CHAPTER 11 : IMMUNITY (5 hrs)

11.1 Immune Response (2½)

11.2 Development of Immunity (1½)

11.3 Immune Disorder ( 1 )

• Describe what is meant by immunity.• Describe the structure of antibody

and state the classes of antibodies.• Explain and compare humoral and cell

mediated immune response• Describe the roles of lymphoid organs

in immunity.• Describe various types of antigen and

antibody reactions.

11.1 : Immune Response (Objectives)

What is: Immunity ? Antigen ? Antibody ?

Structure of antibody

Classes of antibody

Immune response

Antigen & antibody reactions

11.1 : Immune Response

IMMUNITY

• Immunity = is a body defense against the many potentially dangerous viruses, bacteria and other pathogens.

• Involves the immune system.• Immune system = the body system

responsible for resisting disease.

Body Defense System

1st line of defense

2nd line of defense

3rd line of defense

Disease

Physical barrier that block the entry of antigen

Block the spread of antigen into the body

Specific defense system (immune system)

1st line of defense

Sweat, mucus, saliva, gastric acid, tears

Skin mucous membrane

2nd line of defense

Cut of the skin causes:- Damaged cells release chemical signal

Attract phagocytic WBC to the infected tissue

Stimulates blood clotting Ingest antigen by phagocytosis

Inflammatory response

Heat

Swelling

Pain

Redness

Defense System

Non-specific defense mechanismsSpecific defense

mechanisms (immune system)

1st line of defense 2nd line of defense

3rd line of defense

skin mucous membrane secretions of skin & mucous membrane

phagocytic leukocyte antimicrobial protein inflammatory response natural killer cell

Lymphocyte Antibodies

Ability of the body to recognize & protect itself against foreign substance that can cause disease

3rd line of defense (Immune System)

Immunity

Cell (eg: virus, bacteria) pathogen Soluble toxin, protein (eg: venom)

Foreign substance ?

CELL-MEDIATED CELL-MEDIATED IMMUNITYIMMUNITY

HUMORAL HUMORAL IMMUNITYIMMUNITY

SPECIFICSPECIFICIMMUNEIMMUNE

RESPONSERESPONSE

PHAGOCYTOSISPHAGOCYTOSIS

INFLAMMATIONINFLAMMATION FEVERFEVER

LEVELS OF DEFENSE AGAINST INFECTION

NONSPECIFICNONSPECIFICINTERNALINTERNALDEFENSESDEFENSES

If barriersIf barrierspenetrated:penetrated:

MUCOUS MUCOUS MEMBRANESMEMBRANES

(respiratory & digestive(respiratory & digestivetract) tract)

If nonspecificIf nonspecificinsufficient:insufficient:

NATURAL KILLER CELLSNATURAL KILLER CELLS

SKINSKIN(physical)(physical)

BARRIERSBARRIERS

Foreign substance that can provoke an immune response

Due to the presence of foreign molecules (usually protein on the membrane surface)

Intruder non-self

Antigen (Antibody generators)

Definition

Only a certain parts of antigen can provoke immune response

These parts ~ antigenic determinants (epitope)

Usually 1 antigen has many epitopes

Different epitope binds with different antibody

Antigenic determinants / Epitope

Blood Cell

Leukocyte Platelet

Granulocyte Agranulocyte

Neutrophil Eosinophil Basophil

Erythrocyte

LymphocyteMonocyte

Types of Blood Cells

Macrophage

Phagocytic

Phagocytic

differentiate

Produced in bone marrow

Lymphocytes

Remain & mature in Bone

Migrate & mature in Thymus

Lymphocyte

T cellB cell

Mature B & T cells migrate to lymphoid organ

Lymphoid Organ

Thymus

Spleen

Tonsil

Lymph Node

Bone Marrow

Lymphoid Organs

1

2

3

4

5

Small, round organ Found at intervals along lymphatic

capillaries Embedded in connective tissue

1. Lymph Nodes

Filter lymph Macrophage remove & destroy antigen Lymphocyte monitor presence of antigen &

activate immune system

Function

Bi-lobed structure (lower neck region) Size varies with age Childhood ~ larger, adolescent ~ stop

growing & reduce in size

2. Thymus

Secrete thymosin for T cell maturation

Function

In adult, red bone marrow ~ skull, spinal column, femur

Produce stem cells ~ differentiates into different types of blood cells

3. Bone Marrow

Site of blood cells synthesis Site of B cell maturation

Function

Largest lymphoid organ Curved-shaped (left side of stomach beneath

diaphragm) Consist of :-

White pulp - macrophage & lymphocyte Red pulp - RBC & macrophage

4. Spleen

Blood reservoir Remove & destroy antigen & worn-out blood

cells

Function

Simplest lymphoid organ Ring-like structure (around pharynx) Epithelium surfaces invaginate form crypts

5. Tonsils

Trap & remove pathogens that enter via nose & mouth

Protect respiratory system

Function

When activated, B cell differentiate to form plasma cell

That secrete antibody

B cell

A specific protein, immunoglobulin (Ig) that can bind to specific antigen

Produced by plasma cells Due to the presence of antigen

Found in plasma

Definition of antibody

Y-shaped

Has 4 polypeptide chains 2 heavy (H) chains 2 light (L) chains

Polypeptide chains are held together by disulfide bonds

Form antibody monomer

Antibody ~ Structure

Each chain has 2 regions Constant (C) region Variable (V) region – which binds to

antigen

Antibody ~ Structure

5 classes ~ based on the differences of C region

Classes of Antibody

Ig M1

2 Ig A

Ig D3

4 Ig G

5 Ig E

5-10% Largest, 5 monomer

(pentamer) Held together by a joining, J-

chain Most reactive 1st antibody produced during

first exposure to antigen

1. Ig M

Agglutinating antigen Complement fixation

Function

10-15% 2 monomers (dimer) Produced mainly by mucous membrane (secretory cells) Found in saliva, mucus, sweat, GI tract, tears, milk

(colostrum)

2. Ig A

Prevent attachment & entry of antigen to epithelial surfaces

Protect mucosal surface

Function

Less than 1% Monomer Mainly found on the surface of B-cells (antigen receptor)

3. Ig D

Function Act as antigen receptor on B cell

Help to stimulate B cell to differentiate to plasma cell & memory B cell

Help to initiate development of humoral immunity

Most abundant (75 - 85%) 1 monomer, smallest Can cross placenta Long lasting (mostly memory cells)

4. Ig G

Provide passive immunity (temporary protection) to fetus

Complement fixation

Function

0.002% (least produced) Monomer (slightly larger than IgG) Found on the surface of basophils & mast cell Release histamine when triggered by antigen

Promotes inflammation Responsible for allergic reaction

5. Ig E