1. GENERAL IMMUNOLOGY PHT 324
Dr. Rasheeda Hamid Abdalla
Assistant Professor

2. Immune System

3. OBJECTIVES Basic Terms in Immunology Innate immunity
Adaptive (acquired) immunity

4. Basic Terms in Immunology
Immunology: The study (science) which deal with the defence of our bodies against foreign substance which may cause infection.
Immunity: Resistance to infectious disease.
Immune system
The collection of cells and tissues that protects the body from infection

5. Basic Terms in Immunology
Immune response
The coordinated reactions of the cells of the immune system to a pathogen.
Antigen
Molecules that bind to antibodies or T cell receptors with High affinity.
Antigens may be in forms of:
Small molecules in the environment.
Bacterial and viral surface proteins.

6. Lymphocytes
Lymphocytes :cells found in the blood, lymphoid tissues and most organs of the body that express receptors for specific antigens and mediate immune responses.
The lymphocytes are B cells and T cells.
(B cell = B lymphocyte; T cell = T lymphocyte).

7. Lymphocytes
When B and T cells become activated, they divide and mature into effector cells that do the job of fighting the microbe.
Mature B cells are called plasma cells.
Mature T cells are called effector T cells.

8. Cytokines
Cytokines
Secreted proteins that work as mediators of immune and inflammatory reactions.
Provide a mechanism for cells of the immune system to coordinate a response.
Interleukin
Another term for a cytokine that acts on other leukocytes

9. The immune system The immune system
Collection of cells, tissues and molecules that designed to produce a coordinated response to the entrance of foreign substances or antigens into the body.
It is divided into two complementary arms:
Innate (native or natural) immune system.
Adaptive (acquired or specific) immune system.

10. Innate & Adaptive Immunity

11. Innate immunity
Refers to antigen-nonspecific defense mechanisms that a host uses immediately or within several hours after exposure to almost any antigen.
The immunity one is born with.
The initial response by the body to eliminate microbes and prevent infection

12. Innate immunity
Innate immunity does not recognize every possible antigen.
Instead, it is designed to recognize few structures present in many different microorganisms.
The structures recognized are called pathogen-associated molecular patterns.
Which include LPS, peptidoglycan, techoic acids, bacterial DNA, double-stranded RNA from viruses, and glucans from fungal cell walls.

13. Innate immunity
Most body defense cells have pattern-recognition receptors for the common pathogen-associated molecular patterns.
So there is an immediate response against the invading microorganism.
It is thought to recognize approximately 103 molecular patterns

14. Pattern-recognition receptors

15. Innate immunity The innate immune responses involve:
Phagocytic cells (neutrophils, monocytes, and macrophages).
Cells that release inflammatory mediators (basophils, mast cells, and eosinophils).
Natural killer cells (NK cells).
Molecules such as complement proteins and cytokines

16. Innate immunity It comprises 3 types of defensive barriers:
• Anatomical or physical (skin, mucous membranes).
• Physiological (temperature, pH, and chemicals such as lysozyme, complement, and some interferons).
• Phagocytic (monocytes, neutrophils, macrophages).

17. Adaptive (acquired) immunity
Refers to antigen-specific defense mechanisms that take several days to become protective.
Designed to react with and remove specific antigen.
This is the immunity which one develops throughout his life.

18. An antigen
An antigen
defined as a substance that reacts/binds with antibody molecules and antigen receptors on lymphocytes.
The portions or fragments of an antigen that react with antibodies and lymphocyte receptors are called Epitopes.

19. An antigen
The body recognizes an antigen as foreign when epitopes of that antigen bind to B-lymphocytes and T-lymphocytes by means of epitope-specific receptor molecules having a shape complementary to that of the epitope.

21. B-cell & T-cell receptors
The epitope receptor on the surface of B-lymphocyte is called B-cell receptor.
The receptor on T-lymphocyte is called T-cell receptor (TCR).
It is thought that the human body has the genetic ability to recognize different epitopes

22. T cells

23. B cells

24. B cells

25. Adaptive (acquired) immunity
Adaptive immunity improves upon repeated exposure to a given infection and involves:
Antigen-presenting cells (APCs) such as macrophages and dendritic cells.
The activation of antigen-specific B-lymphocytes and T-lymphocytes.
The production of antibody molecules, cytotoxic T-lymphocytes (CTLs), activated macrophages and NK cells, and cytokines.

26. Adaptive (acquired) immunity
There are two branches of adaptive immune responses:
1. Humoral immunity: involves production of antibody molecules in response to an antigen and is mediated by B-lymphocytes.
2. Cell-mediated immunity: involves the production of cytotoxic T-lymphocytes, activated macrophages, activated NK cells, and cytokines in response to an antigen and is mediated by T-lymphocytes.

28. Thanks

29. https://www.youtube.com/watch?v=sYjtMP67vyk (INNATE IMMUNITY)
(ADAPTIVE IMMUNITY)