IMMUNESYSTEM5_Lectureppt_Ch06 (copy)

what are the six functional phases of B-cell development?

Repertoire assembly, Negative selection, Positive selection, Searching for infection, finding infection and attacking infection.

Where do the phases of B cell development occur?

The first three phases occur in the bone marrow, and the last three occur in secondary lymphoid tissues.

Which cells stimulate B-cell development in the bone marrow?

Bone marrow stromal cells

What is the role of the pre-B-cell receptor?

It monitors the quality of the immunoglobulin heavy chains and halts further heavy-chain rearrangement.

What happens if a pro-B cell fails to successfully rearrange its immunoglobulin heavy-chain genes?

It undergoes apoptosis (cell death).

what are the two checkpoints during B-cell development?

The first is for heavy chain rearrangement and the second is for light-chain assembly

What process allows self-reactive B cells to avoid deletion?

Receptor editing, which changes the antigen specificity of B-cell receptors.

What is the outcome for immature B cells that recognize multivalent self-antigens?

They are retained in the bone marrow and do not continue maturation.

What types of cells do activated B cells differentiate into?

Plasma cells and memory B cells.

Which type of chromosomal translocation is commonly associated with Burkitt’s lymphoma?

Translocation between chromosomes 8 and 14, involving the MYC gene and immunoglobulin heavy-chain gene.

What is the function of the chemokine CXCL13 in B-cell maturation?

It attracts B cells to primary lymphoid follicles, where they undergo final maturation.

What is the function of the protein kinase FLT3 during B-cell development?

FLT3 is a receptor on stem cells that, when bound to FLT3 ligand, initiates differentiation into common lymphoid progenitors.

What is the first immunoglobulin expressed on the surface of immature B cells?

IgM

How do bone marrow stromal cells support early B-cell development?

They provide growth factors like IL-7 and adhesion molecules that interact with developing B cells.

What are the consequences of nonproductive rearrangements in immunoglobulin genes?

If both heavy-chain alleles rearrange unsuccessfully, the B cell dies. If the light-chain rearrangement is unsuccessful, further rearrangements may occur.

What role does the adhesion molecule VCAM-1 play in B-cell development?

It binds to the integrin VLA-4 on B cells, facilitating interactions with stromal cells that promote B-cell proliferation.

What is the difference between B-1 and B-2 cells?

B-1 cells develop during fetal life, have low diversity, and self-renew, while B-2 cells are produced throughout life and have higher diversity.

What happens to immature B cells that recognize monovalent self-antigens?

They enter a state of anergy (non-responsiveness) and do not initiate immune responses.

How do B cells enter secondary lymphoid tissues?

They enter via high endothelial venules (HEVs), attracted by chemokines like CCL19 and CCL21.

What is receptor editing in B cells?

Receptor editing is the process of continuing light chain rearrangement in self reactive B cells to alter antigen specificity and prevent autoimmunity

What is the significance of the BAFF protein in B-cell maturation?

BAFF (B-cell Activating Factor) is critical for the survival and maturation of B cells in lymphoid follicles.

At which stage does rearrangement of the light-chain genes occur?

In pre- B cells

What signals the cessation of heavy-chain gene rearrangement in developing B cells?

Successful signaling by the pre-B-cell receptor.

What are the two main functions of the surrogate light chain in the pre-B-cell receptor?

It helps test the quality of the heavy chain and triggers signaling for further development.

What type of genetic alteration is frequently associated with B-cell tumors?

Chromosomal translocations involving immunoglobulin genes

What is the role of Pax-5 in B-cell development?

Pax-5 is a transcription factor that activates genes necessary for B-cell differentiation and immunoglobulin gene rearrangement.

What are the primary differences between immature and mature B cells?

Immature B cells express IgM and are still undergoing selection processes, while mature B cells express both IgM and IgD and have completed their development.

What is the function of follicular dendritic cells (FDCs) in B-cell maturation?

they present antigens and provide survival signals necessary for the final maturation of B cells in lymphoid follicles.

What is the significance of IgM and IgD co-expression on mature B cells?

It indicates that the B cell is fully mature and capable of responding to antigens