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details of B-cells

A B cell has internalized a toxin that contains the epitope recognized by its surface Ig. Describe how this cell would be activated, the cellular and molecular interaction(s), and the various steps and factors leading to an appropriate immune response to clear the toxin

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Immunology has always been one of my favourite subjects, how nice for you to be taking it as a graduate course. The complexity of the B-cell response to antigens is just one of the many amazing mammalian adaptations to potentially fatal invasions of the body by foreign agents. I will outline a B-cell response step by step, starting with engulfment of the toxin by receptor-mediated endocytosis. The engulfed toxin is itself soluble and is considered an "exogenous" antigen because it was produced "outside" the body. Endogenous antigens are generated inside the body, and are comprised of epitopes from things like viruses or bacteria. This distinction is important because the immune response differs in each case.

First, let's review the details of B-cells:

Each individual has thousands of different B-cells. Each B-cell in turn recognizes a distinct, specific protein antigen epitope, a feat that is achieved through the diversity of B-cell receptors (surface Immunoglobulin or Ig). The B-cell receptor is an integral membrane protein (ie. it has a heavy chain that has many hydrophobic amino acid residues and is therefore able to embed in the plasma membrane). Thousands of copies of the B-cell receptor are present on the surface of the B-cell. They are generated before the cell ever encounters an antigen and are encoded by genes assembled by the recombination of segments of DNA in the nucleus of the ...

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This job summarizes details of B-cells.