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Mannose-binding lectin (MBL) is a protein of innate immune system that is involved in opsonization and complement activation. MBL deficiency is associated with predisposition to infectious diseases; however subnormal levels are also seen in healthy subjects. The aim of this study was to investigate the prevalence and clinical manifestation of MBL deficiency in patients with increased susceptibility to infection. We studied the MBL serum concentration of 104 patients with a history of recurrent and/or severe infections referred to Immunology, Asthma and Allergy Research Institute (IAARI) in order to evaluate the primary immunodeficiency (PID). The distribution of MBL deficiency in these patients and 593 healthy subjects of previous study were analyzed. The frequency of individuals with MBL deficiency was significantly higher in patients with recurrent and/or severe infections (13.5% [14/104]) compared with healthy subjects (4.7% [28/593]; p=0.001; OR 3.1, 95% CI 1.5-6.1). However, in 10.9% (7/64) of patients with recurrent infections without any immunodeficiency background, the MBL deficiency was detected. On the whole, our findings indicate an association between MBL deficiency and increased susceptibility to infections.

Mannose-binding lectin (MBL) is a Ca⁺² -dependent collagenous lectin, that is produced by liver and mediates innate immune responses by opsonization of pathogens. The serum level of MBL varies widely among healthy individuals, ranging from 0.05 µg/ml (or lower) to over 5 µg/ml, mainly depending on genetic variation. This study has examined promoter and exon 1 of mbl2 genotype among 117 Iranian healthy blood donors. MBL Single Nucleotide Polymorphisms (SNPs) were genotyped using polymerase chain reaction (PCR), and serum levels of MBL were quantified using a double-antibody enzyme linked immunosorbent assay (ELISA). Results of this study showed that there are two promoter polymorphisms at -550 (H/L variants) and -221 (Y/X variants) positions, and three polymorphisms in exon 1 at codon 52 (D Allele), 54 (B Allele), and 57 (C Allele) in this population. B allele was significantly correlated with the lowest serum MBL level. Our results also showed that the most frequent genotype was HYA/LXA, and the genotype that associated with the highest serum level of MBL was HYA/HYA. The genotype that causes lowest MBL production in Iranian population was LYB/LXA. These results showed some differences compared to that of the other populations. To verify the originality of these differences we may need to extend the study to a larger samples of respective populations; meanwhile the importance of a new mutation, nucleotide 101 of MBL2 exon1, reported in the current study should be taken in considerations in terms of its possible pathobiological effects in following studies.

Mannan-binding lectin (MBL) is a vital protein of innate immune system and has two critical functions: complement activation through the lectin pathway and opsonization. MBL deficiency has been classified as the most common inherited immunodeficiency known in humans (about 30% of the population), and is associated with predisposition to infections and high risk of some autoimmune diseases. The purpose of this study was to determine the profile of MBL serum level in Iranian healthy population in association with sex and age groups for the first time. We studied the serum concentration of MBL in 593 Iranian healthy cases: 340 males and 235 females in 4 different age groups by using enzyme-linked immunosorbent assay. The mean serum levels of MBL were 3.854 ± 2.77 µg/ml at the age of less than 6 months, 4.147 ± 3.54 µg/ml at 6 months to 2 years of age, 4.410 ± 3.09 µg/ml at 2-6 years and 2.207 ± 1.73 µg/ml in adults. There was significant differences in the mean concentration of MBL among different age groups of children and also between children and adults (p<0.05). No association was observed between sex and MBL concentrations. MBL serum levels of Iranian population seem to be different from some of other populations which may be explained by genetic variations. The MBL values in this study can be used as a normal reference range for future studies in Iranian population.