Low levels of mannose-binding lectin confers protection against tuberculosis in Turkish children

Mannose-binding lectin (MBL) plays an important role in innate immunity mediating phagocytosis and activating the MBL complement pathway. Few studies, conducted in adult populations, have shown that genetically determined low MBL levels may confer partial protection against tuberculosis (TB). In this study we aimed to investigate the relationships between the susceptibility to TB and two low producing MBL2 gene polymorphisms (codons 54 and 57) and MBL levels in children. Forty-four TB children (27 pulmonary TB, 17 extrapulmonary TB) and 99 age-matched healthy control children were included in the study. The mean age in the study group was 7.02 ± 4.5 years. Genotyping of the MBL2 gene for codon 54 and 57 polymorphisms was carried out, and MBL levels in serum were also detected in all subjects from both groups. None of the subjects from either group showed codon 57 polymorphisms. The frequency of the AB genotype which produces low level MBL is significantly lower in the patients (9.1%) compared to control subjects (27.3%) (p < 0.011). The difference was especially significant between the extrapulmonary group and healthy controls (p < 0.006). The BB genotype was observed in only one child from the healthy controls and no children from the patient group. The median MBL plasma concentration was also significantly lower in the control group than that found in the study group (p = 0.036). These results indicate that low levels of MBL and AB genotype may be involved in the protection against tuberculosis, especially extrapulmonary tuberculosis in children.