Immunity:- Barriers to entry, Nonspecific, Specific & Secondary Infection

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Barriers to Entry

·         Earwax- Bacteriocidal

·         Mucus and Cilia- Prevent the entry of pathogens into lungs

·         Keratin in Skin- Waxy & imperiable to water and Pathogens

·         Blood clotting- Seals wounds

·         Lysozyme- in eyes, mouth and nose secretions break down the bacteria cell walls.

·         Vaginal secretions- acidic 

·         Acid in stomach- kills bacteria

·         Microbes - large numbers of harmless microbes that live on the skins surface reduce the colonization by other bacteria

·         Bacteria in intestines- Harmless bacteria competitively exclude pathogenic bacteria


Non Specific Immune Response

·         Lysozyme:- an enzyme in nasal secretions, tears and saliva that breaks down the bacteria cell wall.

·         Inflammation:- Mast cells and damaged white blood cells releasehistamine causing the arterioles to dilate. The capilleries become morepermiable which causes blood flow to the are to increase therefore causing Plasma fluid, white blood cells and antibodies to leak out into the tissue. This causes Oedema

·         Phagocytosis:- white blood cells engluf, digest and destroy bacteria andforeign material. The phagocytes include neutrophils and monocytes.

·         Interferon. Virus infected cells produce Interferion. The production of theis chemical prevents the viruses to multiply. Interferon limits viral protein synthesis


Specific Immune responses- Humoral- Activation of T helper Cells

·         Pathogen with antigens of surface is engulfed by macrophage

·         Macrophage presents antigens via MHC’s on its 


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