CHAPTER 11 : IMMUNITY (5 hrs)

11.1 Immune Response (2½)

11.2 Development of Immunity (1½)

11.3 Immune Disorder ( 1 )

• Describe and explain the primary and secondary immune responses to antigen.

• Explain the concept of self and non-self recognition and its application in organ transplant, grafting and blood transfusion.

11.2 : Development of Immunity (Objectives)

Active

Natural Artificial

Passive

Types of Immunity

Immunity

Natural Artificial

Antibody from: pregnant mom to

fetus Nursing mother to

infant

Antibody from Injected antibody from

animal / people to another people

Exposed naturally to antigen

By immunization or vaccination

Passive immunity Obtain antibody from outside Effect : immediate but short-lived

Active immunity Produce own antibody due to entrance of

antigen Effect : longer time but long-lived Has immunological memory

Vaccination

For active immunity, it develops within 2 stages:-

Development of Immunity

Primary immune response

Secondary immune response

Immunity

1st exposure to the antigen

2nd exposure to the same antigen

Primary & Secondary Immune Responses

Has a longer lag period (where no antibody is produced)

Due to the time needed for the specific B cell to:

Primary Immune Response

Become activated

Proliferate (producing clone)

1

2

Differentiate (plasma cell & memory cell)

3

Plasma cell secrete antibody (mainly Ig M) Amount of antibody is relatively low After a short time, amount of antibody decrease

Has a very short lag period (due to the presence of memory B cells ~ immunological memory)

Production of antibody is :-

Secondary Immune Response

faster

higher amount

1

2

more prolonged (remain longer)

3

Antibody level tends to remain high for longer period

Plasma cell secrete antibody (mainly Ig G)

Obtained by vaccination / immunization

Obtained by injecting small amount of vaccine into the body

Which trigger immune response Effect :- produce antibody against injected

antigen Vaccine is inactivated toxins or weakened /

dead pathogen Which trigger immune system to produce

antibody, but can no longer cause disease

Artificial Active Immunity

Vaccination

Vaccination

• BCG (tuberculosis) • After birth / 13 yrs

• Hepatitis B • After birth / 1 mth / 6 mths

• Triple Antigen (DPT)-Diphteria (sore throat)-Pertusis (whooping cough)-Tetanus

• 3 / 4 / 5 mths

• Polio • 3 / 4 / 5 mths

• MMR-Measles-Mumps-Rubella

• 4 yrs

a.k.a Human Leucocyte Antigen (HLA) Is known as self antigen Each person has a unique MHC (except identical twins) That differentiate our own cells with other person

MHC

MHC

Class I Class II

found on all cells (except RBC)

found on cells involved in immune response (macrophage, B cell)

Our immune system can recognize foreign cells & own body cells

Due to presence of MHC Self antigen does not provoke immune

response Non-self antigen trigger immune response

Non-self includes:- Antigen Cells from other individuals / organisms

Self & Non-self Concept

Concept of Self & Non-self Recognition

Antigen receptors are tested for self-reactivity

Lymphocytes carrying receptors that can bind to molecules already present in the body are inactivated or destroyed by apoptosis

Only lymphocytes that recognize foreign molecules continue to develop

Helps to recognize self from non-self (self-tolerance)

Failure to recognise self antigen leads to autoimmune diseases

Self & Non-self Concept

Skin Grafting

Blood transfusion

Organ transplant

1

2

3

Transfer of blood from 1 person to another

Blood group must be determined before it can be transferred

By using ABO blood group system

Blood group can be determined by antigen found on red blood cell (RBC) membrane

Blood Transfusion

Blood Transfusion

Antibody B

Has antigen A

Blood A Blood B Blood AB

Blood O

Has antigen B

Has antigen A & B No antigen

Antibody A

No antibody

Antibody A & B

If the antigen & complementary antibody is present in the blood, agglutination occurs

Blood O universal donor Because it has no antigen on the surface

does not trigger immune response

Blood AB universal recipient Because it has no antibody (for blood)

does not cause agglutination

Blood Transfusion

Blood Transfusion

Why is it easier to transfer blood compared to transfer

organ ??

RECALL that RBC doesn’t have MHC Type of antigen present

A & B

Blood Transfusion

Skin Grafting

Replacement of damaged tissue / organs with a healthy one

3 kinds of transplant

Skin Grafting & Organ Transplant

Autografts

Isografts

1

2

Allografts3

Tissue (skin) grafted from 1 area to another on the same person

Same MHC no rejection

1. Autografts

A graft between genetically identical individuals

Identical twins Same MHC no rejection

2. Isografts

A graft from 1 individual to a genetically different individual of the same species

Different MHC may cause rejection

To minimize rejection, tissue typing is done Find a close match for both tissue donor &

recipient’s MHC (at least 75% match) In the absence of identical twins, siblings

usually provide the closest tissue-type match.

3. Allografts

MHC causes rejection of tissue graft & organ transplant

To reduce rejection, chemicals are needed to suppress the immune response (immunosupressant ~ cyclosporine)

But, it causes the recipient to be more susceptible to infection during treatment

Skin Grafting & Organ Transplant

Involve major organs (heart, renal, liver, lung)

Determine ABO blood typing Determine tissue typing (MHC matching)

Organ Transplant

Selective drugs, that suppress helper T cell activation without crippling nonspecific defense or T-independent humoral responses, can improve the success of organ transplant.

Skin Grafting & Organ Transplant