Immunity Overview

Types Of Immunity

1. Innate Immunity2. Acquired Immunity

A. Naturally Acquired Active Immunity

B. Artificially Acquired Active Immunity

C. Naturally Acquired Passive Immunity

D. Artificially Acquired Passive Immunity

Overview of Immunity

Naturally Acquired Active Immunity

Naturally acquired active immunity is obtained when a person is exposed to antigens in the course of daily life, direct exposure.

The immune system then responds by producing antibodies and specialized lymphocytes. Usually, the immunity is for a long term.

Examples, include measles, pox.

Artificially Acquired Active Immunity

Artificially acquired active immunity results from

vaccination or immunizations. Vaccination introduces specially prepared

antigens into the body.These antigens are no longer able to cause

disease, but they are still able to stimulate an immune response.

Naturally Acquired Passive Immunity

Naturally acquired passive immunity involves the natural transfer of antibodies from a mother to a child. An expectant mother is able to pass some of her antibodies to her fetus across the placenta.

In addition, certain antibodies are also passed from the mother to the child during breast feeding. Generally immunity lasts only as long as the

antibodies are active usually a few weeks or 6 months.

Artificially Acquired Passive Immunity

Artificially acquired passive immunity involves an

injection of antibodies into the body.

These antibodies come from an animal or human who is already immune to the disease.

Immunity OverviewImmunity: The body's ability to fight off

harmful micro-organisms –PATHOGENS- that invade it.

The immune system produces antibodies or cells that can deactivate pathogens.

Fungi, protozoans, bacteria, and viruses are all potential pathogens.

Antigen: Molecules from a pathogen or foreign organism that provoke a specific immune response.

The Immune System - includes all parts of the body that help in the recognition and destruction of foreign materials.  White blood cells, phagocytes and lymphocytes, bone marrow, lymph nodes, tonsils, thymus, and spleen are all part of the immune system.  

Function of the immune systemDestroy pathogensDetect and kill abnormal cellsRemove dead cells and other

debris from the body

The Immune System is the Third Line of Defense Against Infection

Third-Line Defenses - Sometimes the second line of defense is still not enough and the pathogen is then heading for the body's last line of defense, the immune system.  

The immune system recognizes, attacks, destroys, and remembers each pathogen that enters the body.  It does this by making specialized cells and antibodies that render the pathogens harmless.

 Unlike the first line and second line defense the immune system differentiates among pathogens.

For each type of pathogen, the immune system produces cells that are specific for that particular pathogen. 

An antibody is a protein produced in response to an antigen.

Antigens are macromolecules that elicit an immune response in the body. The most common antigens are proteins and polysaccharides.

Antigens can enter the body from the environment. These include

inhaled macromolecules (e.g., proteins on cat hairs that can trigger an attack of asthma in susceptible people)

ingested macromolecules (e.g., shellfish proteins that trigger an allergic response in susceptible people)

molecules that are introduced beneath the skin (e.g., on a splinter or in an injected vaccine)

antigens can be generated within the cells of the body. These include

proteins encoded by the genes of viruses that have infected a cell

Proteins that are encoded by mutant genes; such as mutated genes in cancer cells

protect against specifically identified threats (i.e. may defend against one particular bacterial infection but not a different one)

many specific defenses develop after birth upon exposure to an antigen; an antigen can be a pathogen (disease-causing organism), foreign protein (e.g. toxin), abnormal or infected body cell, foreign tissue transplant

specific defenses produce a state of long-term protection known as “Immunity”

Specific defenses

ImmunityImmunity = specific resistance to disease

depends on coordinated activity of T & B lymphocytes

Humoral immunity involves the antibodies and the B cells that they secret them; is directed against extracellular pathogens

Cellular immunity involves T lymphocyte that directly attack other cells; defense against abnormal cells & intracellular pathogens

Humoral and cellular immunity

Humoral Immunity

Cellular Immunity

Type of cells B-Cells T-Cell

Antibody Involvement

Yes No

Location of pathogen

Extracellular Intracellular

Immunity is the result of the action of two types lymphocytes, the B lymphocytes and the T lymphocytes.

B cells produce antibodies that are secreted into the blood and lymph.

  T cells attack the cells that have antigens that they

recognize.

Shared feature of B & T lymphocyteSpecificity of receptors: Both B & T

lymphocyte have specific receptor for specific antigen

Diversity of receptors: There are huge numbers of different lymphocyte each with its own unique antigen receptor

Regulation of activation: Activation of B & T cells leads to process clonal expansion

Memory: Respond to subsequent exposure to the same antigen

Antigen: Self AntigenThere are a vast number of

antigen outside the body. There are also internal antigen called self antigen.

Lymphocyte must recognize antigen from pathogen while ignoring self antigen

Antigen receptor- SpecificityThe surface of mature B & T lymphocyte

studded with lymphocyte antigen receptor that allows these cells to identify their particular antigen shape

The antigenic specificity of B & T lymphocyte is determined by the shape of their antigen receptor

B & T cells have a related structure and similar function, there are differences in their shape and the way they interact with antigen

Antigen receptorThe B cell antigen receptor is Y-

shape antibody molecule and directed against antigen in the extracellular fluid

When the antigen occupy the antigen binding site on the B cell receptors, the receptor signals the cell that antigen found

Antigen receptorT lymphocyte receptor is not:1. Membrane bound antibody2. Y-Shaped T cell directed against the

body’s own cells when they are invaded

Antigen receptorWhen antigen bind receptors and

activate the receptors, the cell divides and make clone with identical receptor

This matching mechanism called clonal selection

Humoral (Antibody-Mediated) Immunity◦ Involves production of antibodies against

foreign antigens.◦ Antibodies are produced by a subset of

lymphocytes called B cells.◦ B cells that are stimulated will actively secrete

antibodies and are called plasma cells.◦ Antibodies are found in extracellular fluids

(blood plasma, lymph, mucus, etc.) and the surface of B cells.

◦ Defense against bacteria, bacterial toxins, and viruses that circulate freely in body fluids, before they enter cells.

◦ Also cause certain reactions against transplanted tissue.