Innate system and natural killer cells

Imunosni sustav razlikuje vlastito od stranog i odstranjuje potencijalno štetne strane molekule i stanice iz organizma. Imunosni sustav također ima sposobnost prepoznavanja i uništavanja promijenjenih vlastitih stanica koje potječu iz tkiva domaćina. Antigen je svaka molekula koju imunološki sustav prepoznaje. Urođeni (prirodni ili nespecifični) imunitet ne zahtjeva prethodni kontakt s antigenom za aktivaciju. Ukoliko virus ili bakterija prođu kožu ili sluznicu na našem tijelu i napadnu našu stanicu, aktiviraju se signali koje odmah registiraju prirodne stanice ubojice (NK stanice). One imaju sposobnost uništiti inficiranu stanicu u nekoliko sati dok zdravu poštede. Prirodne stanice ubojice pomažu i u obrani od tumora na način da, identificiraju i razlikuju tumorske stanice od normalnih. Sve zdrave stanice u tijelu sadrže MHC I receptore, a ukoliko je stanica zaražena ona neće posjedovati ove receptore. Ako NK stanice nemogu pronaći MHC I receptore na nekoj stanici odmah ju uništavaju.The immune system differentiates its own from the foreign and removes potentially harmful alien molecules and cells from the organism. The immune system also has the ability to recognize and destroy its own cells, those from the host tissue, but have been some ways transformed. An antigen is any molecule that is recognized by the immune system. Innate (natural or non-specific) immunity does not require prior contact with activating antigen. If a virus or bacterium passes the skin or mucous membrane in our body, and attacks our cells, the signals immediately register the natural cells of the killer. If the virus or bacteria pass through the skin or mucous membrane in our body and attack our cells, the signals that are activated are immediately registered by the natural killer cells (NK cells). They have the ability to destroy the infected cell in a matter of hours while not affecting the healthy cells. Natural killer cells also help in protecting against tumors by identifying and distinguishing tumor cells from normal. All healthy cells in the body contain MHC I receptors, and if the cell is infected it will not possess these receptors. If the NK cells can not find the MHC I receptors on a cell, they will immediately destroy them