The Immune System Flashcards
What is a pathogen?
Bacteria, fungi, virus, etc…
How does innate immunity work? Is it fast or slow?
Recognizes traits that are shared by a broad range of pathogens using a small set of receptors.
Rapid response
Do all animals have innate immunity?
YES
What are the two types of defenses that the innate immunity provides humans with? What do these defenses consist of?
Barrier defenses - skin, mucus membranes, secretions
Internal defenses - Phagocytic cells, NK cells, antimicrobial proteins, inflammatory response
How does adaptive immunity work? Is it fast or slow?
The recognition of traits specific to particular pathogens using a vast array of many receptors.
Slower response
Do all animals have adaptive immunity?
NO, just vertebrates.
What are the two responses of the adaptive immunity and what do they consist of?
Humoral response - antibodies defend against infection IN BODY FLUIDS
Cell-mediated response - cytotoxic cells defend against infection IN BODY CELLS
Describe the innate immunity of invertebrates, for example an insect, separate into barrier and internal defenses.
Barrier - exoskeleton, digestive system has low pH and lysozyme (break down cells walls of bacteria)
Internal - Hemocytes in hemolymph carry out phagocytosis and secrete AMP (antimicrobial peptides), bacteria and fungi are recognized due to their unique molecules on cell walls and the immune response varies based on the class of pathogen encountered.
Understand this picture that covers phagocytosis
DO IT
Look at this graph of fruit fly infection and understand how different AMPs help to defend against DIFFERENT pathogens in the innate immunity.
Mutants produce no AMPs.
Drosomycin and defensin are AMPs
Have a basic understanding of antiviral defense in insects based on this picture. The steps are listed in the book.
:)
For vertebrates, describe the different barrier defenses that are present in the innate immunity. What is the purpose of mucus?
Barrier defenses:
Skin
Mucus membranes of digestive, respiratory, urinary, and reproductive tracts. Mucus traps microbes and other particles
Saliva, mucus, and tears contain lysozyme that destroy susceptible bacteria
Low pH of skin and digestive system prevents microbe growth
Describe TLRS of the internal defense of innate immunity that are present in phagocytic cells, what are the 4 types of phagocytes found in mammals?
Phagocytes:
Phagocytes have TLRs - toll-like receptors, bind to lipopolysaccharide (endotoxin), flagellin, and other pathogenic proteins.
Mammalian Phagocytes:
Neutrophils - most abundant
Macrophages - Large, found throughout the body and are part of lymphatic system
Eosinophils - release destructive enzymes to combat MULTICELLULAR INVADERS (like worms)
Dendritic cells - stimulate development of adaptive immunity
What do dendritic cells have that distinguish them?
Tree-like branches
What is the difference between a monocyte and a macrophage?
Monocytes reside in the blood stream, but when they migrate to tissues they become macrophages OR dendritic cells.
What is the other cell type that are a part of the internal defense of the innate immunity? What is their function?
NK cells - help recognize and eliminate certain diseased cells,.
What is an example of a diseased cell that NK cells might eliminate?
Cancerous or infected cells.
How does an NK cell know when a cell is cancerous or diseased?
Normally all nucleated cells in the body have MHC (major histocompatibility complex) class I proteins on their surface.
Cancerous of infected cells no longer express this protein, so NK cells know they need to be eliminated.
What is an example of a cell that doesn’t have a nuclei, and, therefore doesn’t express MHC class I?
RBCs.
Where is the lymphatic system do both macrophages and lymphocytes reside to engulf pathogens?
The spleen and lymph nodes
Describe the antimicrobial peptides and proteins portion of the internal defenses of the innate immunity in vertebrates. What are interferons and the complements system?
Pathogens that are recognized in mammals stimulate the release of peptides that attack microbes. Some of these are similar to the AMPs that are released in insects.
Interferons - proteins that provide innate defense against viruses and help to activate macrophages. These are released from the infected host cells to neighboring cells to tell them to INTERFERE.
Complement system - made up of about 30 proteins, causes lysis of invading cells and to help trigger inflammation. Produced by liver and circulate in an inactive state.
Where are NK cells derived from?
LYMPHOID STEM CELLS
What are the four cardinal signs of the inflammatory response that is part of the internal defense of innate immunity?
Redness (rubor, erythema) - increased blood flow
Heat (calor) - increased blood flow
Swelling (tumor, edema) - leaky blood vessels
Pain (dolor)
What is the function of MAST cells in the inflammatory response? What is the function of histamines?
Release histamines at sites of tissue damage
Histamines - cause blood vessels to dilate and become more permeable.
What role do neutrophils and macrophages play in the inflammatory response?
Release cytokines that increase blood flow to the site of infection or injury,
What is pus that accumulates at sites of inflammation?
Fluid that is rich in WBCs and debris from damaged tissue.
What is the purpose of dilating blood vessels and increasing permeability in the inflammatory process?
To increase local blood supply and allow more phagocytes and AMPs to enter tissues.
MAST cells and basohils are similar cells, but what makes them differ?
Basophils reside in blood while MAST cells reside in tissues.
Do invertebrates have an inflammatory response?
NO
Be able to describe the major events of the inflammatory response described in this picture.
DO IT.
- MAST cells release histamines to dilate capillaries and permeate them, macrophages release cytokines to attract neutrophils
- Capillaries widen and become permeable, neutrophils and fluid containing antimicropbial peptides enter the tissue
- Neutrophils digest pathogens and cell debris at site of injury, tissues eventually heals.
