions. Cytokines act through specific cell-surface receptors, activating signaling pathways such as JAK/STAT, NF-κB, MAPK, PI3K/AKT, and SMAD to regulate gene expression, cell proliferation, differentiation, and survival. Dysregulated cytokine signaling contributes to the development of autoimmune, inflammatory, infectious, metabolic, cardiovascular, diabetic, and neurodegenerative diseases. Consequently, cytokines and their receptors serve as important biomarkers and therapeutic targets for numerous immune-mediated disorders.