1. Immune System

2. Overview of Vertebrate Defenses
INNATE IMMUNITY
Rapid responses to a
broad range of microbes
ADAPTIVE (ACQUIRED)
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)
non specific
all plants and animals
pathogen-specific
only in vertebrates
involves B and T cells

3. Innate Immunity
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4. Avenues of Attack Attack from Outside Attack from inside
animals are a tasty nutrient- & vitamin-packed meal
cells are packages of macromolecules
animals must defend themselves against invaders (pathogens)
viruses
HIV, flu, cold, measles, chicken pox
bacteria
pneumonia, meningitis, tuberculosis, Lyme disease
Fungi
yeast (athlete’s foot)
Protists
amoeba, malaria
Attack from inside
cancers = abnormal body cells

5. Innate Immunity
Cellular innate defenses involve specific toll- like receptors: Recognize molecules common to a set of pathogens calling phagocytic white blood cells (WBC) to engulf recognized pathogen.

6. Innate Immunity 1st Line: Non Specific Barriers Barrier skin Traps
mucous membranes, cilia,
hair, earwax
Elimination
coughing, sneezing, urination, diarrhea
Unfavorable pH
stomach acid pH 2, sweat, saliva, urine
Lysozyme
enzyme digests bacterial cell walls
tears, sweat

7. Bacteria being engulfed Macrophage destroying yeast
Innate Immunity
2nd Line: Non – specific patrolling cells and proteins
attack pathogens, but don’t “remember” for next time
1. leukocytes
phagocytic white blood cells
macrophages, neutrophils, natural killer (NK) cells
2. complement system
proteins that destroy cells
3. inflammatory response
increase in body temp.
increase capillary permeability
attract macrophages
Bacteria being engulfed Macrophage destroying yeast
3m

8. Innate Immunity 2nd Line: Non – specific patrolling cells and proteins
1. Leukocytes: Phagocytic WBCs
attracted by chemical signals
released by damaged cells
ingest pathogens
digest in lysosomes
Neutrophils
most abundant WBC (~70%)
~ 3 day lifespan
Macrophages
“big eater”, long-lived

9. Innate Immunity 2nd Line: Non – specific patrolling cells and proteins
Natural Killer Cells (NK)
destroy virus- infected cells and cancer cells
recognize abnormal surface roteins on virus infected or cancerous cells
perforate cells
release perforin protein and
insert into membrane of target cell
forms pore allowing fluid to flow in and out of cell
cell ruptures (lysis)
NK cell
Perforin
Cell membrane
Virus infected cell

10. Innate Immunity 2nd Line: Non – specific patrolling cells and proteins
2. Complement System: anti-microbial proteins
~20 proteins circulating in blood plasma
attack bacterial & fungal cells
form a membrane attack complex
perforate target cell
apoptosis
cell lysis
complement proteins form cellular lesion
bacterial cell

11. Innate Immunity 2nd Line: Non – specific patrolling cells and proteins
Inflammatory Response- triggered by tissue damage
releases chemical signals: histamines & prostaglandins
capillaries dilate, become more permeable (leaky)
delivers macrophages, RBCs, platelets, clotting factors
increases temperature (inhibits bacterial growth,
stimulates phagocytosis, speeds up repair of tissues)
fever: if local response is ineffective, system wide response
- inhibits bacterial growth and stimulates phagocytois

12. Adaptive (Acquired) Immunity
Lymphatic System : involved in adaptive immunity
Body's drainage system
Composed of a network of vessels and small structures called lymph nodes
Lymph vessels convey excess fluid collected from all over the body back into the blood circulation.
These fluids are forced to percolate through the lymph nodes so that they can be filtered.
Harmful organisms are trapped and destroyed by the specialized white blood cells (lymphocytes) that are present in these nodes.
Lymphocytes are also added to the lymph that flows out of nodes and back to the bloodstream.

