1. Part II Biology 2122 Chapter 21
Immunity
Part II
Biology 2122
Chapter 21

2. Adaptive or Specific Immune Response
Introduction
Specific against a single pathogen
Systemic
Memory capabilities
1. Humoral Immunity
B-Cell Lymphocytes produce antibodies
Antibodies bind to a specific antigen and immobilize them
2. Cell-mediated Immunity
Lymphocytes defend the body
Centers on Cellular targets

3. Antigens ‘Antigens’ - large complex natural and synthetic molecules
foreign to the body.
They provoke an immune response.
Antibodies or lymphocytes
‘specific’ for an antigen bind to antigens at the part called ‘antigenic determinant’ binding sites.
One antigen may contain several binding sites
several antibodies may attach to them and provoke the immune response.
Antigens

4. Immunogenicity and Reactivity
Complete Antigens have both of these properties.
Immunogenicity is the ability of a antigen to cause the production of lymphocytes and antibodies
They are reactive
Have the ability to react with the activated lymphocytes and antibodies released by immunogenic reactions.
Complete Antigens
Microbes, nucleic acids, lipids, poylsaccharides, proteins (strongest), pollen grains.

5. Incomplete antigens (haptens) Small peptides, hormones, etc.
They are not immunogenic
but if they bond with the body’s proteins, can cause an attack by the immune response that is harmful
Examples are poison ivy, animal dander, cosmetics, products used in the house hold
Antigen Animations

6. Antibody Structure ‘Immunoglobulins’
Composed of heavy chains and light chains.
The variable region changes depending on the antigen it will react with.
These combine with the antigen-binding sites
C or constant region - dictates the cells and chemicals it can bind to.
Immunoglobulin Classes
1. IgM – on B-surface cell (antigen receptor)
2. IgA – plasma, in saliva, sweat, etc.
3. IgD – B-cell; antigen receptor
4. IgG – most abundant; protects against bacteria, viruses, toxins
5. IgE – plasma cells in skin, GI mucosae, respiratory tract

7. Monoclonal Antibodies
Antigen-Antibody Testing Complexes
Pregnancy Testing

8. MHC Proteins – Recognizing ‘Self’
Your cells – surface proteins
MHC proteins (glycoproteins)
‘Self-Antigens’
Classes of MHC Proteins
1. MHC I – all body cells
2. MHC II – only on immune response cells
Role in adaptive defense system

9. Cells of the Adaptive Immune System
Immature lymphocytes
produced in the bone marrow - will mature into a B or T lymphocytes
Each become immunocompetent in different locations
T-lymphocytes in the thymus
B-lymphocytes in the bone marrow
Positive selections
refers to the process of selecting T cells whose receptors that can recognize self-MHC molecules.
T-cells then proceed to negative selection in the thymus
If a T-cell binds too tightly to a self-MHC are eliminated
The cells that survive has developed self-tolerance (unresponsiveness to self-antigens)

10. Lymphocyte mobilization

11. T CELL SELECTION – Positive and Negative Selection

12. Cells of the Adaptive Immune System
When these cells become immunocompetent
display receptors on their surface
It is committed to one and only one antigen!
This process occurs prior to encountering an antigen.
These receptors are determined by our genes.
After they become immunocompetent
migrate to Lymph nodes, spleen, lymph organs
The final maturation of the T or B cells
when they encounter and lock onto an antigen.

13. What are Antigen-Presenting Cells?
Dendritic cells in CT, Langerhans’ cells of the epidermis, macrophages and activated B-cells.
Ingest antigens - present parts of the antigen on their surface.
Encountered by T-cells - antigen presentation
T cells circulate throughout the body.
Role of T-Cells
APCs are found in great concentrations in:
Lymph node Paracortical area
B-cells - germinal centers of the spleen.
Macrophages in medullary sinus of spleen (fixed)
APC Animation

14. Humoral Immune Response
Naïve B-lymphocytes (immunocompetent)
bind to antigens and then undergo a process called clonal selection.
B-cell clone division
produces different types of B-cells
B-cells attach to antigens in the ‘extracellular environment’
Most become plasma cells which secrete antibodies.
Others differentiate into memory cells
mount an immediate response on future encounters with the antigen.

15. Humoral Response- Clonal Selection of B-Cells

16. Humoral Response
Humoral Animationhttp://bcs.whfreeman.com/thelifewire/content/chp18/ html

17. Primary immune Response first exposure - 3-6 day lag
Memory
Primary immune Response
first exposure day lag
B cells - go through clonal selection
differentiate into plasma cells
antibody levels peak in 10 days
Secondary Immune Response
Second exposure; faster and more effective
Plasma cells produced hours after antigen exposure
2-3 days antibody concentration increases and remains high for several weeks
antibodies bond more efficiently with antigens
may remain for life

18. Humoral Responses

19. Active and Passive Humoral Immunity
1. Active Humoral Immunity
B cells encounter antigens - produce antibodies
(a) naturally acquired
(b) artificially acquired
Vaccine Animation
2. Passive Humoral Immunity
Donor’s antibodies injected into the bloodstream of another person
Crossing of mother’s antibodies to placenta (naturally acquired)
Short-lived; no memory is established
Artificially acquired by injection of immune serum

21. Action of Antibodies
1. Antibodies work with the complement protein system.

22. Cell-Mediated Immune Response
Antibodies provide very little protection against antigens that invade body cells.
Ineffective (viruses, other intercellular pathogens)
Cell-Mediated Immune Response
T-Cells (TH – CD4); (TC – CD8); (memory, regulatory T-Cells)
T-Cells only recognize “processed” or presented fragments of antigens.
Cell-Mediated Immune Response Animation

23. T-Cell Development CD4 and CD8 T-Cells mature in the Thymus Gland.
Activated by ‘APCs’.
Class-I MHC proteins: displayed by most all body cells; recognized by CD8 cells. Becomes activated into TC cells and Suppressor T- Cells
This process is endogenous (endogenous antigen)
Class II MHC: Immune cells like macrophages present to CD4 cells
Exogenous process
Helper T-Cells
MHC Antipresenting Cell Animations

24. Endogenous
Process
Antigen Recognition and MHC restriction
Exogenous
Process

25. Double Recognition and Activation
Clonal selection
T-cells must accomplish double recognition
Figure shows a CD8 cell becoming activated by Class I MHC protein (antigen fragment on its surface)
Cloning process forms TC Cells

26. T-Cell must bind to other surface receptors on APC
Activation of T-Cells
1. Antigen Binding
2. Co-stimulation occurs after antigen APC or body cell encounters the T-cell
Step before cloning
T-Cell must bind to other surface receptors on APC
B7 protein of dendritic cells
IL – I and II (cytokines)
Released by T-cells or APCs prompt cloning to start
Other Cytokines (Table 21.4)

27. Specific Roles of T Cells
1. Helper T cells
2. Cytotoxic T Cells (killer T cells)
3. Suppressor T Cells
4. Gamma Delta T Cells
T Cell Animationshttp://highered.mcgraw-hill.com/sites/ /student_view0
5. Regulatory T-Cells

28. Immune Response to Specific Pathogens
Primary Immune Response
Immune Response
Immune Response to Specific Pathogens

29. Imbalances and Diseases
1. Severe Combined Immunodeficiency
2. AIDS
HIV
3. Autoimmune Disorders MS
Graves disease
Lupus
Rheumatoid Arthritis