B cell Ontogenesis

Question 1

Outline the goals of B cell development.

Answer 1

(1) To generate diverse antigen receptors
(2) To alter or eliminate self-reactive B-cells/B-cell receptors
(3) To promote foreign reactive B cells to become mature B cells in the secondary lymphoid tissues

Question 2

Discuss the process of B cell development [from HSC to Immature B cell].

Answer 2

🧬 B cells originate from hematopoietic stem cells in the bone marrow.
🧬 Hematopoietic stem cells differentiate into Common Lymphoid Progenitors, which give rise to both B and T cells.
🧬 CLPs differentiate into early pro-B cells. This stage is marked by the initiation of heavy chain gene rearrangement.
🧬 Early pro-B cells mature into late pro-B cells, completing the heavy chain gene rearrangement.
🧬 Following the successful rearrangement of the heavy chain genes, late pro-B cells transition into pre-B cells, which express the pre-B cell receptor (pre-BCR) on their surface.
🧬 Pre-B cells then undergo light chain gene rearrangement.
🧬 Once light chain rearrangement is successful, the pre-B cell expresses a complete BCR, which is surface IgM.
🧬 Immature B cells undergo a selection process to eliminate those that strongly react with self-antigens, preventing autoimmunity.
[Diagram 1] [Diagram 2] [Diagram 3]

Question 3

Discuss the process of B cell development [from immature B cell to mature B cell].

Answer 3

🧬 After passing the selection process, immature B cells leave the bone marrow and migrate to secondary lymphoid organs such as the spleen, lymph nodes and MALT.
🧬 In the secondary lymphoid organs, immature B cells further mature and start expressing both IgM and IgD on their surface.
🧬 These mature B cells are now fully capable of responding to antigens. They can participate in immune responses by producing antibodies, presenting antigens, and interacting with other immune cells.
[Diagram 1] [Diagram 2] [Diagram 3]