MICROBIOLOGY MIC 201

Chapter 5- Immune response

FOREIGN INVADERS



Called

Pathogens

 Viruses, bacteria or other living thing that causes disease/immune response.



Antigens

 Toxins that pathogens produce that cause harm to an organism.

 A foreign substance, when introduced into human body, stimulate formation of specific antibodies or sensitized lymphocytes

THIRD LINE OF DEFENSE – SPECIFIC IMMUNE RESPONSE

This is a specific response to a specific pathogen/antigen.



The response involves the creation of Antibodies.

Clonal selection hypothesis: One of many B cells responds to a particular antigen and begins to divide, thereby producing a large population of identical B cells (a clone

)

Process of clonal selection explain why/how adaptive immune response act against any antigen.

•

Lymphocyte developed –with antigen receptor.

•

Then speciallized into B-cell receptor and T-cell receptor .

•

The receptor can react with specific epitopes of an antigen .

•

Each of receptor is different /identical .

•

Therefore cell has only one antigen specificity (can bind to only one antigen).

•

And all cells clone differ from another clone by the specificity of its antigenic receptor.

•

As a general rule the specificity of one unique antigen receptor expressed by one given lymphocyte is not changed throughout the lymphocyte life.

ANTIBODIES      Y-shaped

protein

molecule.

Made up of

constant variable

regions.

and Made up of

Heavy

chains.

and

Light

Produced by B-Lymphocytes

Function:

Recognize antigens, bind to and deactivate them.

 Note: Variable region recognizes the anitgens.

HOW AN ANTIBODY OPERATES/WORKS?

Deactivation of a bacterium by an antibody.

THE PATHWAY OF SPECIFIC IMMUNE RESPONSE Step 1

Pathogens eaten by Macrophage

Step 2

Displays portion of Pathogen on surface

Step 3

Pathogens Helper-T cell recognizes Pathogen

Activates Cytotoxic T- Cell Activates B- Cell Kills Infected Cells Memory T-Cell Memory B-Cell Antibodies



CELLULAR IMMUNITY .VS. ANTIBODY IMMUNITY

Cellular Immunity Antibody or Humoral Immunity

 Carried out by T-Cells  Infected cells are killed by Cytotoxic T –Cells.

  Carried out by B-cells Antibodies are produced and dumped into blood stream.  Antibodies bind to antigens and deactivate them.

3.

4.

1.

2.

IMMUNE RESPONSE EXPLAINED

Antigen infects cells.

Macrophage ingests antigen and displays portion on its surface.

Helper T- Cell recognizes antigen on the surface of the macrophage and becomes active.

Active Helper T-Cell activates Cytotoxic T-Cells and B-Cells.

5.

6.

7.

8.

Cytotoxic T-Cells divide into Active Cytotoxic T-cells and Memory T – Cells.

Active Cytotoxic T-Cells kill infected cells.

At the same time, B-Cells divide into Plasma Cells and Memory B- Cells.

Plasma cells produce antibodies that deactivate pathogen.

9.

10.

Memory T and Memory B cells remain in the body to speed up the response if the same antigen reappears.

Supressor T-Cells stop the immune response when all antigens have been destroyed.

IMMUNE RESPONSE SUMMARY Antigen Displays copy of antigen on surface of cell Macrophage

Cellular Immunity

Active Cytotoxic T-Cell

Kills Infected Cells

Memory T- Cell Helper T - Cell Plasma Cell Antibodies

Antibody Immunity

Active B - Cell Memory B-Cell Deactivates Antigens

PRIMARY .VS. SECONDARY IMMUNE RESPONSE 

Primary Immune Response

 This is a response to an invader the First time the invader infects the body.

  No measurable immune response for first few days.

Next 10 – 15 days antibody production grows steadily 

Secondary Immune Response

 A more rapid response to an invader the 2 nd the body.

 time it invades Antibody production increases dramatically and in a much shorter time period..

GRAPH OF PRIMARY .VS. SECONDARY IMMUNE RESPONSE

Primary and Secondary Responses to an Antigen

a -1 st /initial antigen A exposure b - antibodies A produced c - antibodies during reinject of same antigen d - new antigen B exposure e - antibodies B produced

1.

PASSIVE .VS. ACTIVE IMMUNITY    Active Immunity This is immunity where the body is “actively” producing antibodies to fight infection.

Ex: You have a throat infection and you are actively creating antibodies to fight it.

Vaccination:

antibodies).

An injection of a

weakened strain

of an infectious microbe (pathogen) that causes the body to undergo active immunity (produce 2.

   Passive Immunity This is immunity where antibodies are given to a person from the blood of another person or animal.

This immunity only lasts for a short period of time.

 ex: Breastfeeding mothers pass antibodies to their children through the milk.

preformed antibody from animal or man( immune person) are given to a non immune person.