Antibody Diversity Mechanism Essays

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A transposition- like mechanism can be used for other types of DNA rearrangement reactions. Such mechanism is responsible for assembly of gene fragments during development of the vertebrate immune system. Vertebrates have two specialized cells namely T- cells and B-cells that dedicated to recognize the invading organism. B cells produce antibodies that circulate in the bloodstream. T-cell produce cell surface- bound receptor protein called T-cell receptor. These classes of protein able to recognized great diverse invader molecule then starts a cascade event to destruct the invader.
Antibody diversity is generated by the rearrangement of variable region gene segments during the differentiation of the antibody- producing cells by a series
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Human has 50 genes VH, 40 genes Vϰ and 40 genes Vλ (Albert et al., 2002).
Combinatorial joining of gene segments magnifies antibody diversity by random rearrangement of VJ and VDJ in somatic cells. 40 Vϰ and 5 Jϰ genes able to form 200ϰ chain combinations. 40 Vλ and 4 Jλ genes able to form 160λ chain combinations. 50 VH , 20 D and 6 JH genes approximately form 6,000 H chain combinations.
Junctional diversification during gene segment joining is the imprecise joining and random insertion. The recombination between V-J and V-D-J is not always perfect and if errors occur during recombination event, additional diversity occurs. The diversity generated by this mechanism is occurring in the third hypervariable region thus directly affecting combining site of the antibody. After the hairpin loop is opened, thr free DNA ends can be trimmed cause the loss of nucleotides from the free end. Pier, Lyczak and Wetzler (2004) believe that exonuclease activity is involved. Exonuclease activity is not only removed P-nucleotides that already added to gene but also nucleotides that were originally part of the immunoglobulin gene. Junctional diversity also has the potential to alter the reading frame of exon.
Any B cell has potential of combinatorial joining of possible light and heavy chains before transcribed. Thus dissimilar combinations of light and heavy chains within individual B cells add further diversity.

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