Specific Host Defenses Flashcards
Chapter 17
What is Specificity?
Recognizes specific foreign substance
What is Non-self regarding cells?
Foreign
What is self regarding cells?
Body’s cells
What cells are foreign? (4)
- bacteria
- viruses
- pollen
- transplanted tissues
How does your immune system obtain memory of specific antigens/infection?
After recovering from a specific infection, you are immune to it when exposed again (memory)
What are antigens (Ag)?
Substance that stimulates an immune response
What mediates Specific Acquired Immunity?
Lymphocytes
What are the two lymphocytes?
- T cells
- B cells
What type of immunity do T cells provide?
Cellular Immunity
Where do T Cells Mature?
Thymus
What type of immunity do B Cells provide?
Humoral Immunity
Where do B Cells mature?
Bone Marrow
Where do T Cells originate from?
Bone Marrow
Where do B Cells originate from?
Bone Marrow
What do B Cells do?
Produce ANTIBODIES that recognize and bind to Ag
What do T Cells do?
Have cell surface receptor (TCR) that recognizes Ag on surface of TARGET CELL
What is acquired immunity?
Protection developed over time against a specific Ag after injection/vaccination
What are the 4 ways immunity can occur?
- naturally
- artificially
- actively
- passively
What is Naturally Acquired Active Immunity?
Immunity acquired when person encounters the pathogen naturally
What is Naturally Acquired Passive Immunity?
Natural transfer of preformed Ab from mother to fetus/infant
What is Artificially Acquired Active Immunity?
Immunity acquired after vaccination against a specific infectious agent
What is Artificially Acquired Passive Immunity?
Immunity acquired after injection of preformed Ab
What is involved in the humoral immune system? (3)
- B lymphocytes
- antibody mediated
- effective vs. extracellular
What is involved in the cell mediated immune system? (3)
- T lymphocytes
- mediated by cell-cell interactions
- effective vs. intracellular
What are antigens?
Substance that elicits an immune response
Describe antigens (3):
- large
- usually a protein
- can be polysaccharide, nucleoprotein, or glycolipid
Which type of antigens are not good? (2)
- lipids
- nucleoacid
What different Ag cover the surface of pathogens? (6)
- pili
- cell wall
- capsules
- outer membrane proteins
- flagella
- toxins
What is Epitope?
Section on the Ag that Abs bind to
What produces antibodies?
B Cells (aka Plasma Cells)
Where are antibodies found? (2)
- surface of B cells as Ag receptor
- secreted into serum, lymph, and fluids surrounding tissue
What do Ab’s produced by ONE plasma cell do?
Recognizes only a single portion of an Ag and binds
What are two other names for antibodies?
- Gamma Globulins
- Immunoglobulins
What shape do Ab’s have?
Y shaped molecule
Why is it an Ab’s shape beneficial to it?
Flexible Adapter
Describe Antibodies (2)
- proteins
- 4 chains
Describe the 4 chains of Ab’s:
- 2 Identical Heavy Chains (Hc)
- 2 Identical Light Chains (Lc)
What holds chains in Antibodies together?
Disulfide bonds
What do each Hc and Lc contain?
1 Variable region (V)
What does each Lc contain?
1 Constant region
What does each Hc contain?
3 or 4 Constant regions
What do the variable regions of Hc/Lc make up?
Ag binding site
How many antigen binding sites are there on one antibody?
2 (identical)
What does Fab stand for?
Fragment antigen binding
What do the Ch regions determine?
The Ab (Ig) class
What are the five classes of Ig?
- IgG
- IgM
- IgA
- IgD
- IgE
Describe IgG (5)
- monomers (individual Y shaped molecules)
- Secondary Immune response
- Can enter tissues + cross placenta
- Activate the Classical Complement Pathway
- Act as an Opsonin
What Ig makes up 80% of Antibodies found in serum?
IgG
What are IgG’s effective against? (3)
- bacteria
- extracellular viruses
- bacterial toxins
Describe IgM (5)
- First Ab produced in primary immune response
- M = Macroglobulin (Large)
- 10 binding sites
- Activates Classical Complement Pathway
- Valuable in diagnosing Disease
How long is the half- life of IgG?
~23 days
Which Ab’s half life is ~5-10 days?
IgM
What is IgM important for?
Diagnosis of disease
What holds IgM monomers together?
J chain
What holds 5 IgM monomers together?
J chain
Describe IgA (4)
- SECRETORY Abs
- Found in mucous membranes & secretions
- Can be monomer, but mainly DIMER
- first line of defense of specific acquire immune system
What Ig makes up 10-15% of Abs?
IgA
How long is IgA’s half-life?
~6 days
How many binding sites does a dimer of IgA have?
4
Describe IgD (3)
- found on surface of newly matured B cells
- act as Ag receptor for B cells
- unknown functions
What % of Ab’s does IgD make up?
0.2%
Which Ig has a half-life of ~3 days?
IgD
Describe IgE (3)
- found bound to mast cells & basophils
- defense against parasitic worms
- causes allergic response by recognizing allergens
What Ig makes up 0.002% of Ab’s?
