Chapter 5 - B cells and Antibodies of Adaptive Immunity At the end of this Chapter, students should be able to: . Explain the structure of the B cell receptor complex and immunoglobulins. . Relate the structure of the B cell receptor complex to the T cell receptor complex - noting similarities and differences. 1
Chapter 5 - B cells and Antibodies of Adaptive Immunity In many ways, B cell development is a lot simpler than T cell development. Major developmental stages of developing cells can be tracked by changes in expression of the B cell receptor, also called Ig, as well as the specific type of Ig. In the bone marrow: HSC-> CLP ->B cell precursor -> Immature B cell -> Mature B cell (naïve) lg IgM+ IgM + IgD + Not committed to B cell development Committed to B cell development About 40% of the cells that commit to becoming a B cell actually mature into B cells. 2 superscripts: (-) means that the protein in not made, (+) means that the protein is made
Chapter 5 - B cells and Antibodies of Adaptive Immunity Each BCR is generated from the random selection of gene segments. / Each B cell has its own unique version of the BCR, and approximately has ~10,000 identical copies. Variable region The uniqueness is concentrated in the "variable" region of the heavy (H) and light (L) chains. There is some variability here in terms of amino acid sequence, but also some conserved regions. You can potentially make over 1013 different BCRs (B cell "repertoire"). Like the TCR, the BCR is also associated with a signalling complex, known as Iga/lgß. Constant region L chain + H chain Igß Iga 3