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Antibodies Are Our Defense Mechanism

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The antibodies are the third line defense mechanism where they are presented on the B cells’ plasma membrane and function as antigen receptors (Karp, 2013). The B cells in our body are capable of producing antibodies, one of the proteins in our body. The number of antibodies in human body is more than 1012 and they are produced with or without the stimulation from antigens (Alberts et al., 2002). However, the number of genes encoding for antibodies is only approximately 20000 genes (Reece et al., 2011). The diversity of antibodies is due to DNA rearrangement of germ-line DNA to produce vast number of genes encoding for antibodies (Karp, 2013). The antibodies consist of light (L) chains (kappa and lambda) and heavy (H) chains which are linked by disulfide bonds as shown in Figure 1 (Karp, 2013). Both of the heavy and light chains consist of variable (V) and constant (C) region.

The immunoglobulin (Ig) genes are responsible in the production of membrane-bound and secreted antibodies (Reece et al., 2011). The production of light chain involves gene segments such as 40 variable (V) segments, 5 joining (J) segments, and a constant (C) segment. The variable region of the light chain is encoded by the variable and joining gene segments whereas the constant region is encoded by the constant gene segment. The assembly of each gene segment from variable and joining segments respectively with a constant segment to build a functional gene in germ cells is known as DNA rearrangement (Reece et al., 2011).

During the formation of kappa light chain as shown in Figure 2, the germ-line DNA is organized through somatic recombination (Karp, 2013). The linkage of a specific variable gene segment to a joining gene segment happens with the help of re...

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...Works Cited

Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., & Walter, P. Molecular biology of cell (4th ed.). New York, USA: Garland Science.

Immunoglobulin Gene Rearrangement. (n.d.). Retrieved 11 December, 2013 from http://www.oculist.net/downaton502/prof/ebook/duanes/pages/v8/ch025/005f.html

Karp, G. (2013). Cell and molecular biology: Concepts and experiments (7th ed.). USA: John Wiley & Sons.

Lefranc, M. P., & Huret, J. L. (2002). Atlas of genetics and cytogenetics in oncology and haematology. Retrieved from http://atlasgeneticsoncology.org/Educ/PolyIgEng.html

Microbiology and Immunology Mobile. (n.d.). Retrieved 11 December, 2013 from http://pathmicro.med.sc.edu/mobile/m.immuno-6.htm

Reece, J.B., Urry, L.A., Cain, M.L., Wasserman, S.A., Minorsky, P.V., & Jackson, R.B.

(2011). Campbell biology (9th ed.). USA: Pearson.