More Antibody Molecules than Genes in Our Genome

There are more than 1012 different antibody molecules in the human body. How can our body make more antibodies than there are genes in the genome? Explain the genetic rearrangement mechanism to produce the antibody diversity.

Immunoglobulins (antibodies) are a group of structurally related proteins produced by plasma cells, secreted into the serum or tissue fluids, and characterized by certain physicochemical and biological properties. Immunoglobulins of mammals can be divided into five major classes, usually called IgM, IgG, IgA, IgD and IgE, which differ physicochemically and immunologically (Zapata & Cooper, 1990). One of the most interesting questions about Ig is the source of immense variation observed in antibody-binding specificities. Different antibody molecules produced in response to a particular antigenic determinant may vary considerably in their tightness of binding to that determinant (Lydyard, Whelan, & Fanger, 2004). One of the source of diversity are causes by mechanisms of generation of antibody diversity such as V(D)J recombination system somatic recombinational diversity and also somatic mutation.

The generation of antibody diversity with different specificities is created when the region of the light chain V gene and J region or the heavy chain V gene and D and J regions, by their random combination and by imprecise joining. Those three unlinked group encode for immunoglobulin which is K chain, beta chain and heavy chain, each on a different chromosomes. Gene rearrangement happen when a single B cell randomly selects one V, one D and one J (for heavy chains), and one V and one J (for light chain) for rearrangement (translocation) and this were called V(D)J somatic recombination system as shown in figure 1. I...

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... amino acid changes which increase the tightness of binding of the antibody on the B cell to its antigen. These B cells will compete more efficiently for antigen than the original B cell, and will differentiate into plasma cells producing a higher-affinity antibody (affinity maturation), resulting increase of affinity to the antibody population to that antigen. After successive immunization, antibodies have binding constants of 108-9 M-1 but may be as high as 1012 M-1.

Works Cited

Lydyyard, P., Whelan, A., Fanger, M. (2004). Immunology (2nd ed.). UK: Taylor & Francis Group.

Sullivan & Bergman. (n.d.). Did immune system antibody diversity evolve?. Retrieved 24 December, 2013, from http://creation.com/immune-system-antibody-diversity.

Zapata, A. G., & Cooper, E. L. (1990). The immune system: Comparative Histophysiology. Chichester, New York: John Wiley & Sons Ltd.