Abstract: Background: Vitamin D and vitamin D dependent antimicrobial peptides such as Cathelicidin (LL-37) and
?-defensin 2 have an important role in innate and adaptative immunity, but their role in pleural effusions has not
been studied before.
Methods: Serum and pleural fluid samples from 152 patients with pleural effusion were collected, corresponding to
45 transudates and 107 exudates, 51 infectious effusions (14 complicated and 37 non-complicated), 44 congestive
heart failure effusions and 38 malignant effusions. The levels of 25 OH-vitamin D, 1,25-(OH)2-vitamin D, Vitamin D
Binding Protein (VDBP), LL-37 and ?-defensin 2, both in serum and pleural fluid were evaluated in this prospective
study. Differences between groups were analysed using unpaired t tests or Mann?Whitney tests. Correlations
between data sets were examined using Pearson correlation coefficient or Spearman rank correlation coefficient.
Diagnostic accuracy was estimated using ROC curve analysis.
Results: Low serum 25 OH vitamin D levels were found in all groups. Infectious effusions (IE) had higher serum and
pleural fluid LL-37 levels compared to congestive heart failure or malignant effusions. Among IE, complicated had
higher serum and pleural fluid LL-37 levels, and lower serum ?-defensin-2 levels. Positive correlations were found
between serum 25 OH-vitamin D levels and serum or pleural 1,25-(OH)2-vitamin D levels, and between 1,25-(OH)
2-vitamin D and LL-37 serum. Diagnostic accuracy of the different molecules was moderate at best.
Conclusions: Hypovitaminosis D is highly prevalent in pleural effusions. LL-37 is produced intrapleurally in IE.
This production is higher in complicated IE. No evidence of pleural production of ?-defensin 2 was found in
any of the groups. Diagnostic accuracy of the different molecules is at the best moderate for discriminating
different types of effusions.
