The Immune System

1
24

• The Immune System

2
Immune System Functions

• Protects from pathogens and foreign molecules
• Parasites
• Bacteria
• Viruses
• Removes dead or damaged cells
• Attempts to recognize and remove abnormal cells

3
Immune System Pathologies

• Incorrect responses
• Autoimmune disease (Type 1 diabetes)
• Overactive responses
• Allergies
• Lack of response
• Immunodeficiency disease (AIDS)

4
Pathogens Bacteria and Viruses
5
Viral Structure and Replication
Figure 24-1b
6
Body Defenses Two Lines

• Physical and chemical barriers
• First line of defense
• Skin, epithelial linings, and cilia
• Acids, mucous, and lysozymes
• Immune defenses
• Second line of defense
• Innate, non-specific, immediate response
• Acquired attack a specific pathogen (antigen)

7
Steps in an Immune Response

• Detect and identify invader/foreign cells
• Communicate, alarm, and recruit immune cells
• Coordinate response among all participants
• Suppress or destroy invader

8
Lymphatic System

• Primary tissues
• Bone marrow and thymus
• Encapsulated tissues
• Lymph nodes and spleen
• Lymph vessels
• Diffuse tissues

9
Lymphatic System Anatomy
Figure 24-2a
10
Lymphatic System Anatomy
Figure 24-2b
11
Key Cells of the Immune System

• Leukocytes (white blood cells)
• Eosinophils
• Basophils and mast cells
• Neutrophils
• Monocytes and macrophages
• Lymphocytes and plasma cells
• Dendritic cells

12
Figure 24-4
13
Immune Cell Groups

• Morphological group
• Granulocytes
• Functional group
• Phagocytes, cytotoxic cells, and
  antigen-presenting cells (APCs)
• Mononuclear phagocyte system

14
Immune Cells Function

• Eosinophils
• Allergic reactions
• Parasitic diseases
• Basophils
• Release histamine
• Inflammation

15
Immune Cells Function

• Neutrophils
• Ingest bacteria
• Release cytokines
• Monocytes
• Mature to macrophages
• Phagocytic
• APCs

16
Immune Cells Function

• Lymphocytes
• Acquired immunity
• Dendritic cells
• Activate lymphocytes

17
Antigen-Presenting Cells
Figure 24-5
18
Innate Immunity Nonspecific

• Physical and chemical barriers
• Phagocytosis macrophages, neutrophils, natural
  killer (NK) cells
• Engulf and digest tagged cells
• Inflammatory response

19
Innate Immunity Phagocytosis
Figure 24-6a
20
Innate Immunity Phagocytosis
Figure 24-6b
21
Phagosomes

• Lysosomal enzymes digest pathogens that have been
  enclosed in phagosomes

Figure 24-7
22
NK cells

• Eliminate virus-infected and tumor cells
• Secrete interferons
• Interferon-alpha and interferon-beta
• Prevent viral replication
• Interferon-gamma
• Activates macrophages and other immune cells

23
Inflammatory Response

• Attract immune cells and chemical mediators to
  site of infection
• Produce physical barrier to prevent infection
  from spreading
• Promote tissue repair

24
Inflammatory Response

• Histamines from mast cells
• Swelling, edema, vasodilation
• Interleukins
• Fever, blood vessels more permeable to white
  blood cells and proteins, acute-phase proteins

25
Inflammatory Response

• Bradykinin
• Pain and swelling
• Complement cascade
• Membrane attack complex

26
Inflammatory Response

• Action of a membrane attack complex

Figure 24-8
27
(No Transcript)
28
Acquired Immunity Antigen-Specific

• T lymphocytes
• Helper T cells
• Cytotoxic T cells
• B lymphocytes
• Plasma cells
• Memory cells
• NK cells

29
Acquired Immunity Antigen-Specific

• Naïve lymphocytes
• Clonal expansion
• Effector cells
• Memory cells

30
Acquired Immunity Antigen-Specific

• How clonal expansion leads to immunologic memory

Figure 24-10 (1 of 4)
31
Acquired Immunity Antigen-Specific
Figure 24-10 (2 of 4)
32
Acquired Immunity Antigen-Specific
Figure 24-10 (3 of 4)
33
Acquired Immunity Antigen-Specific
Figure 24-10 (4 of 4)
34
B lymphocytes Humoral Immunity

• Immunoglobulins
• Plasma and memory cells
• Primary and secondary response

35
B lymphocytes Humoral Immunity

• Memory in the immune system

Figure 24-11
36
Plasma Cells Antibodies

• Five classes
• IgG-75 of plasma antibody in adults produced in
  secondary immune response Maternal IgGs cross
  placental membrane and give infants immunity in
  the first few months of life IgGs activate
  complement
• IgA-found in external secretions such as tears,
  saliva, intestinal and bronchial mucus, breast
  milk
• IgE-allergic responsewhen mast cell receptors
  bind with IgEs and antigen, the mast cells
  degranulate and release histamine
• IgM-primary immune responses antibodies that
  react with blood group antigens IgMs activate
  complement
• IgD-IgD antibody proteins appear on the surface
  of B lymphocytes along with IgM

37
Antibody Structure

• Light and heavy chain
• Fab region-form antigen binding sites that confer
  antibody specificity
• Fc region-determines the Ig class

38
Plasma Cells Antibody Structure
Figure 24-12
39
Functions of Antibodies
Figure 24-13
40
T Lymphocytes Cell-Mediated

• T cell receptors
• Cell activated by antigen
• Major histocompatibility complex (MHC)

41
T Lymphocytes Cell-Mediated

• Activation of T lymphocytes

Figure 24-15
42
Major Histocompatibility Complex

• Family of membrane protein complexes encoded by a
  specific set of genes first identified as
  responsible for tissue transplant rejection
• MHC proteins combine with fragments of antigens
  that have been digested within the cell, and the
  MHC complex is inserted into the cell membrane by
  exocytosis.
• MHC class I-found on all nucleated cells
• Cytotoxic T cells target MHC class I and kills it
• MHC class II-found on macropphages, B
  lymphocytes, and dendritic cells
• Helper T cells recognize MHC Class II and secrete
  cytokines that enhance immune response

43
T Lymphocytes Cell-Mediated

• Roles of T lymphocytes and NK cells in
  cell-mediated immunity

Figure 24-16
44
Defenses against Bacteria

• Immune responses to extracellular bacteria

Figure 24-17
45
Figure 24-17
46
Defenses against Viruses

• Immune responses to viruses

Figure 24-18
47
Figure 24-18
48
Allergic Responses

• First exposure
• Sensitization
• Activation, clone B cells, form antibodies and
  memory cells
• Re-exposure
• Many antibodies, activated T cells, intensified
  response, inflammation

49
Figure 24-19
50
Blood Types

• Antigens on RBCs
• A, B, AB or none (O)
• Antibodies in plasma
• Anti A, anti B, anti AB
• Rh antigens and antibodies

51
Blood Types ABO Blood Groups
Figure 24-20a
52
Blood Types ABO Blood Groups
Figure 24-20b
53
Autoimmune Diseases
54
Neuro-Endocrine-Immune Interaction

• Not fully understood
• Neuroimmunomodulation
• Common signal molecules and receptors
• Overlapping responses
• Fight or flight
• Chronic stress

55
Neuro-Endocrine-Immune Interaction

• Model for interaction between nervous, endocrine,
  and immune systems

Figure 24-21