1. The body’s defenders

2. Core concepts Infectious diseases are caused by pathogens
Nonspecific defenses against infection
Plants and animals have mechanisms that are not targeted to specific pathogens that help them combat infection
Skin and mucous membranes provide first-line barriers to infection
Phagocytic cells, inflammation, and antimicrobial proteins function as the second line of defense
Specific immunity arises from lymphocyte-antigen interactions
Lymphocytes provide the specificity and diversity of the immune system
Antigens interact with specific lymphocytes, inducing immune responses and immunological memory
Lymphocyte development gives rise to an immune system that distinguishes self from nonself
Immune responses take two forms: humoral and cell-mediated
Helper T-lymphocytes function in both humoral and cell-mediated immunity
Cytotoxic T-cells counter intracellular pathogens
B-cells make antibodies against extracellular pathogens
Memory B- and T-cells are responsible for faster and stronger secondary immune responses
Immunity in health and disease
Immunity can be achieved naturally or artificially
The immune system limits blood transfusion and tissue transplantation
Abnormal immune function can lead to disease
AIDS is an immunodeficiency disease caused by a virus

3. Keywords memory cell chemokines monocytes class I MHC class II MHC
clonal selection
complement fixation
complement system
cytokine
cytotoxic T cell
effector cell
eosinophils
helper T cell
histamine
HIV
humoral immunity
immunity
immunodeficiency disease
immunoglobulin
inflammatory response
interferon
interleukin
lysozyme
macrophages
major histocompatibility complex
mast cells
membrane attack complex
memory cell
monocytes
natural killer cells
neutrophils
nonspecific defense
opportunistic disease
passive immunity pathogen
perforin
phagocytosis
plasma cell
primary immune response
prostaglandins
pyrogens
Rh factor
secondary immune response
suppressor T cell
T cell
T cell receptor
target cell
tumor antigen
vaccine
ABO blood groups
active immunity
agglutination
AIDS
allergy
anaphylactic shock
antibody
antigen
antigen receptor
antigen-presenting cell
apoptosis
autoimmune disease
B cell
basophils
CD4
CD8
cell-mediated immunity

4. Pathogens and disease
Fungi
Viruses
Protozoa
Large parasites
Bacteria

5. Two major types of defenses
INNATE (NONSPECIFIC)
IMMUNITY
Rapid responses to a
broad range of microbes
ACQUIRED (SPECIFIC) IMMUNITY
Slower responses to
specific microbes
External defenses
Internal defenses
Skin
Mucous membranes
Secretions
Phagocytic cells
Antimicrobial proteins
Inflammatory response
Natural killer cells
Humoral response
(antibodies)
Cell-mediated response
(cytotoxic
lymphocytes)
Invading
microbes
(pathogens)

6. Innate (nonspecific) immunity First line: External defenses
Mucus, cilia
Tears
Mouth bacteria, saliva
Skin, oil, sweat, acidity
Intestinal flora
Gastric juice
Acid conditions

7. Innate immunity Second line: Internal defenses
Microbes
MACROPHAGE
Vacuole
Lysosome
containing
enzymes
Phagocytic cell
Innate immunity Second line: Internal defenses 1
Phagocytes
Attach to and ingest invading microorganisms
Initiate the inflammatory response
Macrophages – migrants or in lymph organs, lungs, kidneys, connective tissues
Antimicrobial proteins
Complement system – lysis of invading cells, triggers inflammation
Interferons – activate macrophages, prevent cell-to-cell spread of viruses
Defensins – secreted by macrophages to damage pathogens 2 3 4 5 6

8. 70%
chemotaxis 5%
1.5%
histamine

9. Innate immunity Second line: Internal defenses (con’t.)
Inflammatory response
Chemicals involved
Histamines
Prostaglandins
Chemokines
Pyrogens

10. Innate immunity Second line: Internal defenses (con’t.)
Natural killer (NK) cells
Attack virus-infected body cells and cancer cells
Apoptosis (cell death) in cells attacked
Coelomocytes and hemocytes – phagocytes in invertebrates

11. Specific (acquired) immunity Third line of defense
Lymphocytes
In blood and lymph
Types
B – cells – mature in marrow
T – cells – mature in thymus
Helper
Cytotoxic/Killer
Regulatory/Suppressor
Memory
Activated by cytokines from phagocytes
Display specificity to epitopes on antigens (antibody generator)
Have specific membrane- bound antigen-receptors

13. Two types of specific immune responses
B and T cells generate clones of
short-lived activated effector cells
long-lived memory cells

14. MHC molecules and T cell function
Class I MHC molecules
Most nucleated cells of the body
Infected/cancerous cells display parts of foreign antigens on surfaces
Recognized by cytotoxic T cells
Class II MHC molecules
Dendritic cells, macrophages, B cells (APCs) display phagocytized antigen fragments on surfaces
Recognized by helper T cells
T cells that have receptors for self-molecules are destroyed  self-tolerance

15. Clonal selection antigen-driven cloning of lymphocytes
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Clonal selection antigen-driven cloning of lymphocytes
Antigen binds to receptor on lymphocyte
Lymphocyte is activated
Thousands of clones specific for the antigen are produced

16. Antibody action

17. Immunity – memory cells initiate a faster, more efficient response upon reinfection

18. Active immunity Passive immunity Own system develops antibodies
Develops naturally in response to infection
Develops following immunization (artificial immunity)
Long-lasting protection but may take a long time
Passive immunity
Antibodies are passed from mother to fetus via the placenta
Antibodies are passed from mother to infant via breast milk (colostrum)
Antibodies may be injected into a nonimmune person (artificial immunity)
Immediate, short-term protection

19. Blood groups and transfusions
Problems with transfusions and transplants
Antigens on RBC’s will determine a person’s blood type: A, B, AB, O blood
Another RBC antigen: Rh factor  Rh+ or Rh-

20. Immune disorders/diseases
Allergies – hypersensitive responses to antigens called allergens
Autoimmune diseases – immune system loses tolerance for self and turns against certain molecules of the body (SLE, diabetes type I, rheumatoid arthritis)
Immunodeficient diseases
Inborn or primary (severe combined ID)
Acquired or secondary
AIDS – HIV attacks CD4 molecules on helper T cells, macrophages, dendritic cells

21. IgE antibodies bind to
receptors or mast cells. 1
On subsequent exposure to the
same allergen, IgE molecules
attached to a mast cell recog-
nize and bind the allergen. 2
Degranulation of the cell,
triggered by cross-linking of
adjacent IgE molecules,
releases histamine and other
chemicals, leading to allergy
symptoms. 3
Allergen
IgE
Histamine
Granule
Mast cell