Nonspecific Defenses of the Host

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Microbiology
Chapter 16
updated 6 years ago by kjansen01
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1

Resistance

Ability to ward off disease

2

Susceptibility

Lack of resistance to a disease

3

Nonspecific resistance

Defenses against any pathogen

4

Specific resistance

Immunity, resistance to a specific pathogen

5

First line of defense

  • Skin membranes
  • Normal microbiota
6

Second line of defense

  • Phagocytes
  • Inflammation
  • Fever
  • Antimicrobial substances
7

Mechanical Factors: Skin

  • Tightly packed cells in epidermis packed with keratin
  • Shedding of skin and microbes
8

Mechanical Factors: Mucous Membranes

  • Not as effective as skin
  • Cilliary escalator: Microbes trapped in mucous and transported away from the lungs
  • Lacrimal apparatus: washes eye
  • Saliva: washes microbes off
  • Urine and Vaginal secretions: flow out
9

Chemical Factors: Skin

  • Fatty acid in sebum (low pH of 3-5)
  • Lysozyme: perspiration, tears, saliva, tissue fluids
  • Gastric juice (low pH of 1.3-3.0)
  • Transferrins in blood find iron
10

Microbial antagonism/Competitive exclusion

Normal microbiota with pathogens

11

Phagocytosis

  • Ingestion of microbes/ particles by a cell
  • Performed by phagocytes
12

Leukocytes

White blood cells

13

Granulocyte

Large granules in cytoplasm visible under a light microscope

14

Agranulocyte

Have granules, but not visible under light microscope

(Nonsensical naming)

15

Types of Granulocytes

  • Neutrophils (60%-70%)
  • Basophils (0.5%-1%)
  • Eosinophils (2%-4%)
16

Neutrophils

  • "First responders at crime scene"
  • Highly phagocytic and motile
  • Leave blood, enter tissue that is infected and destroys microbes and foreign particles
17

Basophils

  • Role is unclear
  • Release histamine
18

Eosinophils

  • Attach to outer surface of parasites and discharge peroxide ions that destroy them
19

Types of Agranulocytes

  • Monocytes
  • Lymphocytes
20

Monocytes

  • "Detective if first responders can't handle it"
  • Phagocytic as mature macrophage
21

Lymphocytes

  • "Military, the last defense, most strong and most harmful"
  • T cells and B cells
  • Are not phagocytic
  • Key role in specific immunity
22

Differential White Cell Count

% of each type of WBC in a sample of 100 WBC

23

Action of Phagocytic cells

  • Neutrophils and monocytes will migrate to infected area
  • Granulocytes dominate initially
  • Monocytes mature into macrophages and dominate after progression of infection
24

Chemotaxis

  • Chemical attraction
  • Microbial products
  • Components of WBC
  • Peptides from complement
25

Adherence

  • Attachment of MO
  • M proteins and capsules prohibit attachment
  • Opsonization: enhancement of phagocytosis by coating with certain proteins
26

Inflammation

  • Redness
  • Swelling
  • Heat
  • Pain
27

Vasodilation

  • Increased blood flow
  • Increased permeability of BV
  • Prostaglandins & Leukotrienes
28

Margination

Phagocytes stick to inner surface of BV

29

Emigration

Diapedisis-Phagocytes move out of BV and into tissues

30

Fever

  • Above 37 C
  • Hypothalamus releases prostaglandins to set high temp
  • Body increases metabolism
  • Gram - endotoxin cause phagocytes to release interleukin 1
  • When IL-1 is eliminated, body temp falls
31

Advantages of fever

  • Increased productivity of T-lymphocytes
  • Increased effect of interferons
  • Increased tissue repair
32

Anti-Microbial Substances

  • Complement
  • Phagocytosis
  • Interferon
33

Complement System

Three PWs

  • Classical
  • Alternative
  • Lectin

Serum proteins involved in lysis and phagocytosis of bacteria

34

Interferons

  • Interfere with viral multiplication
  • Host cell specific but not virus specific
  • Disadvantages: only effective for short periods of time, when injected there are serious and sometimes toxic side effects, does not affect cells already infected