Flashcards in Immunology Lecture 10. Deck (31):
What is the life cycle of a B cell?
1. generation of diverse and clonal expressed B-cell receptors in bone marrow 2. alteration, elimation, or inactivation of B cell receptors that bind to self (negative selection) 3. promotion of a fraction of immature B cells to become mature B cells in secondary lymphoid tissues (positive selection - not important like with T cells) 4. recirculation of mature B cells between lymph, blood, and secondary lymphoid tissues 5. activation and clonal expansion 6. differentiation to antibody-secreting plasma cells
Where do B cells develop?
What stage do B cells exit the bone marrow?
mature naive B cells (have not yet seen antigen)
What do B and T cells develop from?
pluripotent progenitor cells
marker for pluripotent hematopoietic stem cell
What is the immunoglobulin status of an immature B cell?
a heavy and light chain. IgM on surface
What does a pre-BCR do?
signals that a functional receptor has been made (from heavy chain - no light chain made yet)
What is the importance of allelic exclusion with B cells?
gives homogeneous B-cell receptors with high-avidity binding
What are most B cell light chains?
kappa (as opposed to lambda) because kappa chain always made first
What are the two checkpoints in B cell development?
pre-B cell receptor - (selects for functional heavy chains) AND B-cell receptor (selects for functional light chains)
adds diversity in junctional regions (N nucleotide addition)
caused by a chromosomal aberration during B cell development - oncogenic effect
What is the difference between a B1 cell and a B2 cell?
B1 produced by a fetus, more primitive, less developmental steps (more IgM) - self renewing, no need for T cell help
What happens when a B cell reacts with self antigen?
immature B cell is retained in bone marrow where it goes through receptor editing (or dies)
What happens when B cells binds to self antigen in periphery?
signaled to make IgD and become unresponsive to antigen, does not survive for long
Where do B cells make final maturation?
What is the main purpose of lymph nodes?
bring immune cells together
What is a germinal center?
where maturation of B cells into high affinity happens (also plasma cells and memory cells) - intense competition for limiting antigen (somatic hypermutation)
What stage in development does Hodgkin’s lymphoma arrise from?
germinal center B cell
What stage in development does multiple myeloma arrise from?
plasma cell (hybridoma - monoclonal antibody)
What is the order of development with B cells?
stem cell —> pro-B cell —> pre-B cell —> immature B cell —> mature naive B cell—> antigen activated lymphoblast (isotype switching) —> antibody-secreting plasma cell —> memory cell
What happens to a B cell in the periphery?
naive lymphocytes arrive at lymph nodes in arterial blood, lymphocytes and lymph return to blood via lymphatics, venous blood returns to heart (pathogens from site of infection reach lymph nodes via lymphatics) - die if they don’t encounter antigen
What defines B cells?
How do B cells signal?
cross-linking of B cell receptors by antigen, phosphorylation, signaling cascade begins that creates activating signals
Under what circumstance is T cell help not needed in B cell activation?
on B cell - CD40L on T cell activates, also causes release of IL-4,5,6 which cause B cell proliferation, resting memory cells, and plasma cells
induces IgG and IgE
augments production of IgA
What happens in medullary cords of lymph nodes?
What is the main property of plasma cells?
just Ig secretion - don’t switch, don’t grow - factories