13. Adaptive Immunity Specific defense with memory lymphocytes B cells
Lymphatic System
Specific defense with memory
lymphocytes
B cells
T cells
antibodies
Responds to antigens
specific pathogens
specific toxins
abnormal body cells (cancer)

14. Adaptive Immunity: Lymphatic System

15. Adaptive Immunity Antigens: substance that elicits lymphocyte response
“self” antigens
no response from WBCs
“foreign” antigens
response from WBCs
pathogens: viruses, bacteria, protozoa, parasitic worms, fungi, toxins
non-pathogens: cancer cells, transplanted tissue, pollen
epitope (antigenic determinant)
- specific piece of the antigen
to which an antibody binds
amino acids long

16. cells learn to distinguish between
Adaptive Immunity Uses specialized lymphocytes (WBC) produced by stem cells in bone marrow
B cell lymphocytes
stay and mature in bone marrow
humoral response system “Shumors” = body fluids
plasma cells  antibodies
attack pathogens still
circulating in blood
and lymph
T cell lymphocytes
migrate to and mature in thymus gland (neck)
cellular mediated response system
attack invaded cells
(soldiers who search out and destroy the targeted invaders)
Maturation
cells learn to distinguish between
“self” and “ non-self”

17. Adaptive Immunity Proliferation of B and T Cells
In the body there are few lymphocytes with antigen receptors for any particular epitope
In the lymph nodes, an antigen is exposed to a steady stream of lymphocytes until a match is made
Binding of a mature lymphocyte to an antigen activates the lymphocyte
Once activated, a B or T cell undergoes multiple cell divisions
This proliferation of lymphocytes is called clonal selection
Two types of clones are produced:
effector cells- short lived
act immediately against the antigen
memory cells- long lived
give rise to effector cells if the same antigen is encountered again

18. Types of Adaptive Response
Humoral B Cells (antibodies)
Cell Mediated T Cells

19. Adaptive Immunity Humoral Response (Antibody production)
B Cells (lymphocytes)
Attack, learn & remember pathogens circulating in blood & lymph
Produce specific antibodies against
specific antigen
Types of B cells
plasma cells
immediate production of antibodies
rapid response, short term release
memory cells
continued circulation in body
long term immunity

20. Adaptive Immunity: Humoral Response
Antibodies: Immunoglobulins (Ig)
Made by B cells
Proteins that bind to a specific antigen
multi-chain
binding region matches molecular shape of antigen
epitope
each antibody is unique & specific

21. Adaptive: Humoral Response
Humoral = Antibodies B Cell Immune Response 10 – 17 days for full response

22. Adaptive Immunity: Humoral 1° vs 2° Response
Memory B cells allow a rapid, amplified response with future exposure to pathogen

23. Adaptive Immunity: Humoral How Antibodies Work

24. Adaptive Immunity: Humoral
Vaccinations
immune system exposed to harmless version of pathogen
stimulates B cell system to produce antibodies to pathogen
“active immunity”
rapid response on future exposure
creates immunity without getting disease
most successful against viruses
Passive Immunity
obtaining antibodies from another individual
maternal immunity
antibodies pass from mother to baby across placenta or in mother’s milk
critical role of breastfeeding in infant health
mother is creating antibodies against pathogens baby is being exposed to
short-term immunity

25. Adaptive Immunity: Cell Mediated Self vs Non Self
Major Histocompatability Complex (MHC)
method by which immune system recognizes “self”
Set of cell surface proteins essential for the acquired immune system to recognize foreign molecules
unique arrangements of proteins on surface of cells (cellular “fingerprint”-different for each person)
marks cells as “off limits” to immune system
MHC proteins
main function: to display foreign antigens on the cell surface for recognition
constantly carry bits of cellular material from cytosol to cell surface
give surface of cells unique label or “fingerprint”

26. Adaptive Immunity: Cell Mediated MHC I and MHC II
B and T cells bind to MHC molecule in the adaptive response
MHC I
presents antigens from infected cells & cancer cells
triggers cytotoxic T cells
MHC II
in phagocytic cells = antigen presenting cells
present antigens from digested pathogens
triggers helper T cells

