Immune SystemImmune System

The Immune SystemThe Immune System

The function of the immune system The function of the immune system is to fight infection through the is to fight infection through the production of cells that inactivate production of cells that inactivate foreign substances or cellsforeign substances or cells

This process is called This process is called immunityimmunity

First Line of DefenseFirst Line of Defense

The function of the first line of defense is The function of the first line of defense is to keep pathogens out of the body.to keep pathogens out of the body.

This role is carried out by skin, mucus, This role is carried out by skin, mucus, sweat, and tears.sweat, and tears.

Your body’s most important non-specific Your body’s most important non-specific defense is the skindefense is the skin

Mucus, saliva, and tears contain Mucus, saliva, and tears contain lysozyme.lysozyme.

Lysozyme Lysozyme breaks down the cell wall of breaks down the cell wall of many bacteria.many bacteria.

Second line of defenseSecond line of defense

If pathogens do enter your body, If pathogens do enter your body, they may replicate rapidly and they may replicate rapidly and release toxins.release toxins.

When this happens, the inflammatory When this happens, the inflammatory response is activated,response is activated,

The inflammatory response is a non-The inflammatory response is a non-specific response to tissue damage specific response to tissue damage caused by injury or infection.caused by injury or infection.

The Inflammatory ResponseThe Inflammatory Response

When pathogen are detected, the When pathogen are detected, the immune system produces millions of immune system produces millions of white blood cells – lymphocytes, white blood cells – lymphocytes, which fight the infectionwhich fight the infection

Blood vessels near the wound Blood vessels near the wound expand to allow more white blood expand to allow more white blood cells to enter the tissues.cells to enter the tissues.

FeverFever

The immune system also releases The immune system also releases chemicals that increase the core chemicals that increase the core temperature of the body.temperature of the body.

A fever is advantageous because A fever is advantageous because many pathogens can only survive many pathogens can only survive within a narrow temperature range.within a narrow temperature range.

InterferonsInterferons

When viruses enter cells, sometimes When viruses enter cells, sometimes the cell will produce a chemical the cell will produce a chemical called interferon – because it called interferon – because it interferes with viral replication.interferes with viral replication.

This gives the specific immune This gives the specific immune response more time respond.response more time respond.

Specific DefensesSpecific Defenses

A substance that gets past the non-A substance that gets past the non-specific defenses, will trigger an specific defenses, will trigger an immune response.immune response.

A substance that triggers an immune A substance that triggers an immune response is called an response is called an antigen.antigen.

Specific Immune DefencesSpecific Immune Defences

The cells of the immune system that The cells of the immune system that recognize specific antigens are two types recognize specific antigens are two types of lymphocytes (white blood cells)of lymphocytes (white blood cells)

B lymphocytes (B lymphocytes (B cellsB cells) and T lymphocytes ) and T lymphocytes ((T cellsT cells))

B cells provide immunity in the body fluids B cells provide immunity in the body fluids ((humoral immunityhumoral immunity))

T cells provide a defense against abnormal T cells provide a defense against abnormal cells and pathogens in side cells. (cells and pathogens in side cells. (cell-cell-mediated immunity)mediated immunity)..

Humoral ImmunityHumoral Immunity

When a pathogen invades the body, When a pathogen invades the body, its antigens are recognized by a its antigens are recognized by a small fraction of the body’s B cells.small fraction of the body’s B cells.

These B cells grow and divide rapidly These B cells grow and divide rapidly producing producing plasma and memory cellsplasma and memory cells

Plasma cellsPlasma cells release release antibodiesantibodies..Memory cellsMemory cells remain in the body long remain in the body long

after the antibodies have neutralized after the antibodies have neutralized the infection.the infection.

AntibodyAntibody

Cell-Mediated ImmunityCell-Mediated Immunity

The body’s primary defense against The body’s primary defense against its own cells when they have become its own cells when they have become cancerous or infected by a virus is cancerous or infected by a virus is called cell-medicated immunity.called cell-medicated immunity.

Cell-Mediated ImmunityCell-Mediated Immunity

During cell-mediated immunity, T cells During cell-mediated immunity, T cells divide and differenciate into killer T cells, divide and differenciate into killer T cells, helper T cells, suppressor T cells, and helper T cells, suppressor T cells, and memory T cells.memory T cells.

Killer T cells track-down and destroy the Killer T cells track-down and destroy the bacteria, fungi, protozoan, or foreign bacteria, fungi, protozoan, or foreign tissue that cantains the antigen.tissue that cantains the antigen.

Helper T cells make memory T cells for Helper T cells make memory T cells for future attack by same pathogen.future attack by same pathogen.

Suppressor T cells release chemicals that Suppressor T cells release chemicals that shutdown killer T cells.shutdown killer T cells.

The very end……The very end……