Viruses and The Immune System

Human Immune System There are three levels of immune defense Primary Line of Defense: Skin and mucous barriers that prevent pathogens from entering the body Secondary Line of Defense: inflammatory response caused by an increase in WBC and fluids in a tissue Tertiary Line of Defense: Defense mechanisms that specifically target each pathogen

Primary Line of Defense The skin prevents pathogens from entering the body Sweat and oils on the skin create an acidic environment that can destroy harmful pathogens Mucous and cilia keep pathogens from entering through the mouth and nose

Secondary Line of Defense If a pathogen is able to get past the primary line of defense a non-specific response is initiated WBC and fluid leaks from the blood vessels in to surrounding tissues WBC engulf and destroy pathogens Cells produce interferon, this blocks the replication of viruses

Tertiary Line of Defense Antigens are substances that trigger a specific immune response Antibodies are produced to attach to a specific antigen When antibodies have attached themselves to viruses the virus is unable to enter a cell The virus/antibody structure is then engulfed and destroyed

Tertiary Line of Defense B-cells produce the different antibodies that we have Each B-cell only produces 1 type of antibody Once an antigen is present the specific b-cell replicates rapidly and starts producing antibodies

Immunity Once an antibody has been created we will always have a copy of it  we have immunity to that antigen The initial response to a antigen is called the primary immune response Subsequent exposures to an antigen trigger secondary responses

Vaccines Vaccines introduce an antigen to the body to allow for antibodies to be produced and ready for infections The first vaccine was created by Edward Jenner for small pox by injecting people with cowpox, a similar virus Louis Pasteur developed vaccines that were weakened or destroyed versions of the antigen