T-cell Receptor Excision circles (TRECs) are circular DNA fragments generated during T-cell receptor rearrangement. In healthy neonates, TRECs are made in large numbers, while in infants with SCID they are barely detectable. Following PCR amplification TREC copy number in blood can be used to distinguish T-cell lymphopenic SCID infants from healthy babies. However, low TRECs copy numbers can also be the results of other immunodeficiency, such as DiGeorge Syndrome, and sometimes as a result of the use of immunosuppression drugs. Confirmatory tests are needed for the diagnosis of SCID and for the determination of the form of SCID.
Figure 3. TRECs are circular DNA
fragments. They are generated when a
section of chromosome 14 (14q11-2),
which contains genes responsible for
coding T-cell receptors, rearranges. The
TRECs are amplified by PCR.