Emerging Diseases Lecture 6: Your Immune System 6.1 Overview 6.2 The Immune System-Anatomy and Cells 6.3 Immune Memory 6.4 Vaccines 6.5 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 time Provides protection against germs and invading substances Distinguishes 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 System Many 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 = antigen Ab = antibody

Antigen and antibody are two important terms that define two completely different substances- but the substances “go together”.

How the Immune System Works The 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: Vaccines Artificially stimulate immune system to build memory. They stimulate a protective response without the disease symptoms or dangers.

6.5: Vaccines-definitions Inactivated vaccine: uses killed or inactivated antigen Subunit vaccine: uses only part of antigen Attenuated vaccine: uses weakened antigen Adjuvants: a substance included in vaccine to boost the immune response-not a part of antigen

6.6: Types of Protection Active Immunity: your own body provides the protection Example: 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.