Nonspecific Host Defenses

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Nonspecific Host Defenses
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Host Defenses

• Susceptibility lack of resistance to a disease
• Immunity
• Innate versus Adaptive
• Innate against any pathogen
• Adaptive resistance to a specific pathogen
• Resistance
• Nonspecific Resistance
• Specific Resistance
• First line skin and mucous membrane
• Second line non specific host defenses
  (phagocytes, inflammation, fever and
  antimicrobial substances)
• Third line specific host defense (lymphocytes
  B or T cells and antibodies)

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Host Defenses
Figure 16.1
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Overview of the immune system
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Toll receptors

• http//student.ccbcmd.edu/courses/bio141/lecguide/
  unit1/prostruct/toll/toll.html
• http//www.pubmedcentral.nih.gov/botrender.fcgi?bl
  obtypehtmlartid207104

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Toll Receptors

• Host cell recognizes the pathogen with pattern
  recognition receptors/molecules (PRMs)
• Pathogens have pathogen-associated molecular
  patterns (PAMPs)
• Sugars, proteins, lipids, nucleic acids
• Produced by pathogen not by the host
• Recognized by Toll receptors

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First Line of Defense Fig 16.2

• Skin
• Epidermis (outer layer)
• Epithelial cells with keratin (protective
  protein)
• Dermis
• Mucous membrane
• Less protection than skin
• Fluid nature
• Similar to skin
• Epithelial layer with underlying connective tissue

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First Line of Defense

• Mechanical Factors
• Lacrimal apparatus
• washes eye and drains through nose
• Produces tears
• Saliva
• Washes microbes
• off, dilutes microbes
• in mouth and prevents
• colonization

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First Line of Defense

• Mechanical Factors
• Mucous membrane covered by cilia
• Ciliary escalator
• Propel microorganisms trapped in the mucus are
  transported towards the throat
• Epiglottis
• Covers larynx during swallowing
• Prevents microorganisms from entering the lower
  respiratory tract
• Urination microbes flow out
• Vaginal secretions
• microbes flow out

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First Line of Defense

• Chemical Factors
• Sebum
• Produced by sebaceous glands
• Unsaturated fatty acids (hydrophobic) fights
  off fungi
• Forms protective film over the skin
• Low pH (pH 3-5) of skin
• Perspiration
• Sweat glands
• Lysozyme destroys bacteria
• Gastric juice
• HCl, enzymes and mucous (very low pH 1.2-3.0)
• C. botulinum, S. aureus, and H. pylori can
  survive
• Ulcers and H. pylori
• Transferins
• Iron binding proteins found in blood
• Reduce amount of available iron

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First Line of Defense

• Normal Flora
• Microbial antagonism between normal flora and
  pathogens
• Preventing the outgrowth of harmful organisms by
  preventing colonization/invasion
• Competition for nutrients and O2, pH, and
  bacteriocins
• Competitive exclusion
• The flora are called commensal or mutualistic
  symbionts of the host.
• Ex. Intestinal flora

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Cells in the blood and bone marrow
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Blood cells

• Erythrocytes (RBCs)
• Transport oxygen and carbon dioxide
• Leukocytes (WBCs)
• Defensive cells
• Platelets
• Proteins involved in clotting

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Different types of blood cells
Table 16.1 (1 of 2)
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Different types of blood cells
Table 16.1 (2 of 2)
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Differential White Cell Count

• Percentage of each type of white cell in a sample
  of 100 white blood cells.
• Determine stages of infection
• Leukocytosis (increase) versus leukopenia
  (decrease)

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WBC (Leukocytes)

• Granulocytes
• All involved in 2nd line of defense
• Granular appearance
• Types
• Neutrophils motile phagocytes early stages of
  infection
• Basophils not phagocytic release histamine
  important in inflammation and allergic responses
• Eosinophils motile phagocytes attack helminths
  release toxins to destroy before ingesting large
  helminth
• Dendritic cells Initiate adaptive immunity
  response

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WBC (Leukocytes)

• Agranulocytes
• Monocytes must mature into macrophages before
  they are phagocytic (in tissues)
• Second line of defense
• In blood and lymph?monocytes
• In tissue and lymph?macrophage
• Wandering versus fixed macrophage in lymph
  (permanent residents, Kuppfer cells in liver)
• Swelling in lymph nodes due to monocyte
  maturation during initial infection
• Also help dispose of old blood cells in lymph
• Are there mononcytes in the brain?

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WBC (Leukocytes)

• Agranulocytes
• Lymphocytes not phagocytic involved in
  specific immunity
• Occur in lymphoid tissues of lymphatic system
  (i.e. tonsils, spleen, thymus gland, etc.)
• Third line of defense (Chapter 17)