Biology Cheat Sheet

1. Detecting ‘self’ and ‘non self’ molecules: the role of antigens and the membrane receptors. Class I MHC molecules | Class II MHC molecules | Are found on almost all nucleated cells of the body (so are not on red blood cells) * Body Cells that have become infected or become cancerous can display antigens by using their Class I MHC molecules on their cell surface * These antigens that get displayed were made inside these cells * Cytotoxic T cells will recognise antigens displayed in this way and will destroy infected cell| * Are only found on certain cells (usually B cells, macrophages and dendritic cells) * These cells are generally known as antigen presenting cells (APCs) * These antigens presented in this case were taken in and degraded by these cells (by endocytosis or phagocytosis) * The foreign material is broken down, and antigens displayed on the cell surface via Class II MHC molecules * Helper T cells recognise antigens displayed in this way| The antigens, signal to other cells so they may either know what to look for or know to destroy the cells that these antigens are attached to. 2. Pathogens: AIDS/HIV Type | Caused by the Human Immunodeficiency Virus | Methods of control| Reverse transcriptase inhibitors: These drugs inhibit the ability of the virus to make copies of itselfProtease inhibitors (PIs): These medications interrupt virus replication at a later step in its life cycle, preventing cells from producing new viruses. Transmission| Through the exchange of body fluids, blood, semen, vaginal fluids, saliva (sexual transmission, blood products)| How it causes disease in the host| The HIV virus infects The cells disabling the normal immune process| Symptoms| pneumonia caused by Pneumocystis, which causes wheezing; brain infection with toxoplasmosis which can cause trouble thinking or symptoms that mimic a stroke; widespread infection with a bacteria called MAC (mycobacterium avium complex) which can cause fever and weight loss; yeast infection of the swallowing tube (esophagus) which causes pain with swallowing; widespread diseases with certain fungi like histoplasmosis, which can cause fever, cough, anemia, and other problems. | 3. Non- Specific Immune responses : Involves physical and chemical barriers, is not effected by any prior encounter with that agent, HAS NO “MEMORY” FOR FUTURE ENCOUNTERS Skin| Intact skin acts as a barrier against entry by pathogens, Glands in the skin secrete fatty acids and sweat contains salt, Acids create pH range that is unsuitable for the growth of harmful microbes, Most bacteria cannot tolerate the salty conditions of the skin surface. Natural Flora| Bacteria naturally live in body, inhabit the skin, the intestinal tract, These bacteria play a protective role against potentially harmful bacteria, Some members of natural flora opportunistic pathogens, sick injured rundown| Natural secretions | Tears and saliva contain enzymes that cause lysis of bacterial cells, Stomach acids kill harmful bacteria, Secretions also help flush away foreign particles| Mucous Membranes| Mucous secreted by the cells lining the respiratory tract help to trap bacteria, Cilia on these cells then sweep the foreign cells up to throat, swallow or cough it up, Mucous lining the digestive tract forms a protective barrier against penetration by microbes| Phagocytes| Type of white blood cell, Produced in the bone marrow, Engulf and destroy microbes and other foreign particles, name refers to ‘cells that eat’, includes macrophages and neutrophils| Natural Killer cells| Type of white blood cell, Kill virus-infected cells| Complement proteins | 20 different comp proteins, most made in liver, circulate blood stream, become active when infection occurs, help by 1) sticking to microbes to attract phagocytes 2) Coat bacteria so phagocytes ingest them easier, 3) some cause lysis of foreign cells| Interferon| Important group of immune proteins, Are secreted by virus infected cells, they can act on cells yet to be infected helping to make more resistant to infection, interferon acts quickly, antibodies take longer to work| Cytokines | These proteins act as messengers between cells, most cells produce cytokines, especially T cells, Allow different immune cells to communicate and between other body systems, a cell can only respond if appropriate receptor to that cytokine, there are suppressors for cytokines (form of protein)| Inflammation| Area becomes red, reaction to an infection, blood vessels dilate, increased blood flow to area, increased permeability of vessels, Phagocytes migrate to tissues from capillaries, Phagocytes release histamine (chemical) attracts more phago, Blood clots and pus form to seal the wound| Fever| Assists Defence, resets thermostat to higher temperature, helps production of T cells Inhibits the growth of bacteria and viruses , increases metabolic process and heart rate, more blood fast, white blood cells to infected regions| 4. Specific Immune Response

