Summary from mondays lesson- immunity so far!

1st line of defence:

Mechanical, biological, physical and chemical

 

examples below

 

Skin 

Dry; composed of dead cells containing keratin (protein) – keratin cannot be

digested easily – protective barrier to pathogens; outer layer of cells are   shed taking bacteria with them.  Microbes can only penetrate when surface is broken; shedding of skin

Sebum (sebaceous glands) contains long chain fatty acids – lowers pH (acidic- pH 5.4) – inhibits growth of microorganisms and viruses

Sweat (sweat glands) – contains lysozyme – digests cell wall of bacteria

Tears – lysozyme and washing action 

Gut

Saliva – lysozyme; amylase

HCL acid in stomach – destroys ingested bacteria

Mechanical flushing – due to movement of contents and fibre

Respiratory tract

Mucus (goblet cells) – traps particle and microorganisms

Cilia – sweeps mucus towards throat

Urinary/Reproductive tract

Semen (male) – spermine – antibacterial

Vagina – mucus membrane - acidic (lactic acid)

Urethra – acidic (due to acidic urine); washing action of urine

2nd line of defence:

•Pathogen recognised as foreign – pathogen is antigenic; chemotaxis

•Pathogen attached to phagocyte by antibody and surface receptors

•Engulfed by phagocyte by endocytosis – invagination of plasma cell membrane to form a phagosome (a membrane bound vesicle containing the pathogen)

•Lysosomes (containing lysins & hydrolytic enzymes) fuse to phagosome

•Release of H2O2, HCl, free radicals into phagosome

•Digest pathogen – harmless products removed (egested / excreted)  or used by phagocyte

•Phagocyte also displays antigenic components on external surface of plasma cell membrane (antigen presentation) to start immune response

3rd line of defence:

Immune Response

Body’s reaction to a foreign antigen or pathogen

Antigen

Substances capable of eliciting  the immune response (production of antibodies – which are usually proteins – termed immunoglobulins).  Any agent (foreign) to which an Ab can bind

Antibody

Immunoglobulin (proteins) produced in response to antigen during the immune response

Agglutinate (clump) pathogens (antigens) – for easier phagocytosis

Coat pathogen – to attract other chemicals (termed complement proteins), that destroy the pathogen