IMMUNITY.pptx ppt in immunity it's simplified

Immunity

1. IMMUNITY DEF: Immunity refers to the resistance exhibited by the host towards an injury caused by microorganisms and their products. TYPES: Innate and Acquired A. INNATE OR NATIVE IMMUNITY It is the resistance that an individual possesses by birth, that is by virtue of his genetic and constitutional makeup. Innate immunity considered at the levels of, Species Immunity – Resistance towards a particular pathogen, shown by all members of a given species. Eg . Human beings are resistant to plant pathogens. Humans only can get infected with tetanus but not birds. Racial Immunity - Within a sps , different races may exhibit differences in susceptibility or resistance to infections. Eg . 1. African origin Negroes in USA are more susceptible to TB than Caucasians. 2. Races with sickle cell anaemia in the Mediterranean coast are highly resistant to Plasmodium falciparum infection. 3. Individual Immunity – The resistance to an infection varies with different individuals of the same sps . and race.

2. MECHANISM OF INNATE IMMUNITY EPITHELIAL SURFACES - SKIN Skin not only acts as mechanical barrier ,but also provide antibacterial secretions . Sebaceous secretions of skin contain unsaturated fatty acids (oleic acid) and free saturated fatty acids that have bactericidal and fungicidal actions. The relatively dry skin with high salt concentration in drying sweat are inhibitory or lethal to many mo’s . The normal flora of the skin help to prevent colonisation by pathogen. RESPIRATORY TRACT – Ciliary epithelia and mucosa of the RT has several innate defence mechanism. The very architecture of nose prevents entry of mo’s to a large extent, the inhaled particles being arrested at the nasal orifices. Those that pass beyond are held by the sticky mucus lining , and are swept back to pharynx by cilia, where they tend to be swallowed or coughed out. (coughing reflux). Those that manage to reach the pulmonary alveoli are ingested by the phagocytic cells present over there.

3. MOUTH AND INTESTINAL TRACT The mouth is constantly bathed in saliva which has inhibitory effect on many mo’s . Particles deposited in the mouth are swallowed and subjected to the action of the digestive juices. The high acidic pH of gastric juice destroys most mo’s . The normal flora of intestine further exert a protective effect by preventing colonisation of pathogenic bacteria. CONJUCTIVA The conjunctiva is freed of foreign particles by flushing action of lachrymal secretions and tears. Tears contain antibacterial substance called lysozyme that has bactericidal action on many mo’s . GENITOURINARY TRACT The flushing action of urine eliminate bacteria from urethra. Spermine in the semen have antibacterial activity. The acidic pH of adult female genital tract makes it inhospitable to many pathogens.

4. ANTIBACTERIAL SUBSTANCES There are many non-specific antibacterial substances present in the blood and tissues viz , Betalysin Basic polypeptides ( leukin from leucocytes, plakind from platelets) Lactoperoxidase in milk Interferons. Apart from these the complement system possesses bactericidal activity and plays an important role in the destruction of pathogenic bacteria. III. CELLULAR FACTORS – Once the infective agent has crossed the barrier of epithelial surfaces, the tissue factors come into play for defence. When an infective agent invades tissue an exudative inflammatory reaction occurs by accumulation of phagocytes at the site of infection. Phagocytic cells reach the site of inflammation in large number attracted by chemotactic substances and ingest bacteria. Phagocytic cells are of two types- Microphages (polymorphonuclear leucocytes) and Macrophages (mononuclear - hystocytes and reticuloendothelial cells.)

5. ACUTE PHASE PROTEINS : Infection or injury leads to a sudden increase in plasma concentration of certain proteins. C reactive protein(CRP) and some other acute phase proteins activate complement pathway and enhance host resistance , prevent tissue injury and promote repair of inflammatory lesions. TOLL-LIKE RECEPTORS: There are 13 different TLRs that recognise unique molecule patterns on microbes and enhance phagocytosis that lead to inflammatory reaction.

6. C. COMBINED IMMUNITY Sometimes a combination of active and passive methods of immunisation is employed . Passive immunity provides immediate (instant) protection till the active immunity becomes effective in a recipient host. ------------------------------------------------------- ASSIGNMENT : L ocal immunity H erd immunity Adjuvants