Pathogens and The Immune System

What is a virus? Latin word for poison Segments of RNA or DNA surrounded by a protein coat. Tiny, non-living Invade living things

CELLVIRUS Made of cellsYESNO Obtain & use energyYESNO Grow & developYES Only inside a living cell ReproduceYES Only inside a living cell Respond & adaptYES Contain RNA or DNAYES Characteristics of life

VIRUS STRUCTURE Envelope (part of the protein coat) Capsid – right inside the envelope (part of the protein coat) Nucleic acid (either DNA or RNA) ENVELOPE NUCLEIC ACID CAPSID Protein markers help virus recognize their host

Retrovirus A virus that contains RNA instead of DNA Human Immunodeficiency Virus (HIV) is a retrovirus Genetic information is copied backwords, from RNA to DNA instead of DNA to RNA. ENVELOPE RNA CAPSID

Viruses: Bacteriophage A virus that only infects bacteria CAPSID DNA TAIL FIBER HEAD Tail Aids in attachment

Why do scientists consider viruses to be non-living things? Do not grow Do not eat (metabolism) No homeostasis Do not breath Cannot reproduce on their own – must infect a living cell.

Comparison of virus and living cells

Here are 3 viruses…T4; Tobacco mosaic and HIV…all they have is a nucleic acid core and a protein coat T4 Tobacco mosaic HIV

The two life cycles of a virus… Once inside a cell a virus can do one of two things…  LYTIC cycle: enters cell, makes copies of itself and causes the cell to burst. Destroys host cell  LYSOGENIC cycle: slower cycle, virus integrates it’s DNA into the hosts DNA. Viral DNA is embedded in host’s DNA. host’s body triggers the virus into action takes a long time for the virus to take affect (like HIV)

Viral Replication (virus reproduction) 1.Attachment 2.Injection of genetic material into the host 3.Making of new parts 4.Assembly of parts 5.Release of new viruses

Viral Disease in Humans Unlike bacterial diseases, viral diseases can’t be treated with antibiotics. Vaccines are used for the prevention of some viral diseases. Once someone has contracted a viral disease, they can only treat the symptoms to make themselves feel better until the infection clears up on its own. Disinfectants can be used to kill viruses on household surfaces.

SEM of a bacteriophage virus

Bacteriophage infecting a bacteria

Lytic cycle animation mic/offsite.htm?site= y.ccbcmd.edu/courses/bio141/lecg uide/unit3/viruses/adlyt.htmlhttp://biology.about.com/gi/dyna mic/offsite.htm?site= y.ccbcmd.edu/courses/bio141/lecg uide/unit3/viruses/adlyt.html

A host cell in the lysogenic phase can suddenly convert to the lytic stage…this happens with HIV…when it does, HIV becomes AIDS.

Viral Disease in Humans Unlike bacterial diseases, viral diseases can’t be treated with antibiotics. Vaccines are used for the prevention of some viral diseases. Once someone has contracted a viral disease, they can only treat the symptoms to make themselves feel better until the infection clears up on its own. Disinfectants can be used to kill viruses on household surfaces.

Immune System

Infectious and Non-infectious Disease Infectious – can spread from person to person or from one body part to another, caused by a pathogen in the body Non-infectious – does not spread - arthiritis

DISEASE TRANSMISSION: 5 ways to spread an infectious disease 1.Person to person contact- STD’s, colds, strep throat 2.Air-colds 3.Food – botulism (swollen cans) 4.Water- infected with sewage 5.Animal bites- mosquitos transmit malaria, dogs transmit rabies

Disease Transmission Robert Koch established a procedure for diagnosing causes of infection. His 4 step procedure is called Koch’s postulates.

Disease Prevention and Protection Immunity – resistance to a particular disease. Vaccination – invented by Edward Jenner. Used to produce immunity. Vaccines contain a dead or weakened pathogen.

Your Bodies Defenses: chapter 40 Body uses specific and nonspecific defense mechanisms to detect and destroy pathogens. 1 st LINE OF DEFENSE: SKIN nonspecific (do not target certain diseases, tries to kill anything) acts as a barrier, oil and sweat keep many diseases from growing. mucous membranes –line entrances and exits of the body and trap pathogens when they enter. move to second line if the skin is broken.

2 nd LINE OF DEFENSE: nonspecific4 important nonspecific. 1. Inflammatory response – series of events that suppress infection and speed up recovery. Infected cells release histamine – causing blood (including WBC’s) to rush to the site. Causes swelling and redness. Pus contains WBC’s, dead cells and dead pathogens.

2 nd LINE OF DEFENSE: 2. Temperature response – when the body is fighting a pathogen. Fever makes it harder for pathogens to grow, very high fever can be dangerous and even kill you. 3.Proteins – circulate in the blood and become active when they run into certain pathogens.

2 nd LINE OF DEFENSE: 4.White blood cells – patrol the bloodstream and attack pathogens. 3 types 1. Neutrophil – englufs and destroys. Most abundant type. 2. Macrophage – ingest and kill pathogens, clear dead cells and debris from the body. 3. Natural Killer cells – large WBC that attacks infected cells causing the cell to swell and burst. Kill cancer cells.

Walking macrophage" A major player in the body's immune system, this white blood cell is probing an airsac in a human lung with pneumonia. It was looking for debris, bacteria or other foreign matter that it would have ingested like a tiny vacuum cleaner. x7000

A large cancer cell surrounded by natural killer cells

3 rd LINE OF DEFENSE: The Immune Response SPECIFIC DEFENSES Occurs when bodies nonspecific defenses get overwhelmed. Army of individual cells that go to war for the body attacking specific pathogens.

3 rd LINE OF DEFENSE: The Immune Response: Cells Involved 4 Different types of white blood cells – 1. Macrophages- can attack any (not specific) consume pathogens. 2. Cytotoxic T cells – attack and kill 3. B Cells – remember and label invaders and instruct macrophages when to attack. 4. Helper T cells – activate T and B cells.

3 rd LINE OF DEFENSE: The Immune Response: Recognizing Invaders -The infected body cells have ANTIGENS on their surface. Antigens trigger the immune response. WBC’s recognize and respond to the antigens -ANTIBODIES – proteins that bind to antigens

Oh no – you have the flu- What happens? You just took a deep breath, the air contained the flu virus. Here’s what happens: Some were trapped in mucus, but a few slipped past. You now have infected cells. Macrophages begin engulfing and destroying the infected cells.

2 Main parts of the Immune Response 1.B cell response 2.T cell response T and B cells are produced in the bone marrow.

Disorders of the Immune system AUTOIMMUNE DISEASES – immune system cannot distinguish between the body’s antigens and foreign antigens. Body begins fighting itself. Examples: MS (Multiple Scelrosis) Arthritis Lupus Diabetes

HIV - retrovirus Human immunodeficiency disorder HIV attacks helper T cells weakening the immune system. Transmitted by body fluids. Most commonly transmitted through sexual contact and needles. Mosquitos and ticks CANNOT transmit HIV.

Allergies Inappropriate response by the immune system. Antigens bind to cells in the nose and release histamine. Histamine causes redness, swelling, runny nose, itchy eyes and congestion. Take antihistamines – sudafed, etc, to fight allergies.