1. College Board 2.D.3 – Biological Systems Are Affected By Disruptions to Their Dynamic Homeostasis
Disruptions at the molecular level and cellular levels affect the health of the organism
Dehydration
Immunological responses to pathogens, toxins, and allergens

2. 2.D.4 - Plants and Animals Have a Variety of Chemical Defenses Against Infections That Affect Dynamic Homeostasis
Plants, invertebrates and vertebrates have multiple, nonspecific immune responses
Invertebrates lack pathogen-specific defense responses
Plant defenses include molecular recognition with systemic responses, infection triggers chemical responses that destroy infected and adjacent cells, localizing the effects.

3. Mammals use specific immune response triggered by natural or artificial agents
Two types of response: humoral and cell-mediated
Cell-mediated – cytotoxic T cells target pathogens when antigens are displayed on the outside of cells
Humoral – B cells produce antibodies against specific antigens
Antigens are recognized by antibodies
Antibodies are proteins produced by B cells and are specific
A second exposure to the antigen produces a faster and enhanced response

4. Acquired immunity
Antibody
Antigen
APC
B cell
CD4
CD8
Clonal selection
Cytokines
Histamine
Inflammatory response
Innate immunity
Interferons
Lymphocyte
MHC I
MHC II
Non specific response
Specific response
T cell

5. Innate vs Acquired Immunity
Defend against ‘non-self’
Get rid of abnormal cells
Two kinds of defense
Innate immunity – nonspecific
Acquired immunity - specific
Specific
Nonspecific – effective at birth
Abnormal signals from ‘self’ cells

6. Nonspecific Immunity - External
Skin – low pH, oily
Lysozyme – breaks down bacterial cell walls
Gastric juice
Symbiotic bacteria in gut and on skin

7. NonSpecific - Chemicals
Interferons – secreted by virus-invaded cells to warn other cells
Inflammatory response
Histamine
Vasodilation (swelling, heat and redness)
Attracts phagocytes

8. Damage causes release of histamine
Capillaries dilate: clotting factors, WBC’s arrive
Interleukins + histamine attract leukocytes
WBC’s eat microbes. More histamine (+ feedback)

9. Specific Immunity Cell receptors for antigens
Distinguish ‘Self’ from ‘nonself’

10. Macrophages
Antigen-presenting cell (APC) – macrophage that has engulfed a microbe and displays pieces on its surface

11. MHC
Major Histocompatibility Complex – molecules encoded by a family of genes
‘Self’ recognition
Prevents your body from attacking itself
Glycoproteins
Diversity –
20 different genes (polygenic)
50 different alleles – (multi-allelic)
MHC is a unique ‘fingerprint’ of you

12. MHC/antigen combo is recognized by a T cell
‘Regular’
A fragment of (antigen) inside an invaded cell attaches to an MHC molecule and is transported to the cell surface
MHC/antigen combo is recognized by a T cell

13. Infected body cells use MHC to display foreign antigens
Antigen inside an Antigen-presenting cell attaches to an MHC molecule and is transported to the cell surface.
MHC – antigen combo is recognized by a T cell

14. Acquired Immunity: Specificity
Antigen – molecule that elicits an immune response
Viruses, pollen, parasites, venom, transplants
Unique molecular (3-d) shape
Wide variety of lymphocyte’s in your blood in order to recognize all the possible antigens (genetic variation)
Antibody – bind to antigens
Immunoglobulin – protein (specific 3d shape for each antigen)
Inactivate antigens by binding to the epitope
Also bind to surface antigens of ‘non-self’ cells

15. Acquired Immunity
Lymphocytes – produced in bone marrow, hang out in lymph
B and T cells
Respond to specific ‘invaders’ (transplants, cancer)
Have 100,000 antigen-specific receptors in their membranes
Antigen receptors (‘membrane antibodies’, ‘membrane immunoglobulins’) - bind to specific antigens

