Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Cells of the Immune System And Viral Infections Cells of the Immune System • Macrophages • Helper T cells • B cells • Killer T cells • Memory cells Immune cells and other blood cells made in bone marrow -- all are descendents of self-renewing stem cells Make variable antibodies Membrane-bound variable T cell receptors Kill cells that are missing self proteins Phagocyte Phagocyte Note these are adult stem cells, NOT embryonic stem cells. p. 4 “How the Immune System Works” by Lauren Sompayrac Microbe with protein coat enters body and starts to reproduce Immune System Response to a Microbial Infection (viruses & bacteria) Macrophages circulate thru body and ingest some of the microbes, alerting Helper T cells by presenting protein coat Helper T cells recognize protein coat of microbe and alert T and B cells by making cytokines Killer T cells kill microbe or human cells infected with microbes B cells make antibodies that neutralize microbes Memory T cells remain to provide immunity Memory B cells remain to provide immunity The Miracle of the Immune System From birth, humans have the ability for an immune system response to any microbial infection but the response is only initiated when the infection occurs After we become sick, why are we ill for about a week? After the infection starts, it takes about one week to make the T cells and B cells necessary to defeat the microbe Viral Infections Viruses Based on Harvard Medical School Family Health Guide •Viruses do not have ribosomes and cannot make their own protein •After the virus attaches to the host cell’s membrane, it injects its genetic material which directs synthesis of viral proteins What Viruses Cannot Do • • • • • • No metabolism Cannot reproduce on their own Cannot move No respiration Do not eat No cellular structures Viral Infection • Viruses penetrate epithelial surfaces and take over cells to produce more viruses • The host cell then ruptures and releases the newly produced viruses or the virus will not rupture the cell until it is stimulated by a chemical or physical agent. • Although the immune system can defeat most viral infections, some viruses can hide from the immune system and remain in the body Some contagious viral infections include: •varicella (chicken pox) •rubella (German measles) •the common cold •hepatitis •mumps •infectious mononucleosis •rubeola (measles) Antibiotics Don’t Work on viral infections!!! (and there are not many antivirals) Lytic Cycle Lysogenic Cycle Differences Between Lytic and Lysogenic Cycles Lytic Cycle Lysogenic Cycle The lytic cycle causes the host bacterium to undergo cell lysis, that is, cell destruction. The lysogenic cycle does not cause cell lysis or cell destruction. The lytic cycle can lead to production of 100 to 200 progeny phages. The DNA of the phage gets integrated into the bacterial chromosome and no progeny are produced mostly. Lysogenic cycle can be Lytic cycle cannot be converted converted into lystic cycle when into the lysogenic cycle. the host cell is exposed to chemical or physical agents. Shingles is caused by the chickenpox virus that has “hidden” in the body •After having chickenpox, some of viruses lie dormant in nerve cells near spinal cord •Years later, the virus reactivates and travels along nerve fibers to skin •As the virus moves, it causes pain •When it reaches the skin, it causes a rash and blisters Based on: Mayo Clinic Health Letter Why do we keep getting the common cold? There are over 200 viruses that cause cold symptoms Cold viruses can mutate and change their health-related effects Based on Starr, C. Biology: Concepts and Applications, Brooks/Cole The common cold: is a selflimited contagious illness that can be caused by a number of different types of viruses. Spread by contact. Transmission: Deposition of Airborne droplets •Warts: blister-like bumps caused by viruses in the skin. Transmission: Direct contact Severe Acute Respiratory Syndrome (SARS) More than 8000 people became sick worldwide 774 people died A New Strain of Lethal Cold Virus? •Previous virus strains could only survive in the throat and nasal passages because the temperature was too high deep in the chest Viral diseases: What medication are they treated with? •Acquired Immune Deficiency Syndrome: transmitted sexually and in blood products, the HIV virus attacks the Helper T cells of the immune system, causing infections that lead to death. Transmission: Bodily fluids Influenza: - we call it the “flu” - virus mutates quickly so a new vaccine is offered every year. Transmission: Deposition of Airborne droplets Smallpox: A deadly disease causing terrible scars that was wiped out by widespread vaccination several decades ago. Transmission: Direct Contact Bacterial Infections Bacteria have DNA and ribosomes and can make their own protein Based on: Mader, S., Inquiry Into Life, McGraw-Hill Binary Fission 1 bacterium can become 1/2 million in 6-7 hours Based on Harvard Medical School Family Health Guide Bacteria cause… tuberculosis, syphilis, gonorrhea, Chlamydia, Lyme disease, scarlet fever, Rocky Mountain Spotted tick fever, staph infection (MRSA) TB (tuberculosis) Lyme Disease-bulls-eye rash Scarlet Fever Rash Nails become ridged Rocky Mtn Spotted Fever MRSA (Staph Infection) Bacterial Infection • Bacteria penetrate epithelial cells and undergo rapid division. One bacterium can become 1/2 million bacteria in 6-7 hours • Bacteria can produce protein toxins that kill cells and interfere with nerve and muscle function • The immune system cannot respond rapidly enough to protect the body against the most dangerous bacteria Discovery of Penicillin: First Antibiotic •Fleming happened to observe that petri dishes with molds had killed bacteria in rings around the mold •He postulated that the “mold juice” had killed the bacteria •The mold was Penicillium notatum and the “juice” was named Penicillin Antibiotics • Antibiotics like penicillin kill bacteria by blocking cell wall formation • Antibiotics like penicillin do not kill human cells because they have no cell walls • Antibiotics like penicillin do not work against viruses because viruses lack cell walls E. Coli Outbreaks E. coli Outbreaks Swimming Pool Cabbage Patch Bad Cheese Dirty Toys What makes this E. coli strain so bad? 1. 2. 3. One strain of E. coli has extra genes that allow it to stick to the walls of the intestine and produce a potent toxin The toxin injures the cells of the intestinal wall, leading to bleeding The toxin travels in the bloodstream to the kidneys, leading to kidney failure Why is kidney failure life threatening? Answer Because kidneys are responsible for removal of nitrogenous waste (urea) and water balance. Back Based on: Mader, S., Inquiry Into Life, McGraw-Hill