What is resistance? Susceptibility?
RESISTANCE - the ability to ward off disease
SUSCEPTIBILITY - lack of resistance
What is species resistance?
certain species contract certain diseases, while others do not, usually bc they lack specific receptors that the pathogen needs to bind to in order to infect the organism
What mechanical barriers does the body possess?
skin and mucous membranes: physical barrier, keratin resistant to weak acids and bacterial enzymes and toxins, shedding of dead cells
How do cilia help? Coughing or vomiting?
- fine hairs (cilia) lining your windpipe move mucus and trapped particles away from your lungs
- coughing and sneezing remove harmful substances by flushing action
How does a lowered pH help the body? Where does this occur?
- a decrease in pH decreases and prevents growth of bacteria and fungi in the body
- sebaceous glands produce sebum (fatty acids), lactic acid on the skin, accumulation of salt, gastric juices, vaginal secretions, and lysozymes
What is lysozyme? Where is it found?
LYSOZYME => enzyme that destroy bacteria
found in tears, perspiration, saliva, and tissue fluids
How does your normal microbiota (bacteria on your skin) protect you?
inhibits the growth of pathogens by producing antibodies
How do transferrins prevent the growth of microbes?
TRANSFERRINS => proteins that tie up the free iron in the blood and interstitial fluid (they create an antimicrobial substance)
How does interferon work? Does it help the cell that made it?
INTERFERON => a glycochemical produced by the virus infected cells that cause neighboring cells to produce anti-viral proteins, enhance phagocytosis, and suppresses growth of tumor cells (does not help the cell that made it bc it is already infected)
What is complement, and in what three ways does it act?
part of the immune system that enhances (complements) the ability of antibodies and (opsonization) phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and (cytolysis) attack the pathogen’s cell membrane
How does fever help the body fight off infection?
fever causes liver and spleen to confiscate iron and zinc needed by microbes
- increases phagocytosis
- inhibits growth of microbes
- speeds up body repair
What are the four cardinal signs of inflammation?
1 - heat 2 - swelling 3 - redness 4 - pain 5 - sometimes loss of function
What are the three stages of inflammation?
1 - vasodilation and increased permeability of blood vessels
2 - phagocyte migration (neutrophil come first, then macrophages)
3 - tissue repair
Which one accounts for most of the signs of inflammation?
stage 1 - vasodilation and increased permeability of blood vessels
What is phagocytosis?
PHAGOCYTOSIS => “cell eating” or the process by which a cell engulfs a solid particle
What are the body’s two major types of phagocytes?
What is chemotaxis?
CHEMOTAXIS => the process by which neutrophils and other various WBCs migrate up the gradient of chemotactic agents to the site of injury where they devour any foreign material
What other steps are involved in phagocytosis?
1 - chemotaxis
2 - adherence
3 - ingestion
Why is adherence of the phagocyte to a bacterium sometimes difficult? What makes it easier?
- adherence can be difficult because some bacteria have external capsules that conceal their carbohydrate signatures allowing them to elude capture because phagocytes cannot bind to them
- Opsonization, coating pathogen’s with opsonins, which are complement proteins or antibodies that provide handles to which phagocyte receptors combined
What are natural killer cells? Do they have the same specificity as B cells and T cells? What do they look for on their target cells?
- Natural killer (NK) cells are a group of defensive sells (lymphocytes) that lyse or kill cancer cells and virus-infected body cells before the adaptive immune system is activated [can kill a variety of microbes, tumor cells]
- NK cells are not as specific as the B and T cells of the adaptive immune system
- NK cells look for MHC on the surface of cells; they will attack the cell if no MHC is present
What is the “magic word” when talking about immunity? What is the “magic number”?
magic word of immunity: SPECIFIC
magic number of immunity: 2
What is an antigen? What characteristics make for a good antigen? What types of molecules fit that description?
ANTIGEN => any substance that elicits an immune response
- best antigens are: large, complex, recognized as foreign
- foreign proteins, large polysaccharides, some lipids and nucleic acids
What is a hapten?
HAPTEN => molecules that are small, foreign and complex
- to elicit an immune response, they must piggy-back on a larger molecule, often blood proteins
What is an epitope?
EPITOPE => a foreign protein may result in several different antibodies
- each antibody recognizes a different portion of the protein (these regions are called epitopes or antigenic determinants)
What is an Antigen Presenting cell, and what does it do? What type of cell does it activate?
APC => an immune cell that detects, engulfs, and informs the adaptive immune response about an infection
- activates T cells
What is MHC II?
MHC II => proteins found only on the surface of cells that present antigens to CD4 cells (dendritic cells, macrophages, B cells)
How is MCH II the same as the MHC I and how is it different?
BOTH are synthesized in the rough ER
BOTH are bound to peptide fragments
BUT the peptide fragments for MHC II are longer
What is a cytokine?
a protein hormone which regulates normal cell functions, like growth and differentiation
What cytokine does the macrophage produce when the helper T cell binds to it?
What cytokine does the helper T cell produce, and what does it do? (How is it different for CMI and AMI?)