16. Lymphocytes – Leukocytes Produced in Bone Marrow
B cells:
Mature in bone marrow
Respond to antigens
Clone into Plasma cells or Memory cells
T Cells:
Mature in thymus
Respond to funky self or non-self antigens
Clone into cytotoxic T’s or Helper T’s

17. T Cell Receptors and MHC
T cell antigen receptors recognize specific pieces of antigens bound to MHC molecules
T cells detect the antigen fragment in two ways:
An ‘infected’ body cell
An APC

18. Humoral and Cell-mediated Immunity
Lymphocytes only respond to specific antigens
Clonal selection – when the lymphocyte attaches to an antigen the lymphocyte clones itself:
One clone - effector cells
Short-lived cells that fight that antigen
One clone - memory cells
Long-lived cells with receptors for that antigen

19. Two Branches of Acquired Immunity
Cell-mediated Response:
Activate and clone cytotoxic T cells
T’s differentiate into:
Cytotoxic T’s
Memory T’s
Attack targeted specific body cells with an MHC-antigen complex
Humoral Response:
Activate and clone B cells
B’s differentiate into:
Plasma cells
Memory cells
Antibodies are secreted and attack antigens in body fluids

21. Clonal Selection of Lymphocytes
Primary (specific) immune response
Clonal selection – an antigen binds to a B or T cell receptor and activates it to clone and differentiate
Secondary response – memory cell clones
Faster response (2-7 days)
Provides resistance to infection
Vaccines

22. Helper T’s Both humoral and cell-mediated
Helper T’s are activated by APCs, or infected cells
MHC

23. Cytotoxic T Cells
Cytotoxic T becomes a killer (effector) cell when it binds to an infected body cell
Secretes perforin
Body cell releases antigens into humor and B cells attack released antigens
Also attack cancer – (cancer cells have ‘non-self’ molecules)

24. Cytotoxic T cell binds to a class I MHC–antigen complex on a target cell (TCR + CD8). TCR/MHC, + cytokines from helper T cells, activates cytotoxic T’s
Activated T cell releases perforin, proteolytic enzymes (granzymes); enter the cell by endocytosis
Granzymes initiate apoptosis; (‘cell suicide’). Cytotoxic T’s then attack other target cells

25. B Cells: Humoral Response
Helper T’s activate B cells
B cells clone into plasma cells and memory cells
Plasma cells (effectors) secrete antibodies into fluids (humor)
Memory cells enable rapid response to subsequent infections

26. B cell w/same antigens display them to helper T
B cell w/same antigens display them to helper T. TCR + CD4 + cytokines stimulates B to clone

27. + cytokines
Primary immune response; Plasma cells secrete antibodies (2000/sec); short-lived (4-5 days)
Effectors

28. Types of Immunity Active: Passive
Immunity develops from exposure to a pathogen (memory)
Naturally
Artificially – vaccination
Pathogens change
Passive
Passed via placenta or mother’s milk
Lasts weeks – months
Can be via immunization
Emergency – short term (rabies)

29. Autoimmune Diseases Immune system loses ‘self-tolerance’
Systemic lupus erythematosus (lupus)
Rash, fever, kidney problems, arthritis
Multiple sclerosis
T cells attack myelin sheath of CNS
Senses weakened, muscular control, paralysis

30. Auto Immune Disorders Insulin-dependent diabetes mellitus
T’s attack Beta cells of pancreas (insulin)
Rheumatoid arthritis
Damage and painful inflammation of the cartilage and bone of joints
Acquired immunodeficiency Syndrome (AIDS)
Loss of Helper T’s (HIV)
Patients die from opportunistic infections and cancers
Kaposi’s sarcoma
Pneumonia (Pneumocystis carinii)

31. Non-Specific; Innate Immunity
Response is always the same
Physical barriers – skin, mucous, tears
Inflammatory response
Histamine – mast cells
Dilation, fever activates other players
Chemicals – interferon
Phagocytic cells – macrophages
NK cells – abnormal cells (cancer, transplants)