Host defenses: Immunity

1
Ch. 16 Nonspecific Defenses of the Host

• Host defenses Immunity
• Innate Immunity (nonspecific)
• First-line defense
• Second-line defense
• Acquired Immunity (specific)
• Third-line defense
• Discussed in Ch. 17

2
First-line Defense

• Mechanical Factors
• Chemical Factors
• Normal flora

3
Mechanical Factors

• Skin
• Epidermis consists of tightly packed cells
• Keratin, a protective protein
• Mucous Membrane
• Ciliary escalator Microbes trapped in mucus are
  transported away from the lungs
• Urine and vaginal secretions Flows out
• Glands
• Lacrimal apparatus Washes eye
• Saliva Washes microbes off

4
Chemical Factors

• Sebaceous glands of skin secrete sebum Fatty
  acids w/ pH of 3-5
• Gastric juices of stomach acidic pH (1.2-3)
• Perspiration, tears, saliva, and tissue fluids
  secrete lysozymes and peroxidase enzymes
• Transferrins in blood compete with bacteria for
  the binding of iron
• Nitric oxide (NO) inhibits ATP production of
  bacteria

5
Normal Flora

• Microbial synergism
• Microbial commensalism
• Microbial antagonism

6
Second-line defense

• White Blood Cells
• Granulocytes
• Mononuclear Phagocytes (monocytes)
• Lymphocytes
• Phagocytosis
• Other Blood Components
• Inflammation fever
• Complement system
• Lymphatic System

7
Formed Elements in Blood
8
White Blood Cells

• Neutrophils Phagocytic
• Basophils Produce histamine
• Eosinophils Toxic to parasites, some
  phagocytosis
• Monocytes Phagocytic as mature macrophages
• Fixed macrophages in lungs, liver, bronchi
• Wandering macrophages roam tissues
• Lymphocytes Involved in specific immunity

9
Differential WBC count
Percentage of each type of white cell in a sample
of 100 white blood cells
Percentage of each type of white cell in a sample
of 100 white blood cells
Percentage of each type of white cell in a
sample of 100 white blood cells
10
Phagocytosis

• Neutrophils
• Macrophages
• Produce cytokines
• Interact with T helper cells activated
  macrophages
• Help form granulomas
• Process of phagocytosis

11
Process of phagocytosis
Figure 16.8a
12
Microbial Evasion of Phagocytosis
13
Other Blood Components

• Red Blood Cells, Platelets, Plasma
• Important role in inflammatory response
• Major function is blood clotting
• Serum
• Clear yellowish fluid that contains proteins
• Albumin
• Globulin gamma portion contains antibodies
• Complement system
• Interferons glycoproteins

14
Inflammation

• Cardinal signs Redness, Pain, Heat, Swelling
  (edema)
• Complement cascade (acute-phase proteins
  activated cytokine, kinins)
• Vasodilation (histamine, kinins, prostaglandins,
  leukotrienes)
• Margination and emigration of WBCs
• Tissue repair

15
Chemicals Released by Damaged Cells
16
Inflammation process
Figure 16.9a, b
17
Inflammation process
Figure 16.9c, d
18
Fever

• Physiological response to infections
• Pyrogens
• Endogenous fever-inducing cytokines
• Exogenous bacterial endotoxins
• Hypothalamus controls temperature
• releases prostaglandins that reset the
  hypothalamus to a high temperature
• Body increases rate of metabolism and shivering
  to raise temperature
• High temperature inhibits pathogen growth

19
The Complement System

• Serum proteins activated in a cascade.
• Complement activation
• Classical
• Alternative
• Lectin

Figure 16.10
20
Classical Pathway
Figure 16.13
21
Alternative Pathway
Figure 16.14
22
Lectin Pathway
Figure 16.15
23
Interferons (IFNs)

• Alpha IFN Beta IFN Cause cells to produce
  antiviral proteins that inhibit viral replication
• Gamma IFN Causes neutrophils and macrophages to
  phagocytize bacteria

24
Interferons (IFNs)
New viruses released by the virus-infected host
cell infect neighboring host cells.
5
2
The infecting virus replicates into new viruses.
AVPs degrade viral m-RNA and inhibit protein
synthesis and thus interfere with viral
replication.
6
Viral RNA from an infecting virus enters the cell.
1
The infecting virus also induces the host cell to
produce interferon on RNA (IFN-mRNA), which is
translated into alpha and beta interferons.
3
Interferons released by the virus-infected host
cell bind to plasma membrane or nuclear membrane
receptors on uninfected neighboring host cells,
inducing them to synthesize antiviral proteins
(AVPs). These include oligoadenylate synthetase,
and protein kinase.
4
Figure 16.16
25
Lymphatic System

• Lymphatic vessels
• 1º lymphoid organs
• Thymus
• Bone marrow
• 2º lymphoid organs
• Lymph nodes
• Adenoids
• Tonsils
• Spleen
• Appendix
• SALT
• MALT