Background: Surfactant Protein D (SP-D) is a pattern recognition molecule belonging to the collectin family expressed in multiple human organ systems including the lungs. Previous studies have shown that SP-D concentrations in bronchoalveolar lavage samples decreases and serum concentrations increases in patients with asthma possibly attributable to a combination of induced SP-D synthesis and decreased air-blood barrier integrity. The aims of this study were to investigate if the serum level of SP-D and common variations in the SP-D gene were associated to asthma in adolescents and young adults. Methods: Prospective observational study including 449 adolescents and young adults (age 11-27 years) previously diagnosed with asthma during a two-year period from 2003 to 2005 (0-16 years). At follow-up from 2016 to 2017 314 healthy controls with no medical history of asthma were recruited. Serum SP-D was analyzed on samples obtained at baseline as well as samples obtained at follow-up. SP-D genotyping was performed for rs721917, rs2243639 and rs3088308. Results: No differences were found in mean levels of sSP-D and SFTPD genotype among subjects with current asthma, no current asthma and controls. Serum SP-D and SFTPD genotype were not associated to any clinical parameters of asthma. Furthermore, baseline sSP-D was not associated to asthma at follow-up. Conclusion: Serum surfactant protein D and common SP-D gene variants were not associated with asthma in Danish adolescents and young adults with mild to moderate asthma. Serum surfactant protein D did not demonstrate any value as a clinical biomarker of asthma.

Background: Previous studies have investigated the natural course of cow’s milk protein allergy (CMPA) and development of atopic diseases into adolescence. Studies with long term follow-up into adulthood are lacking. The aim of this study was to investigate 1) the natural course of CMPA in a 1-year birth cohort of Danish children from birth until 15 and 26 years of age and 2) the development of atopic diseases in a group of children with CMPA (group A) compared to a random sample of 276 children from the same birth cohort (group B). 
Methods: A birth cohort of 1,749 newborns, was investigated prospectively for the development of CMPA and atopic diseases. During the first year of life and at 18 months and 3, 5, 10, 15, and 26 years of age, questionnaire based interviews, physical examination, skin prick tests and specific IgE testing, and from 10 years also spirometry, were carried out. 
Results: 39 (2,2%) were diagnosed with CMPA. The recovery rate was 87%, 92% and 97% at 3, 5 and 26 years of age. Compared to group B, group A had significantly (p < 0,05) higher prevalence of asthma and rhinoconjunctivitis at 15 years of age and at 26 years of age, group A had significantly higher prevalence of asthma and atopic dermatitis. The follow-up rate was 85% (A) and 70% (B). 
Conclusion: CMPA has a good prognosis regarding recovery rate. CMPA and sensitization in early childhood predict sensitization and persistence of allergic diseases into adulthood.