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There are several families of antibodies found in mammals. They may have two or more antibody domains which contain heavy and light chains. The variable regions of the light and heavy chains genes in the chromosome are spliced in antibody producing cells so that each cell produces a different antibody, with a unique sequence of amino acids in the variable regions.

Here's a cartoon:

enter image description here

The variable regions are disproportionately large here, but it gives some idea...

What I'm having trouble finding is how the DNA regions of these genes look in cells which don't produce antibodies. Are they the same as that in the germline? Do they undergo recombination but are not expressed?

Any help would be appreciated.

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I can't find a definitive reference, but I'm pretty sure that Ig gene rearrangement is a phenomenon that is restricted to lymphoid cells. See WP for an assertion that expression of the specific recombinases is limited to lymphocytes. – Alan Boyd Apr 6 '13 at 8:13
If "cells that don't produce antibodies" means generally all other kinds of cells (e. g. skin cells or so), then the answer is: yes, the DNA regions are the same as the germline. The VDJ recombination bharat_iyengar mentioned is a controlled procedure that has to be initiated and doesn't occur randomly. If you refer to lymphoid cells that do not yet express antibodies, the answer is: that depends. It depends on the state the cell is in, because it is done in distinct steps (pre-B cells are different from pro-B cells). – suvidu Apr 8 '13 at 11:14
up vote 2 down vote accepted

Perhaps you want to ask how VDJ recombination is regulated in non lymphoid cells..

Well even in immature lymphoid cells VDJ recombination is regulated. And also Ig genes are suppressed in T-cell and TCR genes are suppressed in B-cells.. Also, the recombination of Ig is suppressed in T-cell and vice-versa.

RAG-1,2(Recombination activating gene) downregulation partly does the job, but not fully.

Earlier reports say that transcription in the locus is essential and epigenetic regulation of transcription in turn regulates recombination. But what it exactly means is that accessibility to the RSS (Recombination signal sequences) is limited in a repressed chromatin and recent reports say that nucleosomes are appropriately positioned over the RSS to control recombination.

Have a look at these:

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Thanks for pointing out how many varieties of cells have VDJ recombination. It sounds like getting a germline Ig sequence would be the typical result. – shigeta Apr 8 '13 at 12:06
There are the IgG sequences in the germline along with several pseudogenes. They are kept repressed.. Have a look at this. Perhaps this is what you are looking for: – WYSIWYG Apr 8 '13 at 12:37
Also, check this out. – WYSIWYG Apr 8 '13 at 12:43
This is why I normally try to avoid immunology - the cell differentiation and function leads to as many new questions as answers... thanks! – shigeta Apr 8 '13 at 17:32
immunology always full of anomalies :P – WYSIWYG Apr 8 '13 at 18:04

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