Low ficolin‐2 levels in common variable immunodeficiency patients with bronchiectasis

Summary Common variable immunodeficiency ( CVID ) encompasses a heterogeneous group of antibody deficiencies characterized by susceptibility to recurrent infections and sequelae, including bronchiectasis. We investigated the relevance of the lectin complement pathway in CVID patients by analysing ficolin‐2 and ficolin‐3 serum levels and genotyping single nucleotide polymorphisms ( SNP s) in the FCN 2 and FCN 3 genes. Our results show that ficolin‐2 levels in CVID patients are significantly lower ( P  < 0·0001) than in controls. The lowest ficolin‐2 levels are found in CVID patients with bronchiectasis ( P  = 0·0004) and autoimmunity ( P  = 0·04). Although serum levels of ficolin‐3 were similar in CVID patients and controls, CVID patients with bronchiectasis again showed lower levels when compared to controls ( P  = 0·0001). Analysis of single nucleotide polymorphisms in the FCN 2 gene confirmed known influences on ficolin‐2 serum levels, but did not support a genetic basis for the observed ficolin‐2 deficiency in CVID . We found that CVID patients with bronchiectasis have very low levels of ficolin‐2. The reason for the deficiency of ficolin‐2 in CVID and any possible causal relationship is currently unknown. However, as bronchiectasis is a very important factor for morbidity and mortality in CVID , ficolin‐2 could also serve as biomarker for monitoring disease complications such as bronchiectasis.