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Presentation on theme: "IMMUNITY."— Presentation transcript:


2 What is Immunity? Ability of the body to protect itself from viruses, bacteria, and other disease causing agents The word immunity comes from the Latin word immunis meaning exempt

3 IMMUNE SYSTEM SPECIFIC response to foreign substances
Substances that evoke the response are called ANTIGENS Immune response produces proteins that are specific to the antigen, these are ANTIBODIES Specific white blood cells called LYMPHOCYTES are produced

4 Types of Acquired Immunity
Naturally acquired immunity Artificially acquired immunity

5 Naturally acquired immunity
ACTIVE – exposure to antigen naturally in the course of daily life This is the type of immunity from having a disease PASSIVE – maternal antibodies transferred via the placenta or mother’s milk Temporary immunity for the newborn

6 Artificially acquired immunity
ACTIVE – vaccination Receive antigen via injection of vaccine Produce antibodies against the injected antigen PASSIVE – preformed antibodies Receive preformed antibodies from immune person or animal Antiserum Temporary protection

7 Duality of Immune System
Humoral immunity Production of antibodies B cell activation Active against bacteria, toxins, and viruses that are circulating in body fluids Cell-mediated immunity Activation of T cells Active bacteria and viruses that are inside host cells

8 What are Antigens? Things that are foreign to our body
Usually proteins or large polysaccharides Antigenic determinants are often parts of the invading microbe Antibodies react with specific regions of the antigen called EPITOPES

9 Antigenic determinants

10 What are Antibodies? Antibodies are proteins
React with only ONE specific antigen Neutralize or destroy the antigen Each antibody has specific antigen binding sites

11 Antibody structure Consists of 4 chains 2 light and 2 heavy chains
Variable regions of antibody bind specific antigen

12 Antibody structure

13 Antibody variable regions (antigen binding sites)

14 Classes of Antibodies (Immunoglobulins)

15 IgG Single unit monomer antibody
80% of all antibodies are of this class Crosses the placental barrier to protect fetus Protects against CIRCULATING bacteria, viruses, and toxins

16 IgM 5 monomer antibody 5-10% of antibody in serum
First class of antibodies formed to antigen Reacts with human ABO blood groups Clumps the antigen

17 IgA 2 unit monomer antibody 10-15% of antibodies in serum
Abundant in mucous membranes, tears, saliva, and breast milk Prevents pathogen attachment to mucosal surfaces

18 IgD Single unit monomer antibody 0.2% of serum antibody
Found in blood and lymph Antigen receptor on B cells

19 IgE Single unit monomer antibody 0.002% of antibodies in serum
Binds to mast cells and basophils Allergic reactions


21 B cells Develop in the bone marrow Migrate to lymph nodes and spleen
Recognize antigen by cell surface receptors Activated B cells divide to form plasma cells which secrete antibody

22 Clonal Selection B cell is sensitized by specific antigen
Divides to form many more identical cells (clones) The clones differentiate into plasma cells that secrete antibody formed against the antigen Some cells become memory cells to provide protection for years to come

23 Clonal Selection

24 Results of Antigen-Antibody Binding
1. Agglutination 2. Opsonization 3. Neutralization 4. Complement activation 5. Inflammation

25 Results of Antigen-Antibody Binding

26 Monoclonal Antibody Production

27 Uses of Monoclonal Antibodies
Diagnostic kits Pregnancy testing Suppression of tissue rejection in transplants Disease treatment

28 Primary and Secondary Immune Response
Primary response to antigen is by IgM antibodies IgG antibody production begins several days later Second exposure to antigen results in IgG production immediately and in large quantities Anamnestic (memory) response


30 Memory response

31 Cell-mediated Immunity
Based on the activity of T cells T cells are a class of lymphocytes that are produced in the bone marrow but mature in the thymus gland Distributed in the various lymphatic organs Effective against intracellular antigens

32 What are Cytokines and Interleukins?
Cytokines are the chemical messengers of the immune system Interleukins are the cytokines that serve as communicators between white blood cells There are now at least 26 different interleukins (IL) many of which have important functions in the immune system

33 T cells T cells are the key cellular component of immunity
There are 4 main types of T cells T Helper cells* Cytotoxic T cells* Delayed hypersensitivity T cells Suppressor T cells

34 CD – no not compact discs (Cluster of differentiation)
T cells carry surface receptors called CD’s that are used to differentiate between the various types of T cells T helper cells are classified as CD4 cells by their receptor Cytotoxic T cells are CD8 cells

35 T Helper cells Key cell that activates cell-mediated immunity and links humoral (antibody) immunity to cell-mediated immunity The T helper cell is attacked and destroyed by the AIDS virus leading to immune system failure

36 T - helper cells and HIV Time course

37 Helper cell activation
Antigen is presented to the helper cell by another cell called an APC cell APC cell and T helper cell bind APC cell secretes IL-1, T helper cell is now activated! IL-1 simulates the T helper cell to secrete IL-2 IL-2 secretion stimulates the activated T(H) cell to form clones of itself and also to stimulate other cells such as B cells to make antibody, and T(C) to attack infected cells

38 T helper cell activation


40 Cytotoxic T cells Once activated by the T(H) cell the T(C) seek out and destroy infected cells in the body The T(C) bind with infected cells and release PERFORIN that causes the infected cells to burst (lyse)

41 Cytotoxic T cell activity

42 How the Cytotoxic T cells works

43 T cell/B cell interaction

44 T cell/B cell interaction

45 Immune system summary

46 Summary of cell-mediated immunity
APC’s stimulate the T(H) cell The T(H) cell is central to both humoral and cell-mediated immunity T(H) cells stimulate B cells to make antibody and cytotoxic T cells to destroy infected cells Without T(H) both aspects of immunity will fail and so will you!

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