B-lymphocytes and Antibody production

why is it important that B-cells are semi-pro APCs?

BCRs need to present antigen proteins to T-helper cells so that T-helper cells can provide cytokine help for B-cell to make antibodies and memory B-cells

the B-cell receptor and antibody recognize the same...

antigen

what do B-cells becomes after clonal expansion and what can they do?

plasma cells and make antibodies

what happens if a B-lymphocyte becomes infected?

present microbial protein antigens to CTLs

what are the processes in which the antibody help destroy extracellular pathogens?

1. activate complement cascade

2. opsonize pathogens for phagocytosis

how can antibodies help NK cells?

antibodies bind antigens on the surface of target cells and NK Fc receptors recognize cell-bound antibodies

why would we want to detect a humoral immune response in an animal?

1. determine if animal has been exposed to pathogen

2. if animal was able to respond to a vaccine

3. help with diagnosis in pathogen of interest

how can we assess a humoral immune response in an animal?

detect antibody to antigen of interest in serum

what else can we assess besides serum for a humoral immune response?

CSF and joint fluid

what is required for B-cells to be able to make protein antigens?

they need cytokine help from T-helper cells to make antibody and memory B-cells specific to protein antigens

what type of antigen do the majority of B-cells recognize?

protein antigen

what would an example of non-protein antigens that some B-cell receptors could recognize?

carbohydrates and lipid molecules

what would an example be of a BCR recognizing a non-protein antigen?

epitopes on LPS molecules of gram negative bacteria

why is the response limited for B-cells that respond to non-protein antigens?

they do not receive cytokine help from T-helper cells meaning no memory cells will be produced and no memory response for future

what is the only antibody plasma cells can make in response to non-protein antigens?

IgM

even though the response to non-proteins is limited...

the antibody produced will still be SPECIFIC to the antigen recognized by the BCR

what can occur when B-cells have BCRs for protein antigens?

1. memory B-cells generated

2. antibody class switching

3. antibody affinity maturation

4. plasma cells long-lived

what are the results of B-cells with BCRs for non-protein antigens?

1. no memory B-cells generated

2. only IgM made

4. plasma cells are short-lived

describe the antigen of non-proteins

simple, repeating polymers

what do we mean when we say plasma cells are terminally differentiated cells?

parent B-cells clonal expand, not the plasma cells; the plasma cells make the antibody

why is the response in adaptive humoral immunity polyclonal?

• microbe has multiple antigens/epitopes

• different B-cells with their unique BCRs will need to be employed to attack different antigen types

what does the class of antibody the plasma cell makes depend on?

the type of cytokine help it gets from Th-2 and Th-2 cells

what do cytokines from T-helper 1 cells promote?

promote activation of effector immune cells and helps with cell-mediated immune responses

what is an example of an antibody produced by Th-1 cell cytokines?

opsonizing antibody that will help phagocytic cells target microbes

cytokines from which T-helper cell involve other cells?

Th-1

cytokines from which T-helper cell will not involve other cells?

Th-2

what do cytokines from Th-2 cells promote?

neutralizing antibody

what is an example of a neutralizing antibody?

neutralizing antibody binds spike protein of covid virus and now the virus cannot enter the host cells

what can cytokines from T-helper cells allow for?

antibody class switching

what is required for antibody class-switching?

can only happen if B-cell has BCR for protein

what remains the same during antibody class-switching?

Fab region

what changes during antibody class switching?

Fc

what does the Fc portion determine in the antibody?

the class of antibody

what happens to the B-cell during antibody switching?

B-cell receives a signal from cytokine to make different plasma cells to make the different classes of antibodies

what antibody is typically made first in a primary response?

IgM

how many binding sites does IgM have?

10

what is the second antibody typically made during a primary response?

IgG

how many binding sites does IgG have?

2

compare memory B and T cells to naive B and T cells

memory cells are long lived and activated much more quickly

how long does the primary adaptive immune response take to detect?

7-10 days

how long does the memory adaptive immune response take to detect?

