The human chemokine receptor CXCR-1 (or IL8R-alpha) is a specific receptor for the chemokine interleukin 8 (IL-8) . Initially identified as a chemoattractant for neutrophils, IL-8 has been demonstrated to have pro-inflammatory effects including stimulation of neutrophil degranulation . Cellular activities of IL-8 are mediated by CXCR-1 and CXCR-2 (IL8R-beta), which maintain 78% of amino acid similarity and are encoded by two single-copy genes that are located on chromosome 2q34-35 . However, CXCR-1 is more specific for IL-8 in comparison with CXCR-2 .
The involvement of IL-8, CXCR-1 and CXCR-2 has been extensively investigated in different diseases such as pyelonephritis [5, 6], hepatitis B , rapid disease progression of HIV-1+ , lung diseases, such as chronic obstructive pulmonary disease and asthma , bronchiectasis , systemic sclerosis  and lung cancer . Some of these studies have reported positive associations between the diseases and single nucleotide polymorphisms (SNPs) in the CXCR1 gene [8, 9]. Indeed, a significant association was demonstrated between the 860G > C (S276T) SNP in the CXCR1 gene with decreased lung cancer risk . Haplotypes formed by SNPs in the CXCR1 and CXCR2 genes where also previously identified .
The 860G > C (S276T) SNP in CXCR1 gene was identified by comparison of multiple sequences deposited in the GenBank/EMBL data banks [11, 13]. These authors named this polymorphism differently: +2607 (position 6334 of sequence accession number [GenBank: L19592.1]) in exon 2, and +827 (starting from the initiation of the ATG codon in exon 2 of [GenBank: L19592.1]), respectively. The variant position 860G > C is based on the [NCBI: NM000634.2] exon 2 initiations, however it is important to be clear that all these different positions at the CXCR1 gene refer to the same polymorphism (G > C), which results in a conservative amino acid substitution from serine to threonine at the 276 amino acid residue of the CXCR-1 (or IL8R-alpha) protein. Here, we preferred to use the reference sequence number [refSNP ID: rs2234671] in NCBI's Entrez system (http://www.ncbi.nlm.nih.gov/SNP).
Predominantly in the last decade, many candidate-gene investigations have been conducted in order to find genetic risk factors associated with chronic periodontitis (CP). Epidemiological studies indicate that CP is an important cause of teeth loss in adults, since 5% to 15% of any population suffers from this disease . CP is a multifactorial disease, initiated by bacterial infection which can progress to the damage and destruction of the supporting tissues of the teeth . The host response is influenced by both environmental (e.g. smoking, oral hygiene) and genetic factors . Some studies have demonstrated association between polymorphisms in genes of the immune system and CP, such as Interleukin 2 (IL2) [17, 18], IL4 [19–21], IL6 [22, 23] and IL10 [24, 25]. Recently, we have reported association between haplotypes in the IL8 and in the CXCR2 genes with CP [26, 27]. Because those previous findings and the biological relationship of the CXCR-1 with the IL-8 and the CXCR-2 [1, 5] we have hypothesized whether a SNP in the CXCR1 gene would also influence the host susceptibility to CP.
In this regard, the aim of this study was to investigate the association of the rs2234671 SNP in the CXCR1 gene in a Brazilian population with chronic periodontitis.