Mannan binding lectin (MBL) deficiency in upper respiratory tract infections of a pediatric population

Non clonal or innate immune system plays a key role in the immediate response to infections. This is important during the window of vulnerability experienced by all infants following the waning of passive protection prompted by maternal antibodies. The complement system is an integral part of the innate immune system. A new C activation pathway is initiated by the binding of mannan binding lectin (MBL) to carbohydrates. MBL is structurally related to the complement Clq and to collectins, and seems to activate the C through two associated serine pretenses known as MASP I and 2, which are similar to Clr and Cls of the classical pathway. MBL binds to certain carbohydrate structures of many microorganisms and exhibits antibacterial activity through killing mediated by terminal, lytic complement components ol by promoting opsonization and phagocytosis, The plasma concentration of MBL is genetically determined, and low serum concentration could be associated with frequent infections in childhood. We now report a significant correlation between the low serum MBL concentration and susceptility to upper respiratory tract infections in a pediatric population. 2/29 individuals affected by recurrent tonsillitis vs 1/171 controls (p < 0,05 by exact Fisher's test) were found with low serum MBL concentration. Moreover 9/29 patients versus 44/236 controls had C4 null alleles (p = 0.04 by exact Fisher's test). Primary immunodeficiencies early diagnosis could be important because a prompt treatment of infections helps avoiding complications proving life saving in certain instances. Appreciation of me genetic nature of a host defence defect makes possible family counseling, where indicated and a better understanding of the role of each factor in establishing immune system equilibrium.