FHD - immune response

contains FHD topics - B cells and antibodies, T cells and antibodies, introduction to immunity

which cells can present within the MHC class I context

All cells except RBCs

What do suppressor T cells do

Terminate immune cell activity to suppress immune response

How do suppressor T cells carry out their function

secrete signalling molecules that bind to receptors on other immune cells to terminate their activity

What is a CD marker 

a cell surface molecule that is used to differentiate between different leukocytes subtypes 

Which CD marker do T helper cells express

CD4

Which CD marker do cytotoxic T cells express

CD8

what is endogenous antigen presentation used for

to deal with Intracellular infections

When does sampling occur in the endogenous antigen presentation pathway 

continuously, regardless of if there is an infection or not 

what is the first stage of the endogenous pathway of antigen presentation 

Cytosolic proteins are degraded by the proteasome complex, producing peptides 

what occurs to the peptides produced from the degraded cytosolic proteins in the endogenous antigen presentation pathway 

they associate with TAP (transporter associated with antigen processing)

What occurs to the peptides associated with TAP (endogenous pathway)

They are transloacted into the RER

what occurs in the RER (endogenous pathway)

peptides associated with TAP bind to the class I MHC molecule

What is exogenous antigen presentation used for

extracelluar infections

which MHC class is exogenous antigen presentation involved with 

MHC class II

Which cells are capable of interaction with MHC class II (in terms of MHC presentation)

macrophages and B cells

How are peptide fragments produced in exogenous antigen presentation 

extracellular antigens are phagocytosed and desgraded in endosomes to produce peptide fragments

where are MHC II molecules prepared

in the Golgi

what is CLIP

Class II associated invariant chain peptide

Where is clip found 

on the binding groove of MHC class II molecules 

What occurs to CLIP to uncover the binding groove on MHC II

it is proteolytically degraded within the endosome

what binds to the MHC II binding groove

the antigen peptide

what occurs to the Antigen peptide MHC class II complex

it is displayed on the surface of the APC

what does MHC stand for 

major histocompatabilty complex 

what are MHC Molecules

proteins on the surface of cells that display antigen fragments to T cells 

What encodes for MHC molecules in humans

HLA gene complexes

What T cell responds to class I MHC

Cytotoxic T cells

What T cell responds to class II MHC

Helper T cells

what do helper T cells do when activated in response to a class II MHC

secret cytokines to activate CD8

In what region of the T cell receptor is there most diversity

The V region

what two subunits are T cell receptors composed of

an alpha and beta subunit

What are the beta and alpha subunits of T cell receptors composed of

A random combination of V, J, C (and D if beta) genomic regions

Does affinity or class switching occur in T cell receptors during immune response

no 

what act as T cell receptor co receptor in MHC interactions 

CD4 and CD8

Which cell (T or B) undergoes affinity maturation and what does it do 

B cells, it mutates their receptor 

What are PAMPs

common molecule patterns found on pathogens 

what are pattern recognition receptors, and what do they do 

Proteins found on or inside immune cells that detect PAMPs

What occurs when a pattern recognition receptors binds to a PAMP

They activate signalling pathways to trigger immune response 

do pattern recognition receptors exhibit molecular memory or adaptive ability during immune response 

no 

how are pattern recognition receptors coded (don’t overcomplicate this answer)

Entirely germ line coded

Which MHC class can phagocytes process

MHC class II

what are NK cells

natural killer cells

What do NK cells do

process receptors that bind to the Fc domain of antibodies, and arm them to attach to a specific antigen target 

what is a brief outline of the structure of an antibody

two heavy chains and two light chains

in surface antibodies what bonding is found between the two heavy chains

disulfide bridges

which part of the antibodies are identical

the heavy chains

what is the Fv domain 

the antigen binding site 

what is the epitope

the part of the antigen that the antibody binds to

what do the antibodies of naive B cell contain to anchor the BCR to its surface

an additional transmembrane domain

in the format of an antibody containing an additional transmembrane domain that anchors it to the surface of B cells, what is it known as

 a B cell receptor (BCR)

how is the BCR activated (2 ways)

by antigen cross linking and cytokine mediated stimulation (by T helper cells)

what occurs when the B cell is mature, that allows the secretion of identical soluble antibodies 

gene rearrangements 

what determine the antibody class/ isotype

the heavy chains

what does the antibody class/ isotype determine

which immune system partner the antibody molecule works with 

what are the three categories antibody classes fit into

monomers, dimers and pentamers

which antibody classes are monomers

IgG, IgD and IgE

where are IgG antibodies found

circulating the blood

where are IgD antibodies found

on the surface of B cells

where are IgE antibodies found

mucosal surfaces

which antibody class is a dimer

IgA

where is the IgA antibody class found

mucosal surfaces

which antibody class is a pentamer

IgM

where are IgM antibodies found (in response to)

allergy and asthma response

what is a brief overview of the structure of IgM

5 molecules linked via a J chain

how many binding sites are on IgM

10

what is a brief overview of the structure of IgA

two antibody molecules are linked together via a J chain and a secretory piece 

what is the purpose of the secretory piece in IgA

to protect from proteolysis and facilitate secretion across mucus membranes

what is a brief outline of the structure of Fab fragments

one light chain and one heavy chain

what is the antibody valence of a Fab fragment

1

what is the antigen valence and affinity of a fab fragment

1, with intrinsic affinity

what is antibody valence

the number of antigen binding sites on an antibody

what is meant by antigen valence

the number of epitopes on an antigen

what is the antibody valence of IgA

1 or 2

what is the antibody valence of IgM

5

what is the antibody valence of IgG, IgE and IgD

1

what is avidity

functional affinity, where multiple binding sites come together for the antigen to bind to

which antibodies have intrinsic affinity

fab fragments and univalent IgG

which antibodies have avidity

bivalent IgG and IgM

what is V in terms of antibody structure

the variable segment

what is D in terms of antibody structure 

the diversity segment

what is J in terms of antibody structure

the joining segment

what is C in terms of antibody structure

the constant segment

What does the light chain consist of (in terms of different segments)

V, J, and C

what is the purpose of somatic recombination in antibodies 

to allow B cells to differentiate and become immunocompetent 

What are the three things required for somatic recombination in antibodies 

Recombination signal sequence, recombination activation enzymes, and epigenetic changes to the DNA structure 

what does the C region control within the heavy chain

the class of antibody that is produced

what is class switching

when changes occur to the constant region that alters an antibody class

What is the constant region recognised by

the Fc receptor

Where is the Fc receptor found 

On leukocytes

What is the purpose of Fc receptors

to help identify pathogens that have been identified by antibodies

When is the B cell said to be antigenically committed

once gene rearrangements are complete

what is affinity maturation

when additional changes in the structure of an antibody occurs to improve antigen binding affinity 

when does affinity maturation occur

when a B cells encounters an antigen for the first time

What is clonal expansion

the activation of cells leading to the production of clones with the same antigen binding capability 

What is Anergy

When there is insufficient activation energy - can result in death via apoptosis

when does anergy occur (in terms of cell activation)

if only one binding event occurs

What are the two activation events that must occur for clonal expansion to take place

antigen binding, and stimulation by growth factors

How does agglutination occur

when an antibody binds to multiple antigens, forming cross links

What antibody classes do naive B cells produce in the primary immune response 

IgD and IgM

in primary immune response are IgD and IgM specific or nonspecific to the antigen

specific 

what is the affinity and avidity of IgD and IgM in the primary response

low affinity but high avidity due to IgM