Vaccines, Viruses and the Immune System

Immunity and Vaccination Immunity is the ability to resist an infectious disease. Immunity can come about in two ways: surviving an initial infection vaccination. Vaccination is the introduction of antigens into the body to cause immunity, usually through injection.

Immunity and Vaccination A vaccine is a solution that contains a dead or weakened virus or material from a virus that still contains antigens (proteins) The immune system will produce an immune response to the viral antigens (called the primary response). Q: Why do you sometimes feel slightly ill after receiving a vaccination even though you’re not truly “infected”?

Endocrine, Circulatory and Immune Systems: Working Together! The immune system includes both the cells and the tissues / organs that recognize and attack foreign substances in the body. The components of the immune system are found throughout the body.

Autoimmune Diseases An autoimmune disease occurs when the immune system attacks an organism’s own cells. Autoimmune diseases can affect organs and tissues in various areas of the body.

On The Attack! A macrophage is a white blood cell that engulfs and destroys pathogens (viruses and other materials that cause disease) Natural killer cells are white blood cells that attack virus-infected cells

Cytotoxic T Cells Cytotoxic T cells recognize and destroy cells that have been infected by a pathogen. They respond to viral antigens that appear on the surface of an infected cell and attack.

Recognizing Pathogens Lymphocytes (white blood cells) can provide specific defenses because they recognize pathogens by the antigens on their surface. An antigen is any substance that the immune system does not recognize as part of the body. It is usually some type of protein.

Recognizing Pathogens Because the lymphocytes do not recognize the antigen as “self”, they start a specific attack known as an immune response. Lymphocytes recognize a pathogen with molecules on their surface called receptor proteins.

Recognizing Pathogens An antigen has a complementary three-dimensional shape that allows the receptor protein to bind to it. This is how the lymphocyte recognizes the antigen. Only the specific receptor protein that is complementary to the antigen will be able to bind there.

VIRUSES

What Is A Virus? 1) Virus - a nonliving particle made up of nucleic acid and a protein coat or nucleic acid and a lipid protein coat.

Are Viruses Alive? 2) Criteria Yes Kind of No Reproduce Energy Use Adapt Cells Homeostasis Nucleic Acids (must have both) Growth Organization

Are Viruses Alive? 3 and 4) Are they alive? No, they would have to meet all 8 qualifications to be considered alive. Even though viruses do have genetic material, or a genome, they cannot reproduce outside their host cell. They must enter a living cell and use the host cell’s ribosomes, ATP, enzymes, and other molecules to reproduce.

Viral Structure 5) Capsid - the protein coat surrounding the nucleic acid.   6) Envelope - Some viruses have a bilipid membrane that surrounds the capsid; help new viruses recognize host cells.

Classification of Viruses 7) Viruses can be classified based on: Linear or circular genome Shape of their capsid Whether they have DNA or RNA Presence of an envelope DNA or RNA is either 1x or 2x stranded 8)

Hosts 9) Bacteriophages - viruses that infect bacteria. Viruses infect both prokaryotes and eukaryotes.

Viral Transmission 10) Outside the host cell, a virus is a lifeless particle with no control over its movements. It is spread by: Air In water In food By body fluids

Viral Reproduction 11) Lysogenic Cycle - Viral DNA is inserted into the host’s genome but is not transcribed or translated. Allows viruses to hide in their host cells for days, months, or years. 12) Temperate virus - viruses whose replication cycle includes the lysogenic cycle.

Reproduction Cycles 13) Lytic Cycle- viruses enter a cell, produce new viruses, and rupture (lyse) the cell.   14) Virulent viruses- viruses that reproduce only by the lytic cycle.

Ebola vs. HIV: Which type of virus is each one? Ebola – The virus causes progressively worsening symptoms 4-10 days after infection. Death is the result in 80-90% of infections. = lytic, virulent HIV – The virus that causes AIDS targets and infects T Cells and can lay dormant for months to years before wiping out the immune system. = retrovirus – lysogenic, temperate