Antibodies

Question 1

What are Naive B cells?

Answer 1

Cells that have not met an antigen so have not yet been activated.

Question 2

How is lymph in lymphatic vessels moved about?

Answer 2

By muscular contraction

Question 3

What are Geminal Centres

Answer 3

They are located in lymph nodes and they are multiplying centres of B cells. During infection, they become swollen and tender as they are producing many B cells

Question 4

How do antigens enter the spleen?

Answer 4

Through blood rather than lymph. The spleen also has geminal cells

Question 5

Describe the course of an antibody production upon meeting an antigen

Answer 5

The primary adaptive response - initial meeting of an antigen, produced some antibodies over longer period of time Adaptive response - Upon meeting antigen for second time the body produces a stronger and faster response. because of antigen specificity and memory. Responses to multiple antigens can occur simultaneously.

Question 6

Describe some of the basic features of antibodies (Ab)

Answer 6

• Expressed as membrane bound (receptor on B cell) or can be secreted - B cells only produce one type of antibody - Two functions; bind to pathogen and recruit other cells and molecules. - Composed of four polypeptide chains; two heavy, two light - Two light chains exist as either lamba or kappa.

Question 7

Describe the antibody structure

Answer 7

Variable region at the top of the “Y” where the antibody recognises pathogens, consisting of two heavy chains and two light. And the constant region below variable regions and base. This part recruits other components.

Question 8

What is the importance of being able to separate antibodies?

Answer 8

Useful in laboratories as the fragments can be used to label cells without inducing the effects of the Fc region (the constant region)

Question 9

Where is all the variability of antibodies located?

Answer 9

In the V domains, of which there are three; HV1, HV2 and HV3

Question 10

How can you generate antibody diversity?

Answer 10

The Somatic Diversification Theory proposed that genetic variation is from a limited number of V region genes that under gene alteration. Extra variability is created by Junctional Diversity.

Question 11

Describe what occurs in Junctional Diversity

Answer 11

Section of DNA is cleaved and the gap left is filled by a nucleotide and then pairing of the two ends is attempted. However they often don’t match up so it is not a very efficient process.

Question 12

Describe all the ways of creating genetic diversity in antibodies

Answer 12

1. rearranging multiple gene segments 2. Junctional Diversity 3. Different combos of H and L chains 4. Somatic hypermutation

Question 13

What is somatic hypermutation

Answer 13

This occurs during an immune response, it is where more mutations accumulate in the V regions of H and L chain genes. Some mutations will improve antigen binding, these cells are selected to expand and secrete antibodies (affinity maturation)

Question 14

Name the five classes on antibodies and how they are defined

Answer 14

Defined by heavy chain and classes are; IgG, IgM, IgD IgA and IgE (Gav Made Dad An Egg)

Question 15

What is the antibody that is most present?

Answer 15

IgG. Antibodies exist at different concentrations and each class has different abilities

Question 16

What antibody exists on the surface of B cells

Answer 16

IgM antibodies, as membrane bound IgM.

Question 17

Describe the different structures of IgM and IgA antibodies

Answer 17

IgA exists as a dimeric IgA and IgM can exist as both monomeric and pentameric IgM

Question 18

What antibody can be secreted and explain how this works

Answer 18

IgA can bind to a receptor on an epithelial cell and then be transports through the cell and secreted at the other side.

Question 19

Describe the distribution of different antibodies

Answer 19

• IgG and IgM predominate in plasma - IgG and IgA are in extracellular fluid - IgA predominated in secretions including breat milk - IgG goes to foetus - IgE is found near epithelial surfaces Brain free of antibodies

Question 20

Describe the function of antibodies with blocking a virus/toxins

Answer 20

Antibodies bind to the surface of a virus preventing it from interacting with receptors on cells. Antibodies can also block the binding of a toxin to the cell-surface receptor

Question 21

What are some of the features of antibody-antigen complexes?

Answer 21

They are an important mechanism for clearing soluble antigens and are taken up by phagocytes. However high levels of antibody-antigen complexes are prevelent in some autoimmune diseases

Question 22

Name some monoclonal antibodies and what they are used for

Answer 22

Infliximab - anti-Tumour Necrosis Factor (inflammatory mediator) used in rheumatoid arthritis, inflammatory bowel disease, psoriasis Herceptin - anti HER2 factor. Can block growth and lead to destruction of breast tumour cell that express high levels of HER2 Gleevac - Anti-tyrosine kinase. Effective against chronic myeloid leukemia.