Lymphocyte Development

Question 1

Also what receptor detects them ?

What types of immunoglobulins are there and what do they do?

Answer 1

• IgM: Primary response to infection
• IgE: Secondary stronger response (alos responsible for allergic reactions)
• IgA: Mucosal Immunity
• IgG: Most common, enhnaces phagocytosis
• IgD: Unknown function
  Fc Receptors: Ig receptor i.e FcE binds IgE

Question 2

Describe the process of lymphopoiesis

Answer 2

Large lymphoblasts converted to small lymphoblasts - if lymphoblast remains in the bone marrow it becomes a B-Cell (Plasma cells) if lymphoblast transported to the thymus it becomes a T- cell (Cytoxic, Helper, Regulatory).
Bone Marrow and Thymus = Primary lymphoid organs

Question 3

What does maturation of the lymphocytes involve?

Answer 3

Gene rearrangement, lineage commitment, education and functional maturation

Question 4

What proteins do B and T cells recognise?

Answer 4

B-cells recognise native (own) proteins whereas, T-cells recognise degraded proteins that are bound by MHC molecules

Question 5

What are the gene chains that make up an antibodies light chain?

Answer 5

V = Variable
J = Joining
C = Constant

Question 6

In the alpha chain of T-cell receptor what are the gene segments?

Answer 6

V = Variable
J = Joining
C = Constant

Question 7

How do we generate diversity of lymphocytes and TCRs?

Answer 7

Multiple gene isoforms of the V and J segments:
For example in humans we have 2,700,000 different possible outcomes for immunoglobulin molecules
The recptor for T-cells also has multiple gene segments that can be selected with the ability of generating 5,700,000 different TCRs
Selection of gene segments in both cases is completley random

Question 8

How can Antigen drive diversity of B-cells?

Answer 8

Somatic Mutations: Occurs in Germinal Centres -
A mechanism by which mutations are introduced into the variable region of activated B-cells (antigen driven) increasing antibody affinity (mutate closest matching antibody to perfectly match the antigen)
However one single viral mutation changes the affinity of the immune response

Question 9

Can antigen drive TCR diversity?

Answer 9

Receptor unable to change once created, diversity is more focused on the complementary determining region

Question 10

What does a stem cell need to do to become a lymphocyte?

Answer 10

Needs to express an antigen receptor by undergoing gene rearrangement (B-Cell), for a T-cell it needs to express a receptor and undergo gene rearrangement

Question 11

How is the microenvironment important for lymphocyte development?

Answer 11

The microenvironment (stromal cells) facilitate the development of B cells by providing suitable factors and cell-cell interactions

Question 12

Describe the process of positive and negative selection of lymphocytes

Answer 12

To generate functional T-cells that are capable of recognising foreign antigen in the context of self MHC - destroy T-cells that produce a response when self MHC presents self pepties and keep those that recognise self-MHC foreign antigen complexes and produce an immune response

CD8 and CD4 t-cells recognise different classes of MHC

Question 13

What is the primary function of the thymus?

Answer 13

Production of T-cells:
- Upon entry into the thymus, stem cells recieve the necessary signals to become functional mature t-cells
- Thymic microenvironment responsible for the signals (thymic endothelial cells) involving cell-cell and production of soluble factors