Establishment of gene copy number-specific normal ranges for serum C4 and its utility for interpretation in patients with chronically low serum C4 concentrations.

Objective: To establish gene copy number (GCN)-specific normal ranges for serum C4 genes and to determine their utility with respect to the interpretation of chronically low serum C4 concentrations in patients with clinically quiescent systemic lupus erythematosus (SLE).

Methods: C4 serum concentrations were estimated by automated turbidimetry, and C4 GCNs were determined using the TaqMan real-time polymerase chain reaction (PCR) analysis in 184 unselected individuals and in 10 patients with type 1 diabetes mellitus (DM) who were selected for the presence of only 2 copies of the C4 gene. C4 GCNs were also determined in 11 patients with clinically quiescent SLE who had chronically low serum C4 concentrations.

Transcription factor GATA-3 is involved in repression of promoter activity of the human interleukin-4 gene.

GATA-3 was shown to bind to two sites of the IL-4 gene promoter in human T-cell lines PER-117 and Jurkat. A motif located in the region of position -860 and responsible for GATA-3 binding was detected for the first time. Mutation or deletion of this site increased the promoter activity.