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.
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