1. The immune system and the oral cavity
2nd part
Adaptive or acquired immunity
Done by Dr. Zubaida Najat

2. Adaptive Immune System – Introduction
Adaptive: responds to specific foreign substances
Innate & adaptive mechanisms work together

3. Types of Acquired Immunity
Figure 21.11

4. Types of Acquired Immunity
1- Passive acquired immunity includes
a- Naturally passive acquired immunity
antibodies are pass through placenta of fetus
b- Artificially passive acquired immunity:The injection of alredy prepared antibodies such as gamma globulin

5. 2- Active immunity
a- Natural active acquired immunity
Following clinical or subclinical infections
b-Artificial active acquired immunity:-
[[[[[Following vaccination with live or killed infectious agents or their products

6. Adaptive Immune System: Cells
Lymphocytes
T-cells
B-cells
Antigen Presenting Cells (APCs)

7. Acquired immunity is triggered in vertebrates when a pathogen evades the innate immune system and
(1) generates a threshold level of antigen and
(2) generates "stranger" or "danger" signals activating dendritic cells
The major functions of the acquired immune system include:
Recognition of specific "non-self" antigens in the presence of "self", during the process of antigen presentation.
Generation of responses that are tailored to maximally eliminate specific pathogens or pathogen-infected cells systemic action .
Development of immunological memory, in which pathogens are "remembered" through memory B cells and memory T cells.

8. Antibody Targets & Functions
Immune complex formation = antigen-antibody binding.
All the following events are initiated by antigen-antibody binding.
Complement fixation:
Neutralization:
Agglutination:
Precipitation:
Inflammation & phagocytosis prompted by debris

9. Adaptive, Humoral Immunity
Antigen – “any substance when introduced into the body stimulates the production of an antibody”
Bacteria, fungus, parasite
Viral particles
Other foreign material
Pathogen – an Antigen which causes disease

10. Adaptive, Humoral Immunity
Complete antigens (proteins, nucleic acids, lipids, polysaccharides):
Immunogenicity: the ability to stimulate specific lymphocytes & specific antibodies
Reactivity: the ability to react with activated lymphocytes & antibodies
Hapten (an incomplete antigen): a smaller molecule that is not immunogenic until attached to proteins

11. Adaptive, Humoral Immunity
Antigenic determinants: sites on an antigenic molecule that are immunogenic
Epitope
Major Histocompatibility Complex (MHC): cell surface glycoproteins associated with self recognition

12. Humoral Immunity Active humoral immunity: Passive humoral immunity:
B-cells encounter & respond to antigen to produce an antibody
Passive humoral immunity:
Introduced “non-native” antibody

13. Antibodies
Antibody – “a Y-shaped protein, found on the surface of B-Cells or free in the blood, that neutralize antigen by binding specifically to it”
Also known as an Immunoglobulin
Constant (C) region defines antibody class
determines chemical & cellular interactions
determines how class functions to eliminate antigens

14. Humoral Mediated Immunity
T-Cell
Cytokines
Plasma Cell
B-Cell

15. Antibodies Immunoglobulins & gamma globulins Structure variable
hypervariable
constant
Figure 21.13a

16. Antibody Classes
Antibody Classes: IgM, IgG, IgA, IgD, IgE (Ig = immunoglobulin)

17. Antibody Classes IgM: occurs as a monomer & a pentamer
Occurs on the B-cell surface (Monomer).
The Ig of early primary plasma cell response, circulating antibody; a potent agglutinator. Complement binding (Pentamer).

18. Antibody Classes IgE: the Ig associated with allergies.
Stem binds to mast cells & basophils.
Receptor binding results in histamine release & inflammation.
Found mostly in mucosa of respiratory & GI tract (Monomer).

19. Antibody Classes
IgG: the most abundant circulating Ig. The dominant circulating Ig of the primary & the secondary response. Crosses the placenta. Complement binding (Monomer).
IgA: the Ig of secretions. Helps prevent antigen penetration of membranes (Dimer).
IgD: the Ig of B-cell activation. Found on B-cell surface (Monomer).

21. Adaptive Immune System: Cells
Immunocompetence: as T- or B-cells mature they become immunocompetent, they display receptors on their cell membrane for a specific antigen.
All of the receptors on one cell are identical; immunity depends upon genetic coding for appropriate receptors.