What is happening in step 2 of this picture?
- Margination - blood cells slow down and attach to endothelial cells.
- Diapedesis - or extravasation, is the passage of blood cells through intact capillaries, usually during inflammation.
Can the inflammatory response be either local or systemic?
YES
What is a specific systemic inflammatory reponse? What causes this?
Fever
Caused by pyrogens released by macrophages
Can a fever be a good thing?
YES
Fever – believed to not only further stimulate immune system, but help to denature bacterial proteins to decrease bacterial proliferation.
What is sepsis? What is thought to be the phenomenon that cuases this?
A life-threatening condition caused by an overwheling inflammatory response due to an infectious process.
A cytokine storm usually causes this overwhelming inflammatory response
Can inflammation be acute or chronic?
YES
Have a basic understanding of the sepsis continuum.
…
What are the three lymphocytes and what immune response do they tend to? Where do they come from?
They all come from lymphoid stem cells:
T and B cells - adaptive immunity
NK cells - innate immunity
Where do B cells mature? Where do T cells mature?
B cells - mature in the bone marrow
T cells - mature in the thymus
Where are the stem cells that make blood cells located?
Bone marrow
What is immunological memory? What cells contribute to this?
This is an enhanced immune response to a foreign molecule that was encountered previously
T and B cells contribute to this
What do B-cell antigen receptors look like?
Shaped like a Y
What is the significance of the variable regions of the light and heavy chains of the B cell antigen receptors?
These have varying amino acid sequences from one B cell to another that make up the antigen binding site.
What is MHC II and what is its role in antigen presentation?
Major histocompatibility complex II
This is used in our antigen presenting cells as well as infected cells to transport antigen fragments from the inside of the APC to the cells surface (antigen presentation).
MHC II is the molecule that presents the antigen fragment on the surface of APCs.
Describe the 1st property of the adaptive immune response, the B and T cell diversity. How is it that a B and T cell can produce so many different receptor sites? Elaborate?
Through DNA rearrangement or DNA shuffling
Random sites of the gene are chosen to be used vs. being deleted in regards to expression of the receptor as the cell differentiates. This process allows for the many different types of receptors.
Describe the third important important property of the adaptive immune respone: proliferation of B cells and T cells.
Binding of an antigen activates mature lymphocyte to divide rapidly.
This rapid division is known as proliferation, or clonal selection.
Describe the fourth important aspect of the adaptive immune response: immunological memory. What differs between the primary response and the secondary response.
Primary - The first exposure - plasma cells produced, response peaks 10-17 days after exposure. low and slow.
Secondary - second exposure to same antigen - response is of greater magnitude and response can be prolonged due to reservoir of memory cells and rapid response of plasma cells. peaks 2-7 days after exposure.
Describe the differences between MHC I and MHC II. Where are they found? What do they present? What do they activate?
MHC I:
- found on every NUCLEATED cell in the body
- present endogenous antigens like viral fragments or tumor proteins
- antigens presented to cytotoxic T cells
MHC II:
- found on B-cells, macrophages, and other APCs
- Present exogenous antigens such as digested fragments of foreign cells
- present antigen to helper T cells
Describe T helper cell activation.
Accessory protein on helper T cell binds to MHC class II on the APC.
Remains bound while activation occurs.
Activated cell secretes cytokines that stimulate other lymphocytes.
Look at this picture and understand helper T cells role in both cell-mediated and humoral immune response.
- APC engulfs pathogen, degrades it, and presents fragment on MHCII molecule. specific helper T cell binds to it.
- After binding, the APC AND the helper T cell secrete cytokines to activate the helper T cell to prloferate.
- The clonal selection produces more t helper cells that have same receptor for antigen. more cytokines are released by these cells that activate B cells and cytotoxic T cells.
What happens when a cytotoxic T cell responds to signals from T helper cells and binds to a MHC I complex of an infected cell?
It becomes an active killer that secretes proteins (granzymes that break down proteins, or perforins that make pores on surface of cell causing it to lyse) to destroy the infected cell.
What aids in the activation of B cells for the humoral response to occur?
cytokines
antigen binding to helper T cells
What are the 3 ways that antibodies function to dispose of pathogen?
- neutralization - antibodies bind to antigens on surface of pathogen (virus or toxin, something smaller than bacteria) blocking its ability to bind to a host cell.
- Opsonization - binding of antibodies to antigens on surface of bacteria promotes phagocytosis.
- Activation of complement system - antibodies bind to surface antigen of pathogen, complement system is activated, membrane attack complex is created and forms pores in cells membrane which lyses the cell.
Look at this overview diagram of the humoral and cell-mediated adaptive immune responses and understand it.
DO IT. P. 965.
How do allergies develop?
After the first exposure to the allergen, igE that has been produced attached to MAST cells.
The next exposure to allergen facilitates binding of allergen to MAST cell associated IgE molecules.
This causes the release of histamine which causes symptoms of hay fever.
Have a basic understanding of this graph that shows the progress of untreated HIV infection.
- Blue line - Concentration rapidly increases for first 6 months, drops after most of HIV DNA is integrated into helper T cells and is replicationg.
- Red line - antibodies are being performed but aren’t enough to fend off infection due to antigenic variation and latency.
- Black line - T cells are dying off as virus infections and kills them
