Innate immunity

Its a non specific immunity. 

It’s not long lasting defense system like adaptive immunity, but provides immediate defense against infection.

First line of defense against foreign organisms

Cells involved in innate immunity are  mast cells, phagocytic cells like macrophages, neutrophiles, dendritic cells, basophiles and eosinophiles, natural killer cells, γδ T cells.

Barriers which prevent the entry or growth of microorganisms inside the body: Skin, Phagocytic cells, Antibacterial proteins such as α defensin, Psoriasin.

Psoriasin is a small protein with potent antibacterial activity against E.Coli.

Anatomical barriers are skin which defense against the microorganism through the sweat, desquamation, flushing and organic acids. GI tract, which has defensin, gut flora, thiocynate, bile acids, gastric juice, and peristalsis. Airway and lungs has surfactant, mucociliary elevator. Eyes have tears. Nasopharynx has mucus, saliva, lysozyme.

C- Reactive protein belongs to family of pentameric proteins called pentraxins, which bind ligands in a calcium dependent reaction.

BPI (bactericidal/permeability-increasing protein) is 55 kDa proteins that bind with high affinity to LPS in the walls of gram negative bacteria and cause damage to the bacterium’s inner membrane.

iNOS (inducible nitric oxide synthetase), an enzyme that oxidizes L- arginine to yield L- citrulline and Nitric oxide (NO).

ROS species production

Oxygen O2 à .O₂^- à H₂O₂ à HClO^-

Oxygen is converted to superoxide anion by NADPH phagosome oxidase, and then Superoxide anion is converted to hydrogen peroxide by superoxide dismutase. Then with addition of chlorine ion, hydrogen peroxide is converted to hypochlorite by myeloperoxidase.

Natural killer cells produce interferon gamma and TNF alpha. These cytokines stimulate the maturation of dendritic cells. INFG is a mediator of macrophage activation and regulator of T helper cells development.