The configuration of the immune system, immune mechanisms and functional disorders

Imunitet se definira kao otpornost na bolesti, posebno zarazne bolesti. Skup stanica, tkiva i molekula koje posreduju u otpornosti na infekcije naziva se imunosni sustav, a koordinirana reakcija tih stanica i molekula na zarazne mikrobe uključuje imunosni odgovor. Obrane domaćina grupirane su pod prirođeni imunitet koji pruža neposrednu zaštitu od invazije mikroorganizma te stečenog imuniteta, koji se razvija sporije i pruža specijaliziraniju obranu od infekcija. Prirođena imunost, koja se naziva i nespecifična imunost, uvijek je prisutna kod zdravih osoba te spremna da blokira ulazak mikroorganizma i brzo eliminira mikroorganizme koji uspiju ući u tkivo domaćina. Stečena imunost, također nazvana i specifična imunost, zahtijeva širenje i diferencijaciju limfocita kao odgovor na mikroorganizme prije nego što može pružiti učinkovitu obranu; odnosno prilagođava se prisutnosti mikrobnih napadača. Autoimunost se općenito definira kao pojava u kojoj protutijela ili T stanice reagiraju s autoantigenima, a autoimune bolesti nastaju kao posljedica poremećaja u smislu imunosti na vlastite antigene, a očituje se oštećenjem vlastitog tkiva. Prekomjerna imunoreakcija može izazvati štetni upalni odgovor te se radi o imunosnoj preosjetljivosti. Stanje alergije ili preosjetljivosti nastaje kada imunosni sustav reagira na bezopasne tvari u okolišu, poput hrane, peludi trava, kućne prašine ili dlake kućnih ljubimaca. Posljedica nedostatka ili odsutnosti elemenata imunosnog sustava, uključujući limfocite, fagocite i sustav komplemenata, naziva se imunodeficijencija. Virus humane imunodeficijencije (HIV) je virus koji inficira stanice imunosnog sustava, uglavnom CD4+ T limfocite te uzrokuje progresivno uništavanje tih stanica. Imunokomprimitirani pacijenti mogu zahtijevati dužu hospitalizaciju irehabilitaciju, stoga medicinska sestra ima bitnu ulogu u zdravstvenoj skrbi.Immunity is defined as resistance to diseases, especially infectious diseases. The set of cells, tissues and molecules that mediate resistance to infection is called the immune system, and the coordinated response of these cells and molecules to infectious microbes comprises the immune response. Host defenses are grouped under innate immunity, which provides immediate protection against invading microorganisms, and acquired immunity, which develops more slowly and provides a more specialized defense against infection. Innate immunity, which is also called non-specific immunity, is always present in healthy individuals and is ready to block the entry of microorganisms and quickly eliminate microorganisms that manage to enter the host's tissue. Acquired immunity, also called specific immunity, requires the proliferation and differentiation of lymphocytes in response to microorganisms before it can provide an effective defense; that is, it adapts to the presence of microbial invaders. Autoimmunity is generally defined as a phenomenon in which antibodies or T cells react with autoantigens, and autoimmune diseases arise as a result of disturbances in the sense of immunity to one's own antigens, manifested by damage to one's own tissue. An excessive immune reaction can cause a harmful inflammatory response, and this is immune hypersensitivity. An allergy or hypersensitivity condition occurs when the immune system reacts to harmless substances in the environment, such as food, grass pollen, house dust or pet dander. The consequence of the lack or absence of elements of the immune system, including lymphocytes, phagocytes and the complement system, is called immunodeficiency. The human immunodeficiency virus (HIV) is a virus that infects cells of the immune system, mainly CD4+ T lymphocytes, and causes the progressive destruction of these cells. Immunocompromised patients may require longer hospitalization and rehabilitation, therefore the nurse plays an important role in health care