tokens: These data demonstrate that 1 ) type I human complement C2 deficiency is caused by a 28 - base pair genomic deletion that causes skipping of exon 6 during RNA splicing , resulting in generation of a premature termination codon , 2 ) the 28 - base pair deletion in the type I C2Q0 gene is strongly associated with the HLA haplotype / complotype A25 , B18 , C2Q0 , BfS , C4A4 , C4B2 , Drw2 , suggesting that all C2 - deficient individuals with this haplotype / complotype will harbor the 28 - base pair C2 gene deletion , and 3 ) type II C2 deficiency is caused by a different , as yet uncharacterized , molecular genetic defect . .