27. Adaptive Immunity: Cell Mediated
T Cells (thymus cells)
activated if the attacker gets past B cells in blood and infects (hides in) cells
learn and remember pathogens hiding in infected cells
recognize “non self” antigens on cells
actively destroy infected cells, as well as to signal other immune cells to participate in the immune response
T cell attacking cancer cell

28. Adaptive Immunity: Cell Mediated
Killer T cell binds to infected cell
Types of T Cells
Cytotoxic T cells (CD8+ T cells)
killer cells
attack virus infected or cancer cells
contain protein (perforin)- punches holes in cells
cause cell to burst open
other proteins enter cell and trigger apoptosis
Helper T cells (CD4+ T cells)
alert rest of immune system
stumulated by interleukin-1 released by APC
activates other T cells
activates B cells  humoral response
HIV infects helper T cells and destroys them
infected cell
destroyed

29. Adaptive Immunity : Cell Mediated
Types of T Cells (cont.)
Memory T cell
long term immunity
stored in the lymph nodes and spleen
can provide lifetime protection against specific antigens
Natural Killer T (NKT) cells (not NK cells)
have properties of both T cells and natural killer cells
have T-cell receptors.
distinguish infected or cancerous cells from normal body cells
attack cells that do not contain body cell markers
Regulatory T cells (suppressor T cells)
suppress the response of B cells and other T cells to antigens
stops immune response once it is no longer needed
regulatory T cells defects can lead to autoimmune disease

30. Adaptive Immunity: Cell Mediated Antigen Presenting Cell (APC)
APC: cell with foreign antigens on cell membrane
(from MHC proteins that carry pieces to cell surface)
T cells detect foreign antigens and destroy them.
MHC I MHC II

31. Adaptive Immunity: Cell Mediated T Cell Response
once the T-cell receptor binds to the MHC molecule, the antigen-presenting cell secretes cell signaling proteins called cytokines.
cytokines signal the T cell to destroy the specific antigen, activating the T cell.
activated T cell multiplies and differentiates into helper T cells.
helper T cells initiate the production of cytotoxic T cells, B cells, macrophages, and other immune cells to terminate the antigen.

32. Adaptive Immunity: Cell Mediated Cytotoxic T Cells Attacking
cytotoxic T cell attacking cancer cell

33. Adaptive Immunity B Cells vs T Cells Review
humoral response (“in fluid”)
defend against extracellular pathogens (invaders in body fluids) by binding to antigens, making pathogens easier targets for phagocytes
T cells
cell-mediated response
defend against intracellular pathogens (invaders inside cells) & cancer cells by binding to & lysing infected cells or abnormal cells

34. Adaptive Immune Response Review

35. Immune System: HIV and AIDS
Human Immunodeficiency Virus
virus infects helper T cells
helper T cells don’t activate rest of immune system: killer T cells & B cells
also destroys helper T cells
AIDS: Acquired ImmunoDeficiency Syndrome
infections by opportunistic diseases
death usually from
“opportunistic” infections
pneumonia, cancers

36. Immune System Malfunctions
Auto-immune diseases
immune system attacks own molecules & cells
lupus
antibodies against many molecules released by normal breakdown of cells
rheumatoid arthritis
antibodies causing damage to cartilage & bone
diabetes
beta-islet cells of pancreas attacked & destroyed
multiple sclerosis
T cells attack myelin sheath of brain & spinal cord nerves
Allergies
over-reaction to environmental antigens
allergens - proteins on pollen, dust mites, in animal saliva
stimulates release of histamine

37. Key Attributes of Immune System
4 attributes that characterize the immune system as a whole:
1. specificity
antigen-antibody specificity
2. diversity
react to millions of antigens
3. memory
rapid 2° response
4. ability to distinguish self vs. non-self
maturation & training process to reduce auto-immune disease

38. Immune System Generalized Overview