What is at cell receptor excision circle?

T-cell receptor excision circles (TRECs) are small circles of DNA created in T-cells during their passage through the thymus as they rearrange their TCR genes. Their presence indicates maturation of T cells; TRECs are reduced in SCID (Severe combined immunodeficiency disease).

What is TREC Analysis?

Thymic function can be determined by T-cell receptor excision circle (TREC) analysis. TRECs are extrachromosomal DNA byproducts of T-cell receptor (TCR) rearrangement, which are nonreplicative. TRECs are expressed only in T cells of thymic origin and each cell is thought to contain a single copy of TREC.

What enzyme makes TRECs?

Congenital Disorders of Lymphocyte Function SCID can be diagnosed at birth by measuring levels of TCR excision circles (TRECs). TRECs are a byproduct of V(D)J recombination and are present as circularized DNA fragments in newly generated, naive T lymphocytes that express the αβ form of the TCR.

What is the significance of TREC?

The formation of new T cells occurs in the thymus and as a byproduct, T cell receptor excision circles (TRECs) are released. Detection of TRECs by PCR is a reliable method for estimating the amount of newly formed T cells in the circulation and, indirectly, for estimating thymic function.

How are TRECs formed?

TREC are circular DNA molecules formed within T-cells developing in the thymus. TREC DNA circles are measured by a technique called polymerase chain reaction (PCR). Normal infant blood samples have one TREC per 10 T-cells, reflecting the high rate of new T-cell generation early in life.

How does Vdj recombination work?

VDJ recombination is the process by which T cells and B cells randomly assemble different gene segments – known as variable (V), diversity (D) and joining (J) genes – in order to generate unique receptors (known as antigen receptors) that can collectively recognize many different types of molecule.

Can you live with SCID?

What are the survival rates for SCID? Without treatment, infants with SCID usually die from infections within the first two years of life. With an early bone marrow transplant, frequent follow-up and prompt treatment for infections, survival rates are very good.

During what process are TRECs created?

Therefore, TRECs are the excised DNA circles formed during the process of TRA chain VJ recombination (Figure 1A). In B-cell maturation, K-deleting recombination excision circles (KRECs) are the products of recombination events determining the allelic and isotypic exclusion of the Ig kappa (IGK) locus [7–9].

What is trec and KREC?

T-cell recombination excision circles (TREC) and kappa-deleting element recombination circle (KREC) in a dried blood spot and in peripheral blood using real-time polymerase chain reaction (PCR) are used as a tool for severe combined immune deficiency but not in PID.

Where are the T cell receptor excision circles located?

T-cell receptor excision circles (TRECs) are small circles of DNA created in T-cells during their passage through the thymus as they rearrange their TCR genes.

Why are T cell excision circles not a direct measure of thymic output?

While indicative of thymic function and T-cell recovery, T-cell receptor excision circle (TREC) results cannot be taken as a direct measure of thymic output because TREC are diluted by peripheral T cell division and intracellular degradation.

What do the circles on a T cell mean?

Their presence indicates maturation of T cells; TRECs are reduced in SCID (Severe combined immunodeficiency disease). Signal joint T-cell receptor excision circles (sjTRECs) might be used as a way to test the age of the individual from a blood sample.

Can a TREC assay be performed on an adult?

The TREC assay should not be ordered on adults over age 60 due to physiological decline in thymic function in the sixth and seventh decades of life. Assay results are dependent on the patient’s T-cell counts and in patients with profound lymphopenia it may be impossible to perform the assay if there are insufficient numbers of cells.