Summary
Background: Patients with Down syndrome (DS) are more likely to exhibit
immunological abnormalities that predispose them to infection. Among
other anomalies, individuals with DS have altered serum concentrations
of some subclasses of Immunoglobulin G (IgG), particularly the IgG4
subclasses The aim of the present study was to investigate the molecular
mechanism of low serum IgG4 at the level of the heavy chain gene
(IGHG4 ).
Method: Quantitative real-time
polymerase chain reaction (qPCR) was carried out to measure the number
of IGHG4 copies and to compare those outcomes with a reference
gene (36B4 ). An IGHG4/36B4 ratio was considered normal
(two copies of IGHG4 ) when between 0.8 and 1.2. We studied 44 DS
patients from 8 to 57 years of age, comprising 23 DS persons carrying
severe low serum IgG4 (< 0.02 g /L), with five having an IgG4
level that was not detectable, and 21 DS patients with normal serum IgG4
(level > 0.1 g /L). The patient group was compared with 38
healthy donors (controls) without DS.
Result: IGHG4 heterozygous deletion was found in 16 (69.6%) DS
patients with low serum IgG4 versus in two (9.5%) DS with normal serum
IgG4 (P =0.0001 ). In the control group, deletion was found in
5.26% (2/38) of the sample.
Conclusion: IGHG4 haploinsufficiency is highly correlated with
low serum IgG4 in our population with DS, but other relevant factors
must to be assessed in future work.
Key words: Down syndrome, Low serum Immunoglobulin G4,
Immunoglobulin heavy chain G4 gene, qPCR.