DIFFERENTIATION OF B - These stages are of course initiated upon encounter with antigen and activation by T-cell lymphokines The activated B-cell

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DIFFERENTIATION OF B-LYMPHOCYTES B-cells begin their lives in the bone marrow as multipotential stem cells. These completely undifferentiated cells serve as the source for all of the cellular components of the blood and lymphoid system. The initial differentiation step that ultimately leads to the mature B-cell involves DNA rearrangements joining the D and J segments of the immunoglobulin heavy chain genes (click here for more information) . Next, DNA rearrangements joining the variable (V) region to the DJ segments of the immunoglobulin heavy chain, as well as similar rearrangements within the light chain genes gives rise to the pre- B-cell. Establishment of the B-cell specificity and consequent expression of surface immunoglobulin gives rise to the "virgin", fully functional B-cell. Each of these steps is entirely independent of antigen. The antigen-dependent stages of B-lymphocyte differentiation occur in the spleen, lymph nodes and other peripheral tissue.
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Unformatted text preview: These stages are, of course, initiated upon encounter with antigen and activation by T-cell lymphokines. The activated B-cell first develops into a B-lymphoblast, becoming much larger and shedding all surface immunoglobulin. The B-lymphoblast then develops into a plasma cell, which is, in essence, an antibody factory. This terminal differentiation stage is responsible for production of primarily IgM antibody during the "primary response". Some B-cells, however, do not differentiate into plasma cells. Instead, these cells undergo secondary DNA rearrangements that place the constant region of the IgG, IgA or IgE genes in conjunction with the VDJ genes. This "class switch" establishes the phenotype of these newly differentiated B-cells; these cells remain as long-lived "memory cells". Upon subsequent encounter with antigen, these cells respond very quickly to produce large amounts of IgG, IgA or IgE antibody, generating the "secondary response"....
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This note was uploaded on 11/05/2011 for the course BIOLOGY MCB2010 taught by Professor Jessicadigirolamo during the Fall '10 term at Broward College.

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DIFFERENTIATION OF B - These stages are of course initiated upon encounter with antigen and activation by T-cell lymphokines The activated B-cell

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