All DNA samples were genotyped for four SNPs, namely C1QA rs292001, C1QB rs913243, rs291982 and rs631090. C1QA rs292001, C1QB rs291982 and rs631090 SNPs were genotyped by polymerase chain reaction with sequence-specific primers (PCR-SSP) under the conditions described elsewhere [25]. All primers for PCR-SSP were designed using the genomic sequences in the GenBank (http://www.ncbi.nlm.nih.gov, GenBank ID:712, 713). The primer sequences for three mentioned SNPs were as follows: 1) rs292001: allele G, reverse 5'GAT GCC CGG ATG CAA ATT AC, allele A, reverse 5'GAT GCC CGG ATG CAA ATT AT, constant forward 5'AGG CTT CAG AGA CTC ACA TTC; 2) rs291982: allele T, reverse 5'ACC TTT GCC CAG ATC CAA ATT, allele G, reverse 5'ACC TTT GCC CAG ATC CAA ATG, constant forward 5'AGC CAC AAG TCC CAA TGA GA; 3) rs631090: allele T, forward 5'CAC GGA TCT CTT ACC ATT AAA T, allele C, forward 5'CAC GGA TCT CTT ACC ATT AAA C, constant reverse 5'CAT CTG TGA AAT GGG GAT GAA. The presence/absence of allele-specific amplicons was visualized by 2% agarose gel stained with ethidium bromide fluorescence in reference to a molecular weight marker. Genotypes for C1QB rs913243G/T SNP were determined using TaqMan SNP genotyping assay (Applied Biosystems, Assay ID C_3176751_10) according to the manufacturer's instruction. Randomly selected samples (n = 45; 10% of the total number) were amplified twice to check for confidence of genotyping, and in each case complete concordance was obtained.