WBCs and Resistance to disease

Frage	Antworten
Non-specific	Non-specific – inborn (‘innate’), general , fast Works against any type of invading agent
Specific	Acquired following exposure to specific pathogen; slower response.
2 Main categories of WBCs	Granulocytes & agranulocytes
Neutrophils	Most commont - 50-70% of total Phagocytic 1st on scene at infected site Short-lived
Eosinophils	2-4% of WBCs Weak phagocytes Effective against parasitic worms Anti-histamine properties
Basophils	0.5-1% of WBCs Release histamine (dilates BVs) & heparin (anti-coagulant) from granules
Lymphocytes	20-30% of WBCs 3 Types B-cells T-cells Natural killer cells
Monocytes	3-8% of WBCs 12-20um Kidney-shaped nucleus Leave blood &enter tissues; transform into macrophages which phagocytose microbes ‘Fixed’ or ‘wandering’
A macrophage extends a .............to pull in and engulf a bacterium.	pseudopod
Lymphatic System	Network of vessels which transport excess fluid away from interstitial spaces & return it to bloodstream Helps defend body against disease-causing agents.
Organs of the lymphatic system include?	Lymph nodes Spleen Thymus Tonsils
Parts of the Lymphatic System - Lymph?	A fluid similar to plasma but no plasma proteins
Lymphatic vessels (lymphatics)?	Carry lymph from peripheral tissues to the venous system
LYMPH NODES	Located along length of lymphatics, these filter lymph, trapping bacteria, etc. Lymphocytes in nodes attack & destroy microbes Swell during an infection due to ↑lymphocyte numbers.
Spleen	Largest lymphatic organ Site of B-& T-lymphocytes proliferation during infection. Phagocytosis of bacteria & old & damaged RBCs. Blood store –rupture of spleen causes severe blood loss & shock (low BP).
Thymus	2-lobed organ behind sternum. Site of T-cell maturation. Produces hormones which promote maturation of T-cells. Most active during early life-critical role in development of immune system before birth & during childhood. Reaches maximum size at puberty& shrinks thereafter.
Tonsils	Group of lymph nodes at back of throat Produce lymphocytes and antibodies which defend against swallowed or inhaled microbes
Non-specific Resistance - Physical barriers	Intact skin Mucous membranes Hairs in nostrils (filter) Cilia in trachea (sweep particles away)
Chemical barriers	Stomach acid:- strongly acidic gastric juice kills most bacteria swallowed in food Sweat /sebaceous glands:- secrete bacteriocidal & fungicidal substances Lysosyme:- powerful bacteriocidal enzyme in tears, saliva, nasal secretions
Natural Killer (NK)Cells	Non-specific type of lymphocyte which attack & destroy a variety of cancer cells & virus-infected cells. Bind to cancer cell, release perforin which perforates cell membrane, killing cell.
Interferons	Proteins produced & released by virus-infected cells. INFs diffuse to neighbouring uninfected cells & bind to receptors. Induce production of anti-viral proteins which prevent viral replication in healthy cells.
Fever (pyrexia)	Chemical (pyrogens) released from damaged tissue act on hypothalamus (thermostat). ‘Thermostat’ re-set to higher temp. Increased body temperature: Inhibits microbial growth Speeds up tissue repair.
Summary of non-specific defences - 2nd line of defense?	Phagocytosis Complement Inflammation Interferon Fever NK cells
Any foreign substance which triggers an immune response is called an ....... (e.g.bacteria, viruses, transplanted tissue, pollen ,etc)	Antigen
Immune system remembers a particular antigen & responds much faster on 2nd exposure. Immune system can recognise & remember millions of antigens that may invade body. 2 types of lymphocytes involved?	B-lymphocytes (B-cells) T-lymphocytes (T-cells)
B- & T-cells are derived from ?	stem cells in bone marrow.
Immature T-cells must pass to the.......where they gain specificity.	thymus
B Cells provide? Defend against?	Provide antibody-mediated immunity. Defends against antigens and pathogens in body fluids i.e. outside cells. When activated, become plasma cells which produce antibodies.
T Cells provide? Defend against?	Provide cell-mediated immunity. Defends against abnormal cells (cancer cells ,transplanted cells) and pathogens inside cells (e.g.viruses)
Each T or B cell: responds only to a ...... antigen ignores all others	Specific
On exposure to specific antigens, .......are activated & transform into ...... cells which produce ......... which inactivate the antigen. Antibodies are proteins-immunoglobulins They are y-shaped molecules with specific receptor sites to bind specific antigen Used to attack free bacteria & viruses in body fluids (i.e extracellular pathogens)	B-cells plasma cells antibodies
Cell-mediated immunity (T-cells)	Method used for attacking virus-infected cells, cancer cells ; transplanted cells. Specific T-cells are activated (sensitized) when antigen is presented to it by an antigen-presenting cell , usually a macrophage. Sensitized T-cells then enlarge, differentiate & divide into a clone. Within clone, there are 4 types of T-cells
Helper T-cells	Identify virus-infected cells (or foreign cells) by presence of ‘non-self’ antigens on cell membrane. Help activate cytotoxic T-cells which attach to & kill infected cells. Induce antibody production by B-cells. HIV specifically attacks Helper T-cells, resulting in suppressed immune response
Cytotoxic (killer) T-cells	Recognise ‘foreign’ cell by ‘non-self’ antigen displayed on surface of cell membrane. Attach to infected, cancer or transplanted cell & release a chemical (perforin) which bursts cell membrane.
Suppressor T-cells	Dampen down the immune response once the infection is overcome.
Active Immunity	Long-lasting protection resulting from exposure to a particular antigen. Results in production of antibodies , T-cells & memory cells. Can be acquired naturally following exposure to the disease-causing pathogen or artificially by injecting weakened version of antigen i.e. vaccination (e.g.MMR, etc).
Passive Immunity	Temporary, short-term protection gained by receiving ready-made antibodies produced by another person. Natural passive – mother’s antibodies protect fetus & new-born baby by crossing placenta and presence in breast milk. Artificial passive – injection of ready-made antibodies given for serious, life-threatening conditions –e.g. tetanus, rabies

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WBCs and Resistance to disease

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