T helper cell produces Interleukin-2 (this causes lymphocytes to multiply)
What cells produce humoral or antibody mediated immunity?
What two types of cells are formed when B cells are activated?
PLASMA CELLS => produce large quantities of their specific antibody into the blood
MEMORY CELLS => wait for the next infection to occur
What are antibodies?
ANTIBODIES => the gamma globulin part of blood proteins
What does an antibody molecule look like, and how does it work?
looks like Y-shaped molecules with two regions: Fab region (variable region that matches a specific antigen) and Fc region (constant region that activates complement
- antibodies respond to specific antigens and bind them to antigen binding sites
What is IgM? IgG?
IgM => the first antibodies produced; very effective in opsonization and activating complement (10 binding sites)
IgG => produced several days later; single unit antibodies, abundant in serum, cross the placenta, and has longest half-life
Where would you find IgA’s?
in mucus, tears and other secretions
How does cell mediated immunity resemble AMI (antibody-mediated immunity)?
AMI tags antigens, but does not destroy them while preparing them for destruction by macrophages and cells with antigen destroying capability
How does a Tc cell kill a virus-infected cell? (Two possible ways)
1 - Tc cells bind to antigens on infected cells and release:
PERFORINS - punch holes in cell membrane
GRANZYMES - proteases that induce apoptosis
LYMPHOTOXINS - activate the cell’s own self-destruct mechanism
2 - Tc cells bind to specific membrane receptors on the target cell to stimulate apoptosis
What is a primary immune response?
the first time you encounter an antigen, you have few B cells or Tc cells against that antigen
What is a secondary immune response?
the next time, you have many memory cells, so response is much quicker, so you don’t come down with the disease
How do follicular dendritic cells help maintain immunity?
follicular dendritic cells can become natural killer cells
How does delayed type hypersensitivity occur? What cells are involved, and what type of reaction do they cause?
delayed hypersensitivity => a type of cell-mediated immunity
- occurs when it takes time for your body to react to microbes, such as in a TB skin test
- Td cells produce several cytokines that attract and activate macrophages, resulting in inflammation
What type of immune reaction is immediate type hypersensitivity? What immunoglobulins are involved, and what happens when they bind with an allergen?
immediate hypersensitivity => humoral (antibody-mediated) immune reaction
- IgE (is involved) antibodies bind to mast cells by the Fc end (when encountered again, binding with the antibody causes mast cell to release histamine)
What happens if these reactions occur throughout the body?
if hypersensitivity reactions occur throughout the body, histamine is released
How can we counter the effects of immediate type hypersensitivity?
we may be able to desensitize individuals by given allergens to stimulate IgG antibodies that tie up the antigen before they can bind with IgE
What is delayed-reaction allergy or delayed hypersensitivity? What type of immune response is involved? What is autoimmunity?
- delayed hypersensitivity is a common immune response that occurs through direct action of sensitized T cells when stimulated by contact with antigen
- referred to as a delayed response in that it will usually require 12–24 hours at a minimum for signs of inflammation to occur locally
AUTOIMMUNITY => the system of immune responses of an organism against its own healthy cells and tissues
What is a tissue rejection reaction? What is graft-versus-host disease?
- when transplanted tissue is rejected by the recipient’s immune system, which destroys the transplanted tissue
GVHD => condition that occurs when donor bone marrow or stem cells attack the recipient
What are the four types of grafts (transplant tissues)?
AUTOGRAFT - grafting one part of the body to another location in the same individuals; no chance of rejection, includes skin graft, taking vein from leg to use in a heart surgery
ALLOGRAFT - grafting between two non-identical member of same species but not same genotypes; includes the transplantation of heart, kidney, lung etc, from a members who donate their organs; anti-rejection drugs or immunosuppressant need to be taken to prevent the body from rejecting a transplanted organ
ISOGRAFT - grafting between two individuals, are identically twins or genetically same (since they have the same genetics there is no chances of graft rejection)
XENOGRAFT - grafting between two individuals of different species; most commonly from animal to man (such as pig heart valve used to replace human); more chance of graft rejection and to reduce the rejection, person might need immunosuppressant as in allografts
What is an example of inherited immunity? Acquired immunity?
INHERITED - children are born either without an immune system or with an incomplete immune system due to a genetic defect
ACQUIRED - immunity acquired by infection or vaccination (active immunity) or by the transfer of antibody or lymphocytes from an immune donor (passive immunity)
Explain and give an example of natural active immunity.
person comes down with measles will never get it again
Explain and give an example of artificial active immunity.
person is immunized with a vaccine
Explain and give an example of natural passive immunity.
person receives serum with antibodies (only good as long as the antibodies exist, ~month, then will become susceptible again)
Explain and give an example of artificial passive immunity.
colostrum from mother’s milk gives baby immunity for the first 30-90 days of life
Which lasts longer, active immunity or passive immunity? Why?
ACTIVE IMMUNITY lasts longer
- passive immunity results when antibodies are transferred to a person who has never been exposed to the pathogen
- passive immunity lasts only as long as the antibodies survive in body fluids (usually between a few days and a few months)