What is innate immunity or Natural Immunity?
Innate Immunity
Innate immunity is also known as native immunity. It is the resistance to an infection that an individual possesses by birth from parents.
It passes from one generation to another through genes.
For example; immune system recognized when certain invaders are foreign and dangerous. Such as; skin act as barrier to block germs from entering body.
Innate Immunity includes;
1. Species resistance
2. Racial immunity
3. Individual Immunity
1. Species resistance
Resistance to infection varies with the species of animals or human beings.
Metabolic, physiological and anatomical difference between species affect the ability of pathogen to cause infection.
For example; B. Anthracis infect only human not chicken.
S. typhi produces typhoid fever in man where as mice is resistant.
2. Racial Immunity
In human, racial resistance is explained on the basis of selectivity and servival in most cases. With one species, difference races show difference in resistance or susceptibility to infection.
For example; Algerian sheep is highly resistant to anthrax.
For example; Negros are higher resistance to malaria and yellow fever.
3. Individual Immunity
Some people appears to experience fever or less severe infection than other, even through they have same racial background and opportunity for exposure.
Different individual of the same species and races show variation in resistance to infection.
Such individual resistance is due to the combination of both innate immunity and adaptive (active) resistance factor such as:
Immunodeficiency
Age; child, young, old, women's age
Gender
Individual physical relation
Nutrition
Personal hygiene
Harmonal influence; Such as harmonal disorder; endocrine influence
Mechanism of Innate Immunity
In every individuals,
There are two types of resistance mechanism;
1. Non- specific immunity
2. Specific immunity
1. Non - specific immunity
It is common mechanism used against most types of infection and is found in all human beings. It involves;
1. Internal defence mechanism
2. External defence mechanism
1. Internal defence mechanism
Epithelial surface
Conjuctiva
Nose, nasopharynx and respiratory tract (mucus)
Mouth (saliva), stomach and intestinal tract
Genitourinary track (semen)
2. External defence mechanism
(Tissue factor)
a. Cellular factor
b. Humoral factor (realting to body fluids immune response)
a. Cellular factor (infective agent;infect tissue)
It includes;
1. Natural killer cell
2. Phagocytosis
3. Inflammation
4. Pyrexia (Fever)
1. Phagocytosis
Phagocytosis is a cellular process by which foreign particle or infectious agents are ingested and digested by phagocytic cells.
The major lysoenzymes through which phagocytic cell kill microorganism include;
Lysoenzymes are; Lysozyme, Hyaluronidase, Collagenases, Lipases, Ribonuclease, Elastases
Process of Phagocytosis
The process of phagocytosis requires a preliminary attach of the microbes to the phagocytic cell surface.
The process of phagocytosis consist 4 stages;
Stages are;
1. Chemotaxis
Phagocytes reach site of infection, bring attracted by chemotactic substances produced at the site of infection.
2. Attachment
Infective agent gets attached or adhered to membrane of phagocyte.
3. Ingestion
Phagocytes engulf the infective agent/ material into a vacoule (phagosome), the membrane of which fuses with a lysosome in cytoplasm forming phagolysosome.
Lysosome contains hydrolytic enzymes and other bactericidal substance.
4. Intracellular Digestion
Intracellular digestion of engulfed microbes takes place few minutes of phagocytosis by action of hydrolytic enzyme.
The bacterial component are degarded in several hours.
Phagocytic Cell
1. Microphages
Polymorphonuclear leucocytes called polymorphs (neutrophils) contains numerous enzyme and antibacterial substance for killing and degradation of bacteria.
2. Macrophages
These are mononuclear phagocytic cells include; Monocytes.
Present in kuffer cells (in liver), spleen, lymph nodes, thymus.
When macrophages ingest a microorganisms, the phagocytic cell increases it oxygen consumption term as "respirator brust".
2. Natural killer cells
(NK cells, K cells, Killer cells)
NK play major role to kill directly tumor cells and virally infected cell without ingesting them.
2. Inflammation
Inflammation is non specific mechanism of defence with characteristic signs of redness, swelling, heat, pain and altered function.
According to this inflammatory response, the microorganism like bacteria, virus etc enter in the body tissue through some injury - the microbes produce some toxic substances which kill tissue or cell.
The damaged cell release histamine which causes inflammation.
Infected area become red, warm and swollen and increase permeability of capillary wall.
The phagocytes show chemotactic response and are attracted by chemicals released from Inflammation area.
The phagocytes move towards infected or injured area engulf the invading microbes.
The dead microb and white blood corpsules from the pus in wound region.
Types of inflammatory response
1. Localized Inflammation
When inflammatory response occurs only in injured or infected are called localized Inflammation.
2. Systemic inflammation
When inflammatory response occurs throughout the body, called systemic inflammation.
Increased WBC, resulting fever or pyrexia.
3. Pyrexia (fever)
Stimulates the phagocytic activity and inhibits the growth of microorganisms.
The fever decreases the iron level in the body (because iron promotes growth of bacteria).
Fever also increases the production of interferon.
2. Humoral factor
1. Complement
2. Interferons
3. Bactericidin; kill bacteria
4. Lysozyme
Bactericidal enzyme found in tears, nasal/ intestinal secretion and other body fluids.
5. Beta-lysin
Able to kill some Gram +ve bacteria.
6. Properdin
Lysis of gram -ve bacteria and inactivates some Viruses.
7. Basic polypeptides
Bactericidal substances acting upon cell wall of bacteria.
1. Complement
Complement is a heat labile substance present in serum and tissue fluid of all normal individuals.
It enhances phagocytosis and kill most of G-ve bacteria.
2. Interferon
Interferon is a natural antiviral substance which inhibits intracellular viral replication.
It's primary role is against viral infection.
2. Specific immunity
(Specific resistance)
The Immunity against a particular organisms known as specific immunity.
For example; People having CRR 5 recessive gene are resistant for HIV infection.
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