PMI 126 - Lecture 13

PMI 126 Lecture 13 - PMI 126 Lecture(MT3 start B cell development/maturation defined by both cell-surface expression of proteins characteristic of

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PMI 126 Lecture (MT3- start) B cell development/maturation - defined by both cell-surface expression of proteins characteristic of various stages of B cell development and the status of Ig gene rearrangement Bone marrow – site of B cell maturation (largely mature) Transitional B cell – B cells that come out the bone marrow. Once the functional BCR is created on the B cell in the bone marrow, negative selection of B cells occur (in the bone marrow). => negative selection: get rid of the autoreative B cells. Lymph node: T-cell zone: paracortex B-cell zone: cortex (has follicle – accumulation of B cells, where B cells have to arrive to last longer) Transitional B cells have functional Ig receptor on the surface go into peripheral blood scatter out and into organized lymphoid tissue as naïve, transitional B cell In the lymphoid tissues, naïve, transitional B cells investigate the possible antigens in the lymphoid tissues progenitor B cell undergoes gene rearrangement of immunoglobulin genes in the bone marrow, these B cells which undergo gene rearrangement also undergo selection ( INDEPDENT of antigen) o generation of antigen-specific receptor is created by chance (not directed by antigen!) In Peripheral lymphoid organ (organized lymphoid tissue) naïve B cells come in o does encounter antigen: going to apoptosis (90% of naïve B cells) o encounter antigen: naïve B cells proliferate 2 things occur to the progenies of the proliferated B cells in the presence of T helper cell : 1. Class switching (from IgM to other subclasses) 2. affinity maturation (As B cells proliferate, the progenies are going to compete for the antigen under the influence of T helper cell) a. these is a high rate of somatic mutation that’s directed toward hypervariable region of heavy and light chain. i. Result increased affinity = the selected B cells
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Progenitor -> early pro-B cell -> late pro-B cell -> Pre-B cell -> Immature B cell Developing B cells have to maintain contact with bone marrow stromal cells to avoid apoptosis. Stromal cells Secrete cytokine that drives the maturation of B cells (such as gene rearrangement) Once a functional IgM is formed on the surface of immature B cell, it’s released from stromal cell! (can leave the bone marrow) Phase 2: negative selection of B cells in the bone marrow. (multiple ways to make sure there are very few number of autoreative B cells get out the bone marrow.) Inactivation – anergy (non-responvie), or under go apoptosis. This has a chance to fix the B cell by fixing the light chain gene. Phase 3: don’t really know what’s going on it there. transitional B cells can get into the lymphoid tissue but only some of them gain access to get
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This note was uploaded on 05/09/2010 for the course PMI PMI 126 taught by Professor J.l.stott during the Winter '10 term at UC Davis.

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PMI 126 Lecture 13 - PMI 126 Lecture(MT3 start B cell development/maturation defined by both cell-surface expression of proteins characteristic of

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