Immunology Exam 3 Flashcards
Exam Study (26 cards)
What is an Epitope
The smallest subunit of antigens
Define linear epitope
Exist within the Amino acids sequence. Even if structure is denatured. 8-15 residues long
Define discontinuous epitope:
Not in the primary sequence shapes formed by secondary and tertiary structures
( other chains coming together)
Define immunodominance:
Some epitopes are better at creating an immunolog response then other
Can be animal specific but usually specific specific.
Describe the characteristics of a molecule that determine antigenicity
1 of 3
Immune system recognizes small portion of macromolecules ( not the whole structure)
- Discrimination between self and nonself
- Occurs by recognition of molecular shape
Describe the characteristics of a molecule that determine antigenicity
2 of 3
Antigen is molecular shpat that can be recognized by antibody or lymphocytes
Describe the characteristics of a molecule that determine antigenicity
3 of 3
An epitope is the smallest subunit of an antigen.
What is the difference between an antigen and an immunogen
- Antigen: molecular shpate that can be recognized by antibodies/ lymphocytes surface receptors
- Immunogenic: if it stimulates an acquired immune response by itself
- Immunogens are antigenic but not all antigens are immunogenic has to follow all the characterisics of an antigen
- Size is greater the 1,000 DA
- Lots of peptides.. if smaller will be recognized but no immune response will be caused
- Complex
- Greater vaiety of epitopes
- Knows self from non self
- Ridity
- Epitopes must maintain shape to generate a response
- Degrabadility:
- Large molecures must be broken down into individual epitopes to initiate response
- Antigenicity : Proteins > carb> lipids and nucleic acids > metals and plastics
Why does cross-reactivity occur?
- Very simialru epitopes but are found on very dissimilar molecules or on evolutionaily similar molecules
- Antibodies formed in an immune response to one immunogen may recognize epitopes on another molecule
- Cross- immunognes: same or similar epitope found in dissimilar molecules can afford protective immunity to one when primary exposure is to the other: human meslase virus vacc for canian distemper
Vocabulary:
Co-expression:
Mult genes being expressed at the same time
Endogenous antigen:
Antigen coming within presenting cell ( self) exogenous antigen
What is the genetic organization of the
MHC genes. (generally)
- MHC 1: 3 genes that are coexpressed, with 2 allels per individual ( 2 copies of each)
- Could have up to 6 different genes on one cell surface
- Inbreding lowers diversity of MHC1 genes
- Pseudogense
- MCH2: 17 genes, highly polymorphic – several coex[ressed genes in an individual many alleles in the population
- Has proteasome TAP 1, 2
- MHC3:
What are the functions of class I vs. class II MHC receptors and their cellular distributions
- MCH 1: found on all nucleated cells, highly expressed on most cell of immune system, CD8
- MHC 2: found on APC: Dendritic cell, B lymphocytes, monocytes
How is MHC polymorphism important for individuals and populations.
- Polymorphism: having the ability to binding different peptide forms on the MHC molecule.
- This leads to varying difference of sickness/reaction to pathogen.
- In a heard setting if one person/animal got sick due to polymorphism other people/animals would be most likely about to recognize and bind the pathogen there fore not getting sick. Then the disease wouldn’t spread through the heardà
- Therefore polymorphism is very important!
What is the distribution, life cycle,
and functions of dendritic cells
- Found under skin, mucosal surface, lymphnoes
- NOT in brain, eyes and testies
- Starts in the bone marrow à monocoyie or lymphoid à if they don’t bind to an antigen will die within 4-5 days
- Immature DC ( one not bound to an antigen before)
- Expresses HIGH durface Fc receptors ( if bound to an antibodie), Mannose and chemokine receptors, TLRS 2 & 4, intracellular MHC 2
- LOW: surface MHC 2, costimulatory Il12
- Mature: ( once bound to an antigen) boosts antigen presentation functions
- Expresses HIGH: MHC 2 surface receptors, costimulatory IL-12
- Migrate to secondary lymphoid organs to present to T cells
- Cells are polarized: have specialized functions
- Extra vs intra
- Humoral ( extra cellular) vs. cell mediated ( intracellular)
Vocabulary:
Endogenous antigen:
Antigen coming within presenting cell ( self) exogenous antigen
Vocabulary:
Co-expression:
Mult genes being expressed at the same time
What is cross-priming?
- If an peptide escapes from an endosome vesicle it would be in the cytosol à go through proteasome à bind to class I and become express on MHC 1
What are the inherited determinants of disease resistance and susceptibility related to antigen presentation?
- TAP ( transport antigen protein) and MHC: determines ones potential for immune response
- However whether exogenous or endogenous antigen NEEDS to be bound to an MHC molecule to trigger an immune response
- Distinguish primary from secondary lymphoid tissues
- Which tissues fall into each category.
Primary:
Develop early in fetal life
Removal causes loss of lymphocytes and lymphocyte function à immune impaired
Sites of foregin antigen independent lymphocytes development and differentiation
Secondary:
Develop later in gestation
Removal will little effect on immune responses
Foregin antigen dependent lymphocyte development and differentiation
Where lymphocytes function to create an antigen- specific imuune response
Be able to distinguish primary from secondary lymphoid tissues and know which tissues fall into each category.
- Primary:
- Develop early in fetal life
- Removal causes loss of lymphocytes and lymphocyte function à immune impaired
- Sites of foregin antigen independent lymphocytes development and differentiation
- Secondary:
- Develop later in gestation
- Removal will little effect on immune responses
- Foregin antigen dependent lymphocyte development and differentiation
- Where lymphocytes function to create an antigen- specific imuune response
Describe the movements of a lymphocyte
from birth to death.
- Start in the bone marrow à travel through out the body in blood, vessels and lymphatic
- Cells have adhesions protein which tells them which target to go to
- Different adhesion protein is expressed depending on stage of development
- Cells die within 3-4 days in the tissue if not exposed to an antigen
(Side note: Global response directed at antigen encountered locally is from)
- Circulation of lymphocytes
- Secretion of antibodies (from plasmid cells) à create one characteristic of specific immunity
Describe two main phases of lymphocyte development
- What is happening
- Where these events occur.
- Part one: foreign antigen – independent phase
- Generation of diversity
- Replication and progressive differentiation à NEW surface proteins
- Random reorganization of antigen binding sites of surface receptors ( either BCR or TCR)
- This creates generate antigen binding diversity
- Cells are educated à removed if bind to self
- Develops tolerance
- Part two: foreign antigen- dependent phase
- Clonal selection
- Replication and further differentiation into effector cells
- Requires antigen recognition of T h cells
Explain the functionally important cell-surface receptors of B and T lymphocytes.
B- cells
- BCR: interaction with antigen
- igM monomer à same antigen binding specificity as the antibodies that b cell is capable of producitn
- Rectors for interleukins: mediate B cell response
- IL 2R, 4R, TFG-bR, IFN-yr
- MHC 2: B cell function in capture and resentation of EXOGENOUS ANTIGENS
T-cells
- TCR: is a dimer may be a/b or y/d
- CD3: protein complex required for signal transfuction via TCR
- All cells have CD3
- CD4: specific marker of T helper cells à MHC 2 molecules and HIV, exogenous
- CD8: Specific Cytolytic T lymph à MHC 1, nucleated cells endogenous
- Interleukins: mediate T cell response
Know the 3 types of antigen-sensitive lymphocytes
&
The effector cell phenotypes each one obtains when activated.
- Tc cell
- TH cell
- Bcell
