Immunity Immunity Immunity is the capability of multicellular

Immunity

Immunity • Immunity is the capability of multicellular organisms to resist harmful microorganisms from entering their cells. Immunity involves both specific and nonspecific components. The nonspecific components act as barriers or eliminators of a wide range of pathogens irrespective of their antigenic make-up.

Immune response A specific defence function of the body that protects the tissues against invading pathogens, foreign materials and malignancies. It consists of : • Cell mediated immune response, and • Humoral immune response.

Resistance to infection The body has two main lines of resistance to infection – • Non-specific defences, and • Specific immune response.

Can be External – 1 st line of defence. • Mechanical & chemical barriers that protect the potential invasion points for invasion by micro-organisms. Non-specific defences Internal – 2 nd & 3 rd line of defence. • Inflammatory process • Phagocytic cells • Natural killer cells, and • Protective proteins.

External Defences Physical barriers – • Skin • Mucus membranes • Normal body flora • Some body secretions

Skin • The body as a whole is protected by skin – an intact waterproof membrane against micro-organisms. • Sweat and sebum secreted through the skin are also bactericidal to some organisms.

• The respiratory tract is lined by mucus membrane. • Mucus is sticky and catches micro-organisms and dust particles in it. Mucus membranes • Phagocytes consume dangerous bugs, and the airway is lined by cilia that waft inhaled matter away from the lungs into the oropharynx for expectorating or swallowing

• The gastro-intestinal tract is lined by mucus membrane and the normal flora of the bowel. Mucus membranes • Saliva produced by glands in the mouth produce the enzyme lysozyme, which inhibits the growth of bacteria. • Acids in the stomach have a low p. H which is unfavourable to most pathogens. • Bile in the duodenum has a high p. H, which is also bactericidal.

• Lysozyme, also known as muramidase or Nacetylmuramide glycanhydrolase, are a family of enzymes (EC 3. 2. 1. 17) which damage bacterial cell walls by catalysing hydrolysis. Lysozyme definition • Lysozyme is abundant in a number of secretions, such as tears, saliva, human milk and mucus. It is also present in cytoplasmic granules of the polymorphonuclear neutrophils (PMN). • Large amounts of lysozyme can be found in egg white.

Other mechanical methods • The urinary tract is protected by the flushing action of urine as it flows from the bladder, and urine is acidic, which is not conducive to bacterial growth. • The vagina is protected by normal flora called lactobacilli, and the p. H is low to inhibit invasion by other organisms.

• Skin Examples of first line body defence mechanisms • Mucus membrane • Mucus • Chemicals • Epiglottis • Tonsils • Lacrimal glands • Urinary tract • Vaginal secretions

Internal defences are the automatic protective functions of the – Internal Defences • Inflammatory process • Phagocytic cells • Natural killer cells, and • Protective proteins.

Inflammation Organisms that manage to get through the body’s skin or past the mucus membrane trigger an internal inflammatory response – this is the body’s attempt to destroy as many invading organisms as possible, and confine them to the point of entry. It is characterised by 4 basic symptoms: • Redness • Pain • Heat, and • Swelling.

• Phagocytes are white blood cells which are attracted to a site of infection by chemicals released from damaged cells. • They attack pathogens by engulfing and then digesting them. Phagocytic cells • Dead phagocytes become a thick yellowish substance called pus

Phagocytes in action

Natural killer cells • A specialised type of lymphocyte capable of binding to and killing pathogens by breaking holes in cell membranes and releasing destructive enzymes. • Particularly effective against parasites, some virus-infected cells, and some malignant tumour cells. • Made in bone marrow & the spleen.

Consist of : Protective proteins Complement proteins- Complement proteins help phagocytes identify pathogens. Interferons-Interferons are a group of proteins that are secreted by viral-infected cells. They bind onto surrounding cells and protect them from viral replication.

• A specific antibody has been produced to defend the body against a specific pathogen or the toxin it produces. Specific defences • An antigen is the term used for any foreign material including bacteria, viruses or toxins, that stimulates an immune response in the body. • Anti-bodies are proteins synthesised by the host that inactivate antigens.

im·mune (-myon) adj. 1. Of, relating to, or having resistance to infection by a specific pathogen. Immunity 2. Relating to the mechanism of sensitization in which the reactivity is so altered by previous contact with an antigen that the responsive tissues respond quickly upon subsequent contact.

Two types of lymphocytes involved in specific immunity T cells, and B cells. Lymphocytes They reside in areas of lymph tissue around the body, and circulate in the blood. They both attack antigens. T- cells are involved in cell-mediated immunity. B – cells are involved in humoral immunity.

Cell mediated immune response Two types of T – cells are involved in cellmediated immunity – T-helper cells Cytotoxic T cells. Particularly effective against fungi, parasites, malignant cells, and foreign tissue – e. g. Transplanted organs.

Humoral immune response • Noun 1. humoral immune response - an immune response (chiefly against bacterial invasion) that is mediated by B cells immune reaction, immune response, immunologic response - a bodily defence reaction that recognizes an invading substance (an antigen: such as a virus or fungus or bacteria or transplanted organ) and produces antibodies specific against that antigen

Can be: Immunity Innate Naturally acquired Artificially acquired

Genetically or inborn immunity – also known as non-specific immunity. • Inflammation Innate immunity • Complement system • Leukocytes • Phagocytes • Mast cells • Macrophages

• Passive natural immunity is acquired in-utero when immunoglobulins from the mother’s blood are transferred across the placenta and enter the foetal blood stream. Naturally Acquired Immunity • Also, post delivery, immunoglobulin is abundant in colostrum. • This kind of immunity is not long lasting. It may provide immunity only for a few months. • Active natural immunity is acquired when an individual is exposed to the disease and utilises the specific defences mechanisms of cellmediated anti-body mediated immunity. • Memory cells are created which will provide a swift response to any further exposure to that specific pathogen.

Artificially acquired immunity. Passive artificially acquired immunity is acquired by a direct injection of antibodies, or immunoglobulin. E. g. a nurse potentially exposed to Hep B via a needle stick injury can be given Hep B immunoglobulin in an attempt to provide instant protection from that virus.

Passive artificially acquired immunity Immunoglobulin - examples Antibodies – examples Rubella Anti venoms – snakes, spiders, box jelly fish, stone fish. Hepatitis A Botulism Hepatitis B Diphtheria Rabies Tetanus

Active artificially acquired immunity occurs via vaccines. Artificially acquired immunity Vaccines are suspensions of live, dead or attenuated (weakened) pathogens introduced into the body to stimulate the production of specific immunoglobulins. Specific vaccines provide protection for months to years. Examples: Measles Cholera Mumps Diphtheria Rubella Whooping cough Hepatitis Influenza BCG Polio

Immunity Summary

Reference • Australian Guidelines for the Prevention and Control of Infection in Healthcare (2010) | National Health and Medical Research Council. (2013). Nhmrc. gov. au. Retrieved 10 April 2016, from http: //www. nhmrc. gov. au/book/htmlaustralian-guidelines-prevention-and-controlinfection-healthcare-2010 • Koutoukidis, G, Stainton, K, Hughson, J & Tabbner, A (2013), Tabbner's nursing care, Chatswood, NSW, Churchill Livingstone. (Chapter 20: Infection prevention and control).

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