MBL2 and chronic obstructive pulmonary disease: In order to test if MBL genotypes of exon 1 alleles are associated with COPD outcomes (exacerbation frequency), we grouped the genotypes into two: where the MBL2 polymorphisms 52 (A/D), 54 (A/B), and 57 (A/C) alleles can be grouped and referred as genotype “O” that is considered to express low serum MBL, while the other alleles were assigned as genotype “A” that express normal serum MBL levels [16].