2-27 B-Cell Immunity Flashcards Preview

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Flashcards in 2-27 B-Cell Immunity Deck (10):

What are the early checkpoints in B-cell development?

  1. Pre-B-cell receptor: Selects for functional heavy chains (rearrange D-J regions, then V-DJ regions)
  2. B-cell receptor: Selects for functional light chains (rearrange κ genes on 1st, then 2nd chromosome; next, λ genes on 1st, then 2nd chromosome)

Multiple gene rearrangements can rescue cells from apoptosis.

Cells that have completed rearrangements express a functional IgM receptor on their surface.


How do B1 and B2 cells differ?

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What do central and peripheral tolerance accomplish, and where do they do it?

Central and peripheral tolerance eliminate self-reactive B cells.

Central tolerance occurs in the bone marrow.

Peripheral tolerance occurs AFTER B-cell development.


What is receptor editing in B cells?

Randomly generated B-cell receptors may bind to self-ligands, which creates a potential for self-reactivity. Re-expressing RAG genes and rearranging another light chain can modify the receptor and avoid the danger.

The alternative light chain generates a new specificity; if this does not bind to self, B-cell development continues. Receptor editing makes B-cell development more efficient.


What are the stages of B-cell development that take place in the bone marrow?

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What are the stages of B-cell development that take place when the B cells leave the bone marrow?

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What is the structure of the B-cell co-receptor?

Complex of 3 proteins:

  1. Complement receptor 2 (CR2/CD21) recognizes iC3b and C3D
  2. CD19 protein, signaling chain
  3. CD81, function unknown


How and why do B cells interact with T cells?

B-cell responses to most antigens require the assistance of helper T cells, which drive B-cell proliferation and differentiation.

  • B cells process antigens to peptides and present them to CD4 T cells via class II MHC
  • B and T cells meet at the border of the B and T cell zones in 2° lymph tissues
  • B cell must find a cognate T cell that recognizes the peptide presented
  • CD4 T cells activated → produce factors that promote B-cell proliferation and differentiation
  • Further B cell-T cell intrxns occur in germinal centers (GCs) → promote receptor class switching and somatic mutation
  • B cells differentiate to memory cells or antibody-secreting plasma cells


What are plasma cells?

Essentially, long-lived antibody factories. They are a differentiated form of B cells that secrete Ig at a high rate.


What are memory cells?

Rare, resting, long-lived cells, with unique properties. Typically class-switched cells that produce high-affinity antibodies following secondary infection.