Natural antibodies targeting LPS in pleural effusions of various etiologies.

BACKGROUND:Respiratory infection, cancer and heart failure can cause abnormal accumulation of fluid in the pleural cavity. The immune responses within the cavity are orchestrated by leucocytes that reside in the serosal associated lymphoid tissue. Natural antibodies (NAbs) are abundant in the serum having a major role in systemic and mucosal immunity, however their occurrence in pleural fluid remains an open question. Our aim herein was to detect and measure the levels of NAbs targeting LPS of M, G, and A class in both, the pleural fluid and the serum of 78 patients with pleural effusions (PEs) of various etiologies. METHODS:The values of anti-LPS NAb activity were extracted through a normalization step regarding the total IgM, IgG and IgA levels and in addition the ratio of PF/S values were analyzed further with other critical biochemical parameters from biopsies. RESULTS:Anti-LPS NAbs of all Ig classes were detected in most of the samples, while a significant increase of anti-LPS activity was observed in infectious and non-infectious compared to malignant PEs. Multivariate linear regression confirmed a negative correlation of IgM and IgA anti-LPS PF/S ratio with malignancy. Moreover, anti-LPS NAbs PF/S measurements led to increased positive and negative predictive power in ROC curves generated for the discrimination between benign and malignant PEs. CONCLUSIONS:Our results highlight a potential role of anti-LPS NAbs in the pleural cavity that should be further explored.