Human immune system via multiple endogenous ligand–receptor pairs

The human immune system is a complex network of cells, tissues, and organs that work together to defend the body against foreign invaders and maintain homeostasis (Janeway's Immunobiology, 9th edition). This system operates through a vast array of endogenous ligand-receptor pairs, such as cytokines and their receptors, chemokines, and immune checkpoint molecules like PD-1/PD-L1 and CTLA-4/B7 (Nature Reviews Immunology, 2018). These interactions facilitate signal transduction, cell recruitment, and the regulation of immune activation or suppression. While these pathways are critical for health, their dysregulation is central to the pathogenesis of cancer, autoimmune disorders, and chronic inflammation. Because this entry refers to the entire immune system rather than a specific molecular entity, it is considered too broad to be classified as a single therapeutic target in drug development (NCBI Bookshelf, NBK279364).

Other names

Immune systemImmune signaling networkEndogenous ligand-receptor interactionsImmune checkpoint pathwaysCytokine-receptor network

Drugs targeting the immune system typically act by agonizing or antagonizing specific ligand-receptor interactions to either enhance immune surveillance (e.g., checkpoint inhibitors in oncology) or suppress pathological inflammation (e.g., cytokine antagonists in autoimmunity) (Nature Reviews Immunology, 2018).