Week 11 Review Flashcards
What are the main differences between innate and adaptive/acquired immunity?
Innate:
Born with
Not specific
No memory
First and second-line defense
Adaptive:
After a breach of innate
Specific
Memory
Third line of defense
What are the first lines of defense? What are physical, and chemical barriers? What is the role of normal microbiota?
Physical barriers:
- Intact skin
- Mucous membranes
- Vomiting, diarrhea
Chemical barriers:
- Secretions (mucus, sebum, sweat, tears, earwax, saliva)
Normal microbiota: outcompete pathogens
Compare and contrast granulocytes and agranulocytes. Give examples.
Granulocytes:
Granular appearance under microscope
Neutrophils: granules have lytic enzymes, kill bacteria
Basophils: inflammation
Eosinophils: excrete toxic compounds, allergies
Agranulocytes:
Smooth appearance under the microscope
Monocytes (macrophages dendritic cells)
Lymphocytes (B/T cells) - role in adaptive
What are the second lines of defense? Describe each form.
Phagocytosis: ingestion of cells/particles by phagocytes (Leukocyte/WBC)
- Granulocytes and agranulocytes
Inflammation: redness, pain, heat, swelling
Fevers: induced by complement, a system of proteins that complement the immune system
- Cytolysis (cell lysis)
- Inflammation
- Phagocytosis
Antimicrobial substances
- Interferons (IFNs): antiviral proteins that disrupt viral replication
- Antimicrobial proteins (AMPs): inhibit cell wall synthesis; form pores in plasma membrane; destroy DNA and RNA
What is the dual nature of the third line of defense? What are the differences between humoral and cell-mediated immunity?
Adaptive (acquired) immunity
Humoral:
- Free antibodies made by B cells
- Controls circulating pathogens
Cellular:
- T cells
- Controls intracellular pathogens
What is the general structure of an antibody?
Y shaped
2 heavy chains, 2 light chains
2 antigen-binding sites
What are the different types of antibodies? How do they differ in terms of structure, function, and location? What is the most common Ig? Which can be cell-bound?
IgG (most common)
Structure: monomer
Function: enhance phagocytosis, neutralize toxins/viruses, protect fetus/newborn
Location: blood, lymph, intestine
IgM
Structure: pentamer
Function: effective against microorganisms/agglutinating antigens, first antibodies produced in response to infection
Location: blood, lymph, B cell surface (monomer)
IgA
Structure: dimer
Function: localized protection on mucosal surfaces
Location: secretions (tears, milk, blood)
IgD
Structure: monomer
Function: serum function not known, presence on B cells functions in initiation of immune response
Location: B cell surface, blood, lymph
IgE
Structure: monomer
Function: allergic reactions, possibly lysis of parasitic worms
Location: bound to mast and basophil cells
Describe the effects of antibody-binding antigens. Which cells produce antibodies?
Ig on the B cell surface recognizes and binds Ag (extracellular antigen).
Ag internalized and “processed.” Part of the antigen combines with MHC class II
MHC II-Ag fragment presented on the cell surface of B cell
TCR (T cell receptor) recognizes and binds MHC class II-Ag on B cell surface
B cells are activated by cytokines which induce clonal expansion. Some become antibody-secreting plasma cells
Which type of B cells secrete antibodies?
MHC class II
What are the other results of antigen-binding antibodies? How does each method work?
Agglutination: antigens clump together
Opsonization: coated antigen cause ingestion and lysis by phagocytes
Neutralization: IgG antibodies inactivate microbes by blocking attachment to the host
Activation of complement: causes inflammation and cell lysis
Antibody-dependent cell-mediated immunity:
- Ab binds parasite
- Eosinophil/macrophages recognize and bind Fc of Ab
- Eosinophil and macrophages secrete cytotoxic cytokines, lytic and perforin (pore-forming) enzymes
What are the two main types of TH and how are they classified? What different antigens/MHCs does each bind?
Classification based on clusters of differentiation (CD)
T helper cells (TH)
- CD4
- Bind MHC Class II on B cell and APC (antigen-presenting cell)
Cytotoxic T cells (TC)
- CD8
- Bind MHC Class I on APC
MHC I + CD8= intracellular MHC II+ CD4= extracellular
How are TC and TH activated?
TC:
APC presents MHC class I/Antigen complex
The complex binds TCR on CTL
TC releases perforin, a pore-forming protein
Target cell lysed
TH:
APC ingests microbe
Antigen processed/presented on MHC II
TCR binds to MHCII-antigen complex
APC secretes a costimulatory molecule
TH secretes cytokines and proliferates also making memory cells
What are the different types of TH cells? What cytokines do they produce and what is their method of action?
TH1: IFN-y; stimulate cell-mediated immunity, activate macrophages
TH2: IL-4; allergic reactions, parasitic reactions
TH17: IL_17, activate innate immunity; respond to extracellular bacteria
How is a primary response different from a secondary response?
Primary response:
- Innate
- first contact of the immune system with an infectious agent
- slow and weak
Secondary response:
- Adaptive
- responding to a previously encountered antigen
- quicker and more robust
What are the different types of adaptive immunity? Naturally acquired and artificially acquired? Passive and active?
Naturally acquired:
- Active: antigens enter the body naturally; body induces antibodies and specialized lymphocytes
- Passive: antibodies pass from mother to fetus via placenta or to infant via the mother’s milk
Artificially acquired
- Active: antigens are introduced in vaccines; body produces antibodies and specialized lymphocytes
- Passive: preformed antibodies in immune serum are introduced by injection
