Defenses Against Infection Human Immune System

KEY CONCEPT The immune system has many responses to pathogens and foreign cells.

The job of the immune systems is to fight off pathogens & infections. Skin is a physical barrier to infection. Mucous Membranes trap pathogens entering the body.

Nonspecific responses First Line of Defense: Skin – few pathogens can penetrate the layers of dead skin cells Mucous membranes

Second Line of Defense: Inflammation - blood vessels become leaky. Histamines & interferons Fever - body temperature increases Slows growth of pathogens Low fevers stimulate white blood cells to mature.

Cells of the immune system produce SPECIFIC RESPONSES Specific Immune response: Antigens are surface proteins on pathogens. Each pathogen has a different antigen. antigens

Recognizing Self Your body’s white blood cells use antigens to recognize “self” versus “other”. Your body then works to inactivate or destroy “other”

Attacking Invaders/Pathogens Phagocytes (like Pacman) consume pathogens and present the pathogen’s antibodies to other white blood cells.

Antibodies Produced by lymphocyte Bind to foreign antigens Each antibody is specific for a particular antigen Body can make 10B different antibodies!!! Tag foreign cells for destruction by other WBCs

Lymphocytes B – Cells Made in bone marrow Each recognizes a single antigen Once activated they produce Memory B cells & plasma cells Memory B cells remain after infection Memory B cells allow a rapid response during re-infection

Lymphocytes T – Cells Made in bone marrow, mature in thymus Each recognizes a single antigen Helper T-cells Activate B-cells Activate killer T-cells Produce memory T-cells

Vaccines Allow person to acquire immunity without contracting disease Contain the antigen of a weakened pathogen Does not cure a person who is sick

–stimulates a specific immune response –causes memory B & T cells to be produced –allows immune system to respond quickly to infection next time –has such a fast response, a person will not get sick A memory B cell is stimulated when the real pathogen binds to it. 2 The B cell quickly activates and makes antibodies that fight the pathogens before you get sick. 3 Antigens in a vaccine trigger an immune response, and memory B cells are made. 1 memory B cells Vaccination provides immunity. Memory B-cells