Assessment of Toll like Receptor 2 Gene Polymorphism in Children with B Cell Defects and Respiratory Tract Infections

Abstract

Acute respiratory tract infections are the most common illnesses in childhood, comprising as many as 50% of all illnesses in children less than 5 years old and 30% in children aged 5-12 years. Multiple factors determine the frequency and nature of these illnesses, these include host factors, environmental factors and infecting agents (Bryce et al., 2005). Toll-like receptors (TLRs) are a class of proteins that play a key role in pathogen recognition and initiation of innate immune response and promote adaptive immunity (Medzhitov, 2001 ;Unterholzner et al., 2010). They represent a primitive defense mechanism against bacteria, fungi and viruses, and play a key role in inflammation initiation and consequent immune response (Akira et al., 2001). Currently, more than 10 kinds of TLRs have been identified (TLR1-10), and each is devoted to recognizing a distinct set of molecular patterns (Atmaca et al.,2014). Growing amounts of data suggest that the ability of certain individuals to respond properly to TLR ligands may be impaired by single nucleotide polymorphisms (SNPs) within TLR genes, resulting in an altered susceptibility to, or course of, infectious or inflammatory disease (Misch and Hawn, 2008) as in TLR2 gene polymorphisms Arg677Trp and Arg753Gln as can be observed in patients with sepsis from gram +ve microorganisms (Moore et al., 2004;Texereau et al., 2005). Patients with Primary immunodeficiency are more susceptible to infections of any kind, including respiratory tract infections which lead to permanent lung damage in 20-40% of patients. Although pulmonary complications are diverse, bronchiectasis is the most severe complication of recurrent respiratory infections in hypogamma-globulinaemic patients, which can occur despite apparently appropriate Ig replacement (Bonilla et al., 2005).