22. Immunocompetent B or T cells
Key:
= Site of lymphocyte origin
Red bone marrow
= Site of development of immunocompetence as B or T cells; primary lymphoid organs
= Site of antigen challenge & final differentiation to activated B & T cells
Immature lymphocytes
Circulation in blood 1 1 1
Lymphocytes destined to become T cells migrate to the thymus & develop immunocompetence there. B cells develop immunocompetence in red bone marrow.
Thymus
Bone marrow 2
After leaving the thymus or bone marrow as naive immunocompetent cells, lymphocytes “seed” the lymph nodes, spleen, & other lymphoid tissues where the antigen challenge occurs.
Immunocompetent, but still naive, lymphocyte migrates via blood 2 2
Lymph nodes, spleen, & other lymphoid tissues 3
Mature (antigen-activated) immunocompetent lymphocytes circulate continuously in the bloodstream & lymph & throughout the lymphoid organs of the body. 3 3
Activated immunocompetent B & T cells recirculate in blood & lymph
Figure 21.8

23. Adaptive Immune System: Cells
Antigen Presenting Cells (APCs) APCs ingest foreign material, then present antigenic fragments on their cell surface where they are recognized by T-cells APCs: Macrophages & B lymphocytes Interactions between APCs & lymphocytes & lymphocyte-lymphocyte interactions are critical to immune response

24. Adaptive, Humoral response
Humoral response (clonal selection)

25. Figure 21.14

26. Cellular Immunity Tcell CD4& CD8

27. Adaptive Immune System: Cells
Lymphocytes: initially uncommitted
T-cells: are sorted in the Thymus
Positive selection: recognize MHC survive
Negative selection: react against to self-antigens on MHC killed
2% of initial T-cell precursors
T-cells manage the immune response

28. Cell Mediated Immune Response
T-cell activation: involves recognition of PM surface antigens only
Antigen is combined with MHC & displayed on PM
T-cell receptors: bind to the MHC & are stimulated by the associated antigen
The addition of a co-stimulator (cytokines, interleukins, etc) prompts the T-cell to form a clone

29. Helper T Cells (TH)
Figure 21.17a

30. Professional APCs CD4+ Th1-Cells
IL-2
Protein
IFN-gamma
Macrophage
TNF-alpha

31. Cell Mediated: MHC MHC occurs as two classes
MHC I on virtually all tissue cells
MHC II only on PM some immune system cells

32. Cell Mediated: MHC display properties
MHC I on virtually all tissue cells
Display only proteins produced inside the cell
Endogenous antigens = foreign proteins produced by the cell (viral / cancer)
Stimulate the CD8* cell population
form cytotoxic T-cells (Killer T, TC)
*formerly T8 cells

33. Cell Mediated: MHC display properties
Figure 21.16b
MHC II found only on PM of B-cells, some T-cells & APCs
Display proteins derived from a phagocytized target
Exogenous antigen: foreign protein from outside the cell – presented to PM surface
Stimulates the CD4* cell population
form Helper T-cells (TH)

34. Cell Mediated: T-cell roles
Helper T-cells (TH) stimulate B-cells & other T-cells to proliferate
Figure 21.18

35. Cell Mediated: T-cell roles
Activated TH cells interact with B-cells displaying antigen & produce cytokines that prompt the B-cell to mature & form antibody

36. Cell Mediated: T-cell roles
TH cells also produce cytokines that promote TC cells
TH cells recruit other WBCs & amplify innate defenses (inflammatory)
Subpopulations of TH cells specialize in specific sets of activations

37. Cell Mediated: T-cell roles
Cytotoxic T-cells (TC, Killer T): directly attack & kill cells with specific antigen
Activated TC cells are co-stimulated by TH cells

38. Cell Mediated: T-cell roles
TC mechanism (Cytotoxic T-cells, Killer T)
TC binds to cell & releases perforin & granzymes
In the presence of Ca2+ perforin forms pores in target cell PM
Granzymes enter through pores & degrade cellular contents
TC then detaches & moves on
Macrophages clean up

39. Cell Mediated: T-cell roles
Other T-cells
*Regulatory T-cells (TReg): release inhibitory cytokines that suppress B-cell & T-cell activity
Help to prevent autoimmune events
*formerly Suppressor T (TS)
Gamma Delta T-cells (Tgd): live in the intestine. Function in surveillance & are triggered much like NK cells

40. Cellular Mediated Immunity

41. Summary of the Primary Immune Response
Figure 21.19