Emerging Diseases Lecture 6:

Your Immune System

6.1 Overview6.2 The Immune System-Anatomy

and Cells6.3 Immune Memory

6.4 Vaccines6.5 Types of Protection

6.1: Overview: 3 Levels of Protection

• Physical and chemical barriers (hair, skin)• Innate immune system: non-specific such as

inflammation• Adaptive immune system-most important,

flexible and strong

You have three levels of protection against infectious disease

6.2 Cells and Anatomy of the Adaptive Immune System

It keeps you from being sick all the timeProvides protection against germs and invading substancesDistinguishes self from non-self

Can “learn” new diseases-aka adaptive

Has two important parts (aka branches, arms)“cellular” works through intact living cells“humoral” works through proteins dissolved in blood

Disambiguation: Two types of Immune System Disorders

Immunodeficiency: for some reason the adaptive immune system does not work

Autoimmune diseases: the immune system cannot distinguish self and non-self

This is for disambiguation and clarification-AIDS (Module 4) is an example of an

immunodeficiency disease

6.3: Anatomy of the Immune System

Many organs and tissues are involved

Dispersed throughout body

Involves circulation of blood and lymph to distribute protection

Cells Found in the Immune SystemMany different types of cells

Each specialized for a task

Activities must be coordinated

Derived from unspecialized stem cells. They keep dividing and their descendants become the worker cells of the immune system.

A second key point is that the immune system relies on stem

cells to keep dividing-thus producing more immune system

cells for continued protection.

The adaptive immune system works by detecting foreign

substances (“invaders”) and eliminating them. Foreign

substances that react with the immune system are called

“antigens”.

Antigens are foreign substances that enter your body and are perceived as a threat by your

adaptive immune system.

One way that it responds is to produce defence proteins called

“antibodies”.

Antigens are foreign substances Antibodies are your own defense

proteins

Ag = antigenAb = antibody

Antigen and antibody are two important terms that define two completely different substances-

but the substances “go together”.

How the Immune System WorksThe body detects an antigen when a macrophage becomes an APC

This signals an invader is present

Pre-existing Helper T cells respond by activating the rest of the immune system

B cells (bone marrow) and more T cells (thymus) are produced

They in turn attack and destroy the invader

Helper T calls are the “generals” in the fight against invaders.

They trigger the main response.The “soldier” cells are B calls and

other T cells.They fight the battle, but they only

attack the invader that was originally detected by the

macrophage (scouts).

This immune response is highly specific for each invader.And the immune system

remembers invaders from the past.

It does so by holding back some of the B cells and T cells in reserve.

They are called “memory” cells.

The memory cells are a pre-positioned defense system.

If the invader comes back a second time, memory cells permit a rapid

and powerful response.

The second attack by the invader does not stand a chance.

The following cartoon illustrates the production of memory B calls,

ready to fight off the invader’s second attack.

The following graph shows how memory cells allow the immune system to respond more rapidly

and more powerfully to the second attack.

6.4: How Immune Memory Works

Faster Response When There Are Memory Cells Around

Your immune system learns by building up many different memory cells.They wait around until the next time the antigen shows up.Then they cause a very fast response-too fast for the germ to take hold.

6.5: VaccinesArtificially stimulate immune system to build

memory.

They stimulate a protective response without the disease symptoms or dangers.

6.5: Vaccines-definitionsInactivated vaccine: uses killed or inactivated antigenSubunit vaccine: uses only part of antigenAttenuated vaccine: uses weakened antigenAdjuvants: a substance included in vaccine to boost the immune response-not a part of antigen

6.6: Types of ProtectionActive Immunity: your own body provides the

protectionExample: DPT vaccine protects against

diphtheria.Passive Immunity: you are given antibodies that

you did not produce in order to save your life.Examples: Antibodies from horses used to treat

diptheria, or-blood from Ebola survivors transfused into patients in emergencies.