Immune System

• Types of immune response

  • Innate Immune Response
  • Adaptive Immune Response
• Innate Immune Response


  • Present before any exposure to pathogens and effective from birth
  • Involves nonspecific responses to pathogens
  • Consists of external barriers plus internal cellular and chemical defenses
• Innate immunity defenses


  • Barrier defenses like skin, mucous membranes and secretions
  • Internal defenses like phagocytic cells, natural killer cells, antimicrobial proteins, inflammatory response
• Adaptive Immune Response


  • Develops after exposure to agents like microbes, toxins, or other foreign substances
  • Involves a very specific response to pathogens (for vertebrates only)
• Adaptive immune response mechanisms

  • Humoral response - production and secretion of antibodies
  • Cell mediated response - occurs when cytotoxic cells defend the body against infection; development of B and T cells, memory cells and plasma cells

  
• B cells


  • Develop and mature in the bone marrow
  • Activated when they encounter antigen in the lymph nodes
  • Produce antibodies that recognize and bind to specific antigens; each B cell produces only one antibody which recognizes only one kind of antigen (specificity)

  
• Antibody types


  • IgM - first antibody produced, coats pathogens, promotes endocytosis
  • IgG - major antibody, activates immune response and leads to neutralization and destruction of pathogen
  • IgA - important antibody for mucosal immune response, prevents pathogens from crossing the epithelium and entering the blood stream
  • IgE - activates mast cells and leads to the production of histamine, associated with allergies
  • IgD - serves as antigen receptors

  
• T cells


  • Produced in bone marrow, mature in thymus
  • Activated when they encounter antigens in lymph nodes, need to recognize antigen in context of MHC molecules
  • Cytotoxic T cells kill virus-infected cells
  • Helper T cells secrete proteins to help other immune cells
  • Regulatory T cells control and turn off immune response

  
• Types of animals based on body fluid osmolarity

  • Osmoconformers - allow body fluid osmolarity to match environment
  • Osmoregulators - keep body fluid osmolarity different from environment
• Types of nitrogenous wastes excreted by animals


  • Ammonia - primary waste for aquatic invertebrates, teleosts, larval amphibians
  • Urea - produced by mammals, some amphibians, reptiles, fishes, invertebrates
  • Uric acid - excreted by birds, insects, terrestrial reptiles
• Excretory systems in invertebrates


  • Cell surface/membrane
  • Contractile vacuole
  • Protonephridia or Flame Bulb System
  • Metanephridia
  • Malpighian Tubules
• Mammalian urinary/excretory system


  • Consists of kidneys, ureters, bladder, urethra
  • Kidneys serve for osmoregulation and excretion, composed of renal capsule, cortex, medulla, nephrons, renal pelvis
  • Each kidney has 1.3M nephrons, 80km long if connected
  • 1,600 liters of blood pass through kidneys daily, 180 liters become filtrate, 1.5 liters excreted as urine
  • Over 99% of water and almost all nutrients reabsorbed
• Label the picture below.

  A) Antibody

  B) Antigen receptor

  C) B cell

  D) Epitope

  E) Antigen

  F) Pathogen

  
• IgM


  The first antibody produced. It coats the pathogen and promotes endocytosis by macrophages.
• IgG


  A major antibody produced. It activates the other parts of the immuneresponse and leads to neutralization and destruction of pathogen.
• IgA


  Important antibody for the mucosal immune response. It prevents pathogens from crossing the epithelium and entering the blood stream.
• IgE


  Ativates mast cells and leads to the production of histamine, which is why it is also associated with allergic reactions.
• IgD


  Serves as receptors for antigens.
• Ammonia

  • readily soluble in water but is also highly toxic
  • can be excreted from the body only in dilute solutions
• Urea

  • formed by combining ammonia with bicarbonate ion (HCO3 ̄) and converting the product into urea
  • about 100,000x less toxic than ammonia
• Uric acid


  largely insoluble in water and it is excreted as a semisolid paste or precipitate with very little water loss
• Label the picture below.

  A) Antibody C

  B) Antibody B

  C) Antibody A

  D) Antigen

  
• Excretory systems in invertebrates

  • Cell surface or cell membrane
  • Contractile vacuole
  • Protonephridia or Flame Bulb System
  • Metanephridia
  • Malpighian Tubules
• Cell surface or cell membrane

  allows passage of wastes in unicellular organisms
• Contractile vacuole


  a specialized cytoplasmic organelle in many freshwater

  protists (e.g. Paramecium) that expels excess water out of the cell to prevent lysis
• Protonephridia or Flame Bulb System

  network of tubules that lack internal openings but have external openings at the body surface called nephridiopores such as in the flatworm, Dugesia.

  1. The smallest branches of the tubule network end with a large cell called aflame bulb or cell
  2. Water and solutes in body fluids enter the flame cell and get filtered
• Metanephridia


  the excretory tubule of most annelids and adult mollusks.

  1. The tubular network has a funnel-like internal opening called a nephrostome that collects body fluids
  2. The bladder stores the nitrogenous wastes as urine and later on excreted fromthe body surface via the nephridiopore
• Malpighian Tubules


  the excretory tubules of insects and other terrestrial

  arthropods attached to their digestive tract (midgut)

  1. The tubules have ends that are immersed in the hemolymph (circulatory fluid) while the distal ends empty into the gut
• Kidneys are composed of:

  • renal capsule
  • cortex
  • medulla
  • nephrons
  • renal pelvis
• renal capsule


  the outer coat of connective tissue
• cortex


  the zone near the capsule consisting of blood vessels and nephrons
• medulla


  inner zone also consisting of blood vessels and nephrons
• nephrons


  the functional units of the kidney where urine is formed
• renal pelvis


  central cavity in the kidney where urine coming from the nephrons is channeled before going to the ureter
• Immunology is a branch of biology that covers the study of immune systems in all organisms.
• Internal defenses of the innate immune response consist of phagocytic cells, natural killer cells, antimicrobial proteins (interferons; the complement system) and the inflammatory response (that involves histamines, mast cells and cytokines).
• Barrier defenses like the skin, mucous membranes and secretions. In humans and in most vertebrates, the skin with other ectodermal derivatives is the first line of defense against infection.