IgGene Expression Is Inhibited in T Cells

As noted earlier, germ-line DNA encoding the T-cell receptor (TCR) undergoes V-(D)-J rearrangement to generate functional TCR genes. Rearrangement of both immunoglobulin and TCR germ-line DNA occurs by similar recombination processes mediated by RAG-1 and RAG-2 and involving recombination signal sequences with one-turn or two-turn spacers (see Figure 5-7). Despite the similarity of the processes, complete Ig-gene rearrangement of H and L chains occurs only in B cells and complete TCR-gene rearrangement is limited to T cells.

Hitoshi Sakano and coworkers have obtained results suggesting that a sequence within the K-chain 3' enhancer (3'KE) serves to regulate the joining of VK to JK in B and T cells. When a sequence known as the PU.1 binding site within the 3' K-chain enhancer was mutated, these researchers found that VK-JK joining occurred in T cells as well as B cells. They propose that binding of a protein expressed by T cells, but not B cells, to the unmutated K-chain enhancer normally prevents VK-JK joining in T cells. The identity of this DNA-binding protein in T cells remains to be determined. Similar processes may prevent rearrangement of heavy-chain and X-chain DNA in T cells.

Was this article helpful?

0 0
How To Bolster Your Immune System

How To Bolster Your Immune System

All Natural Immune Boosters Proven To Fight Infection, Disease And More. Discover A Natural, Safe Effective Way To Boost Your Immune System Using Ingredients From Your Kitchen Cupboard. The only common sense, no holds barred guide to hit the market today no gimmicks, no pills, just old fashioned common sense remedies to cure colds, influenza, viral infections and more.

Get My Free Audio Book

Post a comment