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B Cells (Lymphocytes)| Produced in the bone marrow, Mature in the bone marrow | T Cells (Lymphocytes)| Produced in the bone marrow, Matures in the Thymus (a small organ in your chest where they learn self from non self| Antigen | Any molecule that results in the production of an immune response involving antibodies, TIP ANTIbody GENerator, Antigens are usually proteins, but can include carbohydrates, An example of an antigen is a surface protein on a bacterial cell| Antibodies| Specialized proteins of the immune system, also called immunoglobulin’s (Ig), Y shaped, Secreted by B lymphocytes called plasma, They have a constant region, and a variable region| Antibody Specificity| Immunity involving antibodies circulating in body fluids is called “humoral immunity” Each antibody is specific for one antigen, The antigen binding site of the antibody molecule is complementary in shape for the antigen, Each arm of the molecule has an antigen binding site, The two antigen binding sites of an antibody are identical| Antibody Production| B cells are generated that differ in antigenic specificity (antigen they recognise) An individual B cell is ‘selected’ by an antigen, if an antigen molecule binds to the receptors on the lymphocyte, antigen selects the b cell that leads to its destruction, the selected B cell proliferates forming clones of teh cell that recognise the same antigen| Cell Mediated Immunity | Helper T cells = Th , Assist B cells to reproduce, form plasma cells which secrete antibodiesCytotoxic T Cells = TC , Kill infected body cells, secretes perforin, to rupture infected cells, only attacks the cells not the viral particlesSuppressor T cells = TS, Suppressors the immune response, acts as infection recedes stopping the response from continuing| Memory B and T Cells = response faster, longer and larger Similarities| Differences|

Both protect the body from invading pathogens | Non-specific immune response, targets anything and everything foreign or just fills in the space where a pathogen could effect| | Specific responses have a memory and are able to fight of the pathogen more easily the second time| | | 5. Similarities and the Differences 6. Identify examples of Acquired immunity | Active | Passive| Naturally | By surviving an infection, Memory cells were made and persist in the body. On further contact with the same antigen reaction will be faster, longer and larger| Via mothers placenta or breast feeding (no memory cells) immediate protection| Artificially | Injection of an inactive/weakened or altered/dead form of the micro organism or toxin (Vaccination)| Injection if the antibody serum.

Often produced in another organism or species. (no memory cells)| 7. Inappropriate immune responses Allergies| Autoimmune Disease| Allergen = an antigen that causes an allergic responseIgE antibodies produced in response to inital exposure to antigen bind to receptors, on second and third reactions get worse, this induces mast cell to release histamines | Auto = SelfInvolves failure to recognise self antigens on cells Response is to attach ‘non’ self with B and T cells, causing damage to own bodyE. g. Multiple Sclerosis ( myelin sheath on axon attackedDiabetes mellitus (beta cells of pancreas attacked)| 8. Compare and contrast immune responses in plants and animals | Animals| Plants|

Compare | Physical Barrier – Skin, Mucous membranesChemical Barrier – Natural flora, Natural secretions, Active Response – Phagocytes, NK cells, B cells, T cells | Physical barriers – Hairs, Thorns, spines, waxy cuticle, thick cell walls. Chemical Barriers – Compounds to inhibit pathogen growthActive Response – Encapsulate the affected tissue (gall) stopping the spread of the disease, secretion of antibiotic substance, release toxins to destroy pathogen, disrupting its metabolic processes| Contrast| Immune response consists of the whole body| There is no Circulatory system and so plants cannot quickly send specific cells to combat the pathogen|

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