IgE
How does IgE bind to cells?
By Fc region to specific cell surface receptors
What happens when an Ag binds to a IgE?
Immediate degranulation of mast cells & basophils
What happens when IgE causes mast cells & basophils to degranulate? (2)
- cytoplasmic granules’ contents (histamine & serotonin) are released
- (histamine) causes increased capillary permeability (vasodilation)
Where do B cells in birds mature in?
Bursa of Fabricius
Where do B cells in animals mature in?
Bone Marrow
What happens in humoral immunity? (4)
- B cells exposed to an extracellular Ag
- B cells mature
- B cells migrate to secondary lymphoid tissue to develop further
- B cells bind with the appropriate Ag
When in humoral immunity do B cells selection of Ag receptors occur?
During maturation in bone marrow/bursa of fabricius
What do B cells have on their surface? (2)
- IgM
- IgD
What are examples of secondary lymphoid tissue? (2)
- lymph nodes
- spleen
Where do B cells encounter Ags?
In the secondary lymphoid tissue
What occurs when B cells bind with Ags?
Stimulation of proliferation of said B cell (Clonal Selection)
What happens during Clonal Selection?
B cells can change into Plasma Cells or Memory Cells
Which Cell aids B Cells in Clonal Selection?
Helper T Cells
(T/F) All Antibodies produced by one B Cell have different Ag Specificity
False, They all recognize the same epitope
What cell rearranges a B Cell’s Ig genes during development?
The B Cell itself
What happens in Cell Mediated Immunity? (
- T Cells mature in thymus gland
- T Cells migrate to secondary lymphoid tissue
- T Cell encounters Ag and activates
What do T Lymphocytes arise from?
A common precursor cell in the bone marrow
Where do T Cells mature in?
Thymus Gland
What do T Cells mainly fight?
Intracellular Pathogens
Where do T Cells encounter the Ag?
Secondary Lymphoid Tissue
What do T Cells activate into?
1 of various types of effector T Cells
If a T Cell with an Ag specific TCR encounters an Ag…
Proliferation & activation of those Ag Specific T Cells
How do T Cells recognize antigenss?
When Antigen Presenting Cells (APC) process antigens and present it to them
What are the different types of T Cells? (
- Helper T Cells (CD4+)
- Cytotoxic T Cells (CD8+)
What do Helper T Cells do?
Help B Cells & other T Cells to react
What nickname do Helper T Cells have?
Commander in Chief
What do Cytotoxic T Cells do?
Killer Cells
What does CD stand for?
Clusters of Differentiation
What activates T Cells?
Ag/MHC complex + Professional APC signal
What are examples of Professional APCs? (3)
- Dendritic Cells
- B Cells
- Macrophages
How do B Cells & Macrophages become Professional APCs?
Activated by Ag
What are the types of MHC Ags? (2)
- Class I
- Class II
Describe Class I MHC Ags
All cells (except RBCs, sperm, ovum, cornea)
Describe Class II MHC Ags
Activated macrophages, mature B cells, some T Cells
What do Class I cells do? (2)
- mark cells as “self”
- directly activates CD8+ cells
What do Class II Cells do? (2)
- Recognition of “self”
- required for CD4+ cells to interact with B Cells & Macrophages
What do T Cells recognize?
Ag bound to cell surface
What holds Antigens onto cell surfaces?
Cell Surface Protein (Marker)
What is a Marker
Major Histocompatability Complex (MHC)
Describe MHC molecules (2)
- unique to each person
- tell immune system which cells are “self” and “non-self”
(T/F) T Cells see antigens that are not within MHC molecules on a cell’s surface
False
What is another name for Helper T Cells?
CD4+ Cells
Describe Helper T Cells (2)
- recognize antigens on macrophages/APCs
- activate macrophages
What do activated T Cells do?
Proliferate and secrete cytokines
What do activated T Cells do?
Become activated helper T Cells that activate other cells (B, T, macrophages). Some become memory cells.
What is another name for Cytotoxic T Cells?
CD8+ Cells
What do CD8+ Cells do?
- when activated, they recognize and kill target cells
- produce perforin (lyses cell)
What are Cytotoxic T Cells precursors to?
Cytotoxic T Lymphocytes (real killers)
How do Cytotoxin T Cells become activated?
By cytokines from Th cells
After perforin destroys the cell, what happens?
Granzymes enter and induce apoptosis
What do CD8+ T cells recognize?
Antigen presented in association with MHC class I molecules
What is a primary immune response?
First encounter with a specific antigen
What is a primary immune response?
First encounter with a specific antigen
What occurs in primary immune response? (2)
- IgM first to produce, then IgG
- Memory Cells are produced
What is a secondary immune response?
Repeat encounter with same antigen (memory)
What happens in secondary immune response? (3)
- stimulation of memory cells
- increased levels of IgG & IgM
- Stronger, faster, more specific response
What measure the intensity of the antibody mediated immune response?
Antibody titer
What does the antibody titer check for?
The amount of antibodies in serum
