In an individual B cell, only one of the chromosomes undergoes complete V-D-J recombination leading to expression of heavy and light chains. A mechanism exists that prevents the other chromosome from being rearranged and therefore expressed in the same cell. This is called allelic exclusion. It prevents a B cell from expressing two entirely different immu-noglobulins or BCRs. A similar mechanism operates during synthesis of TCRs in T cells [see T Cell Receptors, below].
The most intriguing aspect of the genetic control of im-munoglobulin synthesis is the diversity of the product: plasma cells can make antibodies that react with an indefinite number of different antigenic sites. How can DNA code for such a large number of antigens, many of which have only recently (on the evolutionary time scale) come into existence?
Book Review: Lehninger Principles of Biochemistry - …
Intrathecal synthesis of immunoglobulin gamma (IgG) synthesis is frequently observed in patients with multiple sclerosis (MS). Whereas the extent of intrathecal IgG synthesis varies largely between patients, it remains rather constant in the individual patient over time. The aim of this study was to identify common genetic variants associated with the IgG index as a marker of intrathecal IgG synthesis in MS.