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Immunology - 3.2 - Coggle Diagram
Immunology - 3.2
NATURAL BARRIERS
- Pathogens need to enter an organism to cause disease
- Natural barriers in the body reduce the risk of infection
- Non - specific means they work in the same way regardless of the type of pathogen
Tears and saliva: - Contains an enzyme called a lysozyme
- Hydrolyses peptidoglycan in bacterial cell walls leading to cell lysis
Skin:
- Physical barrier
- Vitamin C is needed to make strong connective tissue
Natural Skin flora: - Outcompete pathogenic bacteria - Natural skin flora is not easily removed or washed off
Ciliated epithelial cells:
- Goblet cells secrete mucus which traps microorganisms in inhaled air
- Cilia waft mucus and trapped microorganisms up and out the trachea
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- The human body is a host because there are many organisms living in/on the human body
- Mutualistic/symbiotic relationship
- Two species that live together to their mutual advantage
Blood Clotting - Seals wounds and prevents entry of microbes
Inflammation - Increased blood flow to the area brings large numbers of phagocytes.
- Increased temperature decreases growth of microbes
Phagocytosis - Macrophages and neutrophils are white blood calls that engulf microbes and digest them
SPECIFIC IMMUNE RESPONSE
- Triggered by any non - self antigen
- Specific to the pathogen
Humoral Response:
- Response to antigens found outside of cells moving freely in the blood
- B-lymphocytes - have specialised receptors on their plasma membranes
- Production and secretion of antigen specific antibodies
- B lymphocytes, as well as phagocytic cells re made out of bone marrow and are matured in the spleen and lymph nodes
- When activated, cells can move out of the lymphatic system and travel to the site of infection
Clonal selection
- Each B lymphocyte has receptors for the detection of a specific antigen
- Macrophages engulf pathogens and after phagocytosis become antigen presenting cells. The macrophages then move to the lymph nodes and present the antigens to the B lymphocytes
- When the receptors on the B lymphocyte have a complementary shape to the antigen. That specific B lymphocyte is selected and activated
Clonal expansion and differentiation
- The specific B lymphocyte proliferates/ divides by repeated mitotic divisions to produce many B lymphocytes each with a specific receptor
- The B lymphocyte then differentiates into a:
- B - plasma cells secrete antibodies (with a specific shape complimentary to the antigen)
- B - memory cells which remain in circulation ready to divide if the same antigen is encountered again (in the future)
Cell mediated immune response:
- Response to antigens presented on the surface of cells
- Direct cell contact
- Destruction of pathogens, infected cells and cancerous cells
- T lymphocytes are made in the bone marrow and mature in the thymus
- T lymphocytes have specialised receptors on their plasma membranes
- Clonal selection can take place in the spleen, thymus or lymph nodes
- When the virus enters the host cell, viral antigens can end up being presented on the plasma membrane
- A specific t helper lymphocyte with receptors complementary to the shape of the viral antigen is selected
- Proliferation/repeated mitotic divisions of the specific t lymphocyte
- The t lymphocyte then differentiate into:
- T killer cells - which target specific cells and cause cell lysis/death
- T helper cells - which release cytokines
- Cytokines stimulate:
- B lymphocytes to initiate an antibody response
- Phagocytosis my macrophages
- Clonal expansion of B and T lymphocytes
- T memory cells - which remain dormant in circulation until the host is next exposed to the same antigen
Antibodies:
- Look at diagram in booklet
- Antibodies have variable sites that are complementary to the antigen
- An antigen antibody complex forms when the antibody binds to its specific antigen
- Agglutination - As there are two binding sites, two antigens can be joined by one antibody molecule
- When antigen - antibody complexes are form, pathogens are clumped together. Agglutination makes it easier for phagocytes to locate pathogens and engulf many of them at once
- Antibodies can form antigen - antibody complexes with toxin molecules
- The complex prevents the toxin from binding to receptors on host cells and damaging them. the toxin is neutralised
- When antibodies bind to pathogen antigens, they may block the receptors which are needed to bind to host cells
- This means the pathogen cannot bind to or invade the host cells
PHAGOCYTOSIS
- Macrophages and neutrophils engulf microbes by phagocytosis and present microbial antigens on their surface
- Pathogen binds/adheres to proteins on the surface of the phagocyte/macrophage
- Pseudopodia wrap around the pathogen and engulf it by endocytosis (requires ATP)
- A vesicle called a phagosome is formed
- The phagosome fuses with lysosomes which contain hydrolytic enzymes
- The pathogen is digested
- Debris is released from the cell by exocytosis (requires ATP)
- Antigen presentation. Antigens from the pathogen are presented on the cell membrane of the macrophage. The macrophage becomes an antigen presenting cell.
ANTIGENS
Antigen - A protein that is recognised as non - self and stimulates an immune response. - Each type of pathogen has its own antigens - Antigens are usually proteins but can be a glycoprotein of polysaccharide. Antigens are found on the surface of bacteria, toxins, viruses - Antigens have a specific shape
Antigen presentation - non - self antigens are presented to cells of the immune system to stimulate an immune response
INFLAMMATION
- When the skin is broken histamines are released
- Arterioles dilate bringing more macrophages and neutrophils to the area
- Gaps between the endothelial cells widen
- Platelets leave the arteriole and with protein clotting factors seal the wound
- Macrophages leave the arteriole and engulf microbes by phagocytosis
- Blood delivers heat to the area