IMMUNE SYSTEM- NON SPECIFIC AND SPECIFIC IMMUNITY, IMMUNE TOLERANCE
IMMUNITY: complex of physiological processes whose function is to store the constancy of the body’s internal environment by protecting the body from all foreign endogenous and exogenous factors
CATEGORIES OF IMMUNE SYSTEM
- Non specific immunity→ provides general protection
- 1st and 2nd lines of defence
- Specific Immunity→ body recognises specific pathogens
- 3rd line of defence
INNATE IMMUNITY
- Prevents entry of MOs into tissues or, once they have gained entry, eliminates them prior to occurrence of disease
- Its present from birth and is non-specific (Acts on multiple organisms w/ no specificity)
- Doesn’t become more efficient on subsequent exposure to the same organisms
- Disruption of mechanical barriers at body surfaces, skin and mucous membranes lead to infection
- Antibacterial substances in secretions (e.g. lysozyme, lactoferrin) lowers the pH of stomach contents
NON SPECIFIC IMMUNITY
FIRST LINE OF DEFENCE:
- Mechanical Barrier:
- Skin
- Mucosa
- Chemical Barrier:
- Saliva
- Enzymes
- Secretory immunity
SECOND LINE OF DEFENCE:
- Non specific inflammation
- Phagocytosis:
- Neutrophils
- Macrophages
- Histiocytes
- Natural Killer Cells
- Kill tumour cells
- Kill infected cells
NON-SPECIFIC PROTECTIVE FACTORS:
- TISSUE FACTORS:
- Skin
- Mucosa
- In the mouth- continuous oral mucosa
- HUMORAL FACTORS:
- mediators
- CELLULAR FACTORS:
- Act after overcoming tissue barrier
- Vascular cell phenomenon- inflammation
- Sensitized cells
- Haematopoietic- neoplastic cells
- Cells of specific immunity
Protective cells are macrophages and microphages (PMNs, 3 cell populations, mature cells- eosinophils, neutrophils, basophils, mast cells, platelets and killer cells)
MACROPHAGES:
- Mononuclear phagocytes derived from monocytes
- Includes: histiocytes, fixed macrophages (in lymph nodes and spleen), osteoclasts, Kuppfer cells, microglial cells, Langerhans Cells
- Macrophages have receptors for Immunoglobulins, complements, antigens and lymphokines
- They cause “oxidative burst” which releases a superoxide anion that turns into H₂O₂, kills the pathogenic factor and digests it intracellularly
- They then transfer antigens to lymphocytes and sensitises them to induce a specific immune response
- They separate bioactive substances and regulate the immune response
NEUTROPHILS:
- Involved in inflammation
- They separate membrane oxidases and include the object within the cell, forming phagosomes
EOSIONOPHILS:
- Regulates allergic reactions
- Includes: interleukins, interferons, cytokines, growth factors
BASOPHILS:
- Involved in anaphylactic degranulation which is mediated by IgE antibodies
- They posses receptor binding sites and act with exocytosis
MAST CELLS:
- Involved in non-specific inflammation, allergic reactions of immediate type and in degranulation
- They release histamine, serotonin, bradykinin and hyaluronic acid
PLATELETS:
- Nuclear free cytoplasmic fragments derived from bone marrow megakaryocytes
- They have haemostatic function and are involved in coagulation
KILLER CELLS:
- Located in circulating blood and represents a 1/3 of lymphocyte population