Leukotriene B4 is a lipid-derived inflammatory signaling hormone involved in leukocyte recruitment, immune-cell activation, chemotaxis, and inflammatory amplification. LTB4 functions as one of the most potent chemotactic mediators within the innate immune system, guiding neutrophils and additional leukocytes toward sites of tissue injury or microbial challenge.
The hormone promotes leukocyte adhesion, migration, degranulation, reactive oxygen species generation, and cytokine production. Through these actions, LTB4 strengthens inflammatory coordination and immune defense signaling. It also contributes to vascular permeability changes and communication between immune cells during acute inflammatory responses.
LTB4 is synthesized from arachidonic acid through the lipoxygenase pathway. Phospholipase A2 first releases arachidonic acid from membrane phospholipids. Five-lipoxygenase, together with five-lipoxygenase-activating protein, converts arachidonic acid into leukotriene A4 intermediates that are subsequently metabolized into leukotriene B4.
Production occurs mainly in neutrophils, macrophages, mast cells, eosinophils, and additional immune-cell populations. Because leukotrienes are synthesized on demand rather than stored, production reflects rapid immune activation and inflammatory signaling intensity.
LTB4 synthesis is regulated by inflammatory cytokines, immune receptor activation, oxidative stress, calcium signaling, phospholipase pathways, and cellular injury signals. Five-lipoxygenase activation is strongly dependent on intracellular calcium mobilization and membrane translocation processes.
LTB4 acts mainly through BLT receptors located on leukocytes and inflammatory cells. Activation of these receptors stimulates chemotaxis, adhesion molecule expression, cytokine signaling, and inflammatory amplification pathways. Enzymatic degradation pathways help limit excessive signaling and maintain tissue control. Through these integrated inflammatory lipid-signaling systems, LTB4 coordinates leukocyte recruitment, innate immune defense, inflammatory communication, and tissue response during acute immune activation.
LTB₄ is a leukocyte-derived signaling lipid that promotes neutrophil activation and migration during inflammation.