1-2 days

what do we detect in a serology test?

antigen-specific antibody in serum of blood; we are looking for a humoral adaptive immune response

what does antibody affinity maturation require?

requires cytokine help from Th-cells

what is the key feature of antibody response to protein antigens?

progressive increase in the affinity of the antibody

affinity

strength of antibody binding to antigen

what will we use in the lab as a reagant for a specific immune test?

polyclonal antibody produciton

what is polyclonal antibody production in the lab mean?

can make antibodies from Fc region of other species

why would we immunize an animal several times over several weeks during polyclonal antibody production in lab?

we want robust B-cell antibody response to different epitopes of the antigen

monoclonal antibodies are...

from a single B-cell clone and ALWAYS made in lab

how do we make monoclonal antibodies?

fuse a plasma cell that makes the antibody to one epitope with a cancer B cell so that the new cell will live forever and continue to make antibody

how are glycoproteins separated during SPE?

size and charge of the immunoglobulins

what fluids can be used for SPE?

1. serum (blood clotting factors removed)

2. joint fluid

3. CFS

4. colostrum

where will immunoglobulins migrate towards during SPE?

negative cathode

where are most antibodies located on an SPE?

the gamma globulin fraction

gammaglobulin

antibody

what portion of the antibody binds the antigen?

Fab

which portion of the antibody is responsible for the biological activity?

Fc region

what does the class of antibody refer to?

Fc part of antibody molecule

phagocytic cells have surface receptors for which part of the antibody?

Fc region

where is IgG mainly located in the body?

mainly in the serum of blood

when is IgG made in the immune response?

later, it is the main antibody of memory response

IgG leaves the blood...

easily

what are the functions of IgG?

1. binds pathogens and toxins

2. binds phagocytes via Fc receptors (opsonization)

3. complement activation and destruction of microbe

4. help NK cells kill antibody IgG host cells

which antibody class will be in highest concentration in colostrum in most mammals?

IgG

what does the pentameric nature of IgM allow for?

bind strongly to microbes and large, complex antigens due to multiple binding sites making it good at neutralizing viruses

what is IgM good at doing to the antigen?

aggregating/agglutinating

where is IgM located in the body?

confined to blood and lymph due to large size

what is the first Ig class made in a primary immune response?

IgM

what would a high level of IgM in a serology indicate?

may be an indication to a recent primary exposure to the antigen

why is IgM not considered an opsonizing antibody?

do not have Fc receptor on phagocytes for IgM

what antibody can the complement bind?

IgM

where would we find the monomeric form of IgA in the body?

serum

where would we find the dimeric form of IgA in the body?

mucosal surfaces

what are the functions of IgA?

extremely important in mucosal transport and protection to prevent viruses and bacteria binding to epithelial surfaces

besides the mucosal surfaces where can IgA be found?

tears, saliva, and bile

why is the secretory protein of IgA important?

prevents it from being degraded by proteases in the intestine

what antibody is dominant in milk?

IgA

what is IgE responsible for?

1. adaptive immunity to parasitic worms

2. type-1 hypersensititives

what cell produces IgE in reaction to an allergen?

B-cell

how do IgE bind to mast cells?

via Fc region since mast cells have Fc receptor for IgE

what part of the antibody molecule binds the mast cell?

Fc region

what part of the antibody molecule binds the allergen?

Fab region

what is the main class of antibody produced in a memory response?

IgG

C1 complement protein can bind Fc region of these classes of antibody

IgM and IgG

what is the best antibody for aggregation of antigens?

IgM

what are good neutralizing antibodies?

IgM and IgG

when we say goat anti-dog IgG what does this mean?

IgG antigen from dog was injected into a goat and the goat's plasma cells are making antibodies against the dog's IgG

why would we ever want to make an antibody against another antibody?

to use as a reagent in immundiagnositic tests

when we inject the lepto antigen into a dog's serum, what are we testing for?

that the antibody binds to the lepto antigen

why would we add a reagant antibody when testing the dog for the lepto antibody?

we cannot visualize antibody in serum binding to antigen of interest, we need to tag with an enzyme and add substrate to see (color change)

if the dog had IgG to lepto in its serum, what would we see?

antibody will bind the lepto antigen in the test

A biotech company is marketing a new test and the primary reagent in the test is rabbit anti-cat IgM polyclonal antibody. what best describes the function of this reagent?

the reagent antibody binds the Fc region of cat IgM