MANNOSE-BINDING LECTIN (MBL) GENE POLYMORPHISMS AND SERUM MBL LEVELS IN CHILDREN WITH RECURRENT RESPIRATORY TRACT INFECTION

Abstract

INTRODUCTION: Mannose-binding lectin (MBL) is a plasma collectin and is considered an important component of innate immunity. Its plasma concentration is, for the most, part genetically determined by a series of single nucleotide polymorphisms located both in the structural gene and in the promoter region. MBL deficiency may be associated with increased susceptibility to infectious disease and autoimmune disorders. OBJECTIVE: Our goal was to establish the reference serum level of MBL in children, investigate the correlation between MBL gene polymorphisms and its serum level in Chinese Han nationality, and MBL gene polymorphisms and serum level in children with recurrent respiratory tract infections. METHODS: The concentrations of oligomerized MBL in plasma were measured by enzyme-linked immunosorbent assay, and MBL gene polymorphisms were analyzed by polymerase chain reaction-restriction fragment length polymorphism and polymerase chain reaction with sequence-specific primers. RESULTS: The median MBL level in 470 normal children was 2536 ng/mL (range: 0–7860 ng/mL), and P2.5 to P97.5 was 161 to 5070 ng/mL. Two promoter polymorphisms, -550 and -221, and coding variants at codon 54 of the MBL gene affected the protein level significantly, and the most frequent genotype in Hans was HYPA/HYPA. Serum MBL levels were significantly lower in patients with recurrent respiratory tract infections (RRTIs) compared with healthy controls (H = 6.661; P < .05), and the frequency of the promoter LXP haplotype was significantly higher in patients with RRTIs than in controls (χ2 = 4.71; P = .03). The prevalence of the B allele in patients with RRTIs was higher than that in controls, but the difference did not reach significance (χ2 = 0.18; P > .05). CONCLUSIONS: The MBL reference value in China is 161 ng/mL. Children with MBL concentrations of <161 ng/mL, therefore, were deemed to be MBL deficient, and LXP is a risk factor for recurrent respiratory tract infections in this population.