immunity

• plasma contains

  blood proteins, glucose, vitamins, minerals, dissolved gases, waste products
• blood proteins


  albumins: maintain osmotic pressure to draw water back into capillaries

  globulins (immunogloulins): proteins (antibodies) that help in immunity by binding onto and tagging foreign antigens

  fibrinogens: blood clotting
• during conditions requiring more RBCs

  the kidneys release the hormone erythropoietin that stimulates differentiation of hematopoietic stem cells into RBCs (erythropoiesis).
• 2 types of leukocytes

  granulocytes: contains granules within cytoplasm

  agranulocytes: no granules (lymphocytes)
• blood clotting

  1) platelets (thrombocytes) produced by fragmentation of cytoplasm from large nucleated cells (megakaryoctes) in bone marrow.

  2) when the blood vessel is damaged, platelets activated and clump together to form a plug at the injury site. the shape changes from round to spiny to help trap more platelets at the site. starts to release thromboplastin protein

  3) thromboplastin interacts with calcium ions to activate inactive plasma protein prothrombin into enzyme thrombin

  4) thrombin activates soluble protein fibrinogen to form insoluble threads (fibrin)

  5) fibrin crosslink and interact to form mesh scaffold to trap more RBCs and platelets at the site to stop bleeding

  6) air exposure allows it to dry into a scab
• thrombus


  blood clot that seals a blood vessel which leads to no o2 in tissues leading to tissue death. cerebrae thrombosis leads to a stroke and coronary thrombosis leads to a heart attack. am embolus (embolism) is a dislodged clot which travels through body and lodges in vital organ
• blood types

  type a: antigen a, antibody anti-B, donors are A and O

  type b: antigen b, antibody anti-A, donors are b and o

  type ab: antigens a and b, no antibodies, donors are any

  type o: no antigens, antibodies anti- a and b, donor is o
• first line of defense

  mainly physical, non-specific. physical barriers like skin and chemical barriers like acidic secretion (e.g. sebaceous glands associated with hair follicles secret sebum which maintains moisture of skin and lowers pH).

  
  

  a lysozyme is an antimicrobial enzyme present in tears, saliva, mucuous secretions, and sweat which can destroy cell walls of bacteria. HCl and other protein-digesting enzymes also present in stomach which destroy microbes entering with food. mucus can trap particles and microbes.
• innate immune system

  barriers, chemicals, phagocytic cells. respond to broad categories of pathogens and do not change during organism's lifetime.
• second line of defense


  non-specific but more direct as WBCs can engulf invading microbes.

  
  

  monocytes are agranulocytes that develop into phagocytic macrophages. neutrophils are phagocytic granulocytes that release lysozomal enzymes to digest both invader and itself following phagocytosis.

  
  

  results in pus which consists of protein fragments, dead WBCs, and digested invaders.

  
  

  inflammatory response: results in:

  
  

  1) heat and redness (vasodilation and flow of blood to capillaries at site)

  2) swelling: movement and accumulation of plasma and WBCs to tissues at site

  3) pain: release of chemicals called prostaglandins that simulate nerve endings (signal to protect wound)
• third line of defense

  more specific. macrophages which are permanently in spleen, lymph nodes, other tissues of lymphatic system can detect foreign antigens and invading microbes as blood is filtered through lymphatic system. detection of microbes activates compliment proteins in plasma which can cause perforation in membranes of pathogens or induce apoptosis (cell death) leading to lysis.
• 2 categories of lymphocytes

  t cells: produced in bone marrow, mature in thymus gland. identify microbes by antigenic markers, signals b-cells

  
  

  b cells: produced and mature in bone marrow. once activated, produces one specific type of antibody only that is expressed on cell membrane. can differentiate into super antibody producing cells (plasma cells). can also differentiate into memory b cells which allow body to recognise antigens that is has previously seen
• 4 types of t cells

  helper: activate b cells to produce antibodies or activate macrophages or activate cytotoxic t cells

  
  

  cytotoxic (killer): release cytotoxins that cause infected cells to undergo apoptosis

  
  

  memory: more rapid response to previously encountered antigen and associated pathogen

  
  

  suppressor (regulatory): downregulate t cell induction and proliferation to maintain self tolerance to self-antigens and prevent autoimmune responses
• recognition of harmful antigens

  1) t cells look for invaders

  2) macrophages attack and engulf, digesting invader and expressing antigens on cell membrane (antigen-presenting cells - either macrophages, dendritic cells or b cells). the antigen is expressed as a major histocompatibility complex molecule (surface protein)

  3) helper t cell then interacts with MHC through t cell receptor and releases chemical messenger called lymphokine

  4) this causes b cells to produce antibody for antigen and undergo cellular division, producing a clonal army of identical antibody producing b cells (clonal selection)

  5) helper t cell also activates killer which punctures cell membrane of cells containing the antigen.

  6) when infection is controlled, suppressor t shuts down the immune response to restore conditions to normal.
• viruses

  microbes that require host cells to replicate and enter host cells by binding onto host receptor sites. antibodies bind onto antigenic sites on the viruses. this leads to neutralisation, where the virus cannot interact with the host cell, and also makes pathogens more recognisable to phagocytes so they are readily engulfed (epsonisation)
• antibiotics

  take advantage of differences that exist between pathogen and native cells. bacteria are prokaryotic cells so they have different structures than eukaryotic, such as having peptidoglycan cell walls, 70S ribosomes, etc.
• antibiotic resistance

  overprescriptions, non-compliance (not completing), and improper use (in animal feedstocks as growth stimulants & in hospital settings) lead to selection for resistant strains.
• virus definition

  intracellular parasites

  1) infect cells and utilise their cellular machinery to replicate

  2) small (20-200 nm in diameter)

  3) no cytoplasm and nucleus

  4) fixed size

  5) nucleic acid and capsid (protein coat)

  6) some may have a lipid envelope derived from host cell membrane upon lysis or budding (where they exit from host cell)

  7) no enzymes (no metabolic reactions) OR very few that are involved in infection
• small pox is the only human disease that has been completely eradicated

  1) only humans can catch and transmit smallpox

  2) symptoms emerge quickly and are readily visible --> allows rapid vaccination of all individuals that have come into contact with the affected individual

  3) immunity generated for smallpox is long lasting and smallpox virus has low mutation rate
• allergies

  immune system mistakes harmless antigens for harmful invaders. results in a hyper over-active immune response accompanied by mucus secretions and tissue swelling. severe reactions can cause swelling of air passages leading to anaphylactic shock. cells that detect danger release bradykinin which stimulates release of histamine from mast cells and WBCs called basophils. histamine causes increased capillary permeability which initiates welling and inflammatory response.
• autoimmune diseases

  making antibodies against body's own cells. drugs that weaken immune system or old age can increase r5isk of autoimmune conditions.

  
  

  mutated t and b cells held in check by suppressor, signal for macrophage destruction. failure of these cells results in autoimmune disease e.g. rheumatoid arthritis (joints and connective tissue) type i diabetes which attacks insulin producing cells.
• organ transplant rejection

  organs and tissues have distinctive protein markers (MHCs), which must match donor to recipient to avoid rejection of organs and tissues by recipient's immune system. immunosuppressant drugs can be given to limit rejection but this increases risk of infection by pathogens.