Inflammation occurs when pathogens infects various tissues in the body, inciting an immune response.
Mast cells are resident cells in many types of tissues and are rich in histamine and heparin. They release histamine rapidly into the interstitium, which triggers an immune response.
Histamine acts on the capillaries near the infected tissue by dilating them to allow for more blood flow and increasing their permeability to immune cells.
Macrophages can travel through the more permeable capillary wall to the interstitium and engulf any pathogens through phagocytic activity.
Macrophages also signal other immune cells by releasing cytokines. Cytokines help initiate a cascade of intracellular signaling. There are numerous cytokines, and these are responsible for different inflammatory and immune responses in the body by signaling to various immune cells.
Neutrophils respond to the cytokine stimulus and also extravasate through the capillary wall into the interstitium. Neutrophils are also phagocytes i.e. they consume and destroy pathogens intracellularly.
The last part of the immune response is the adaptive immune response. B- and T-cells from the humoral and cell-mediated responses arrive later at the site of tissue injury/inflammation to produce antibodies (B-cells), destroy infected cells (killer T-cells), and create memory cells (B-cells) in case of future reinfection.
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