In lung transplant recipients (LTRs) severe clinical complications, as for instance acute cellular rejection or microbial infections of the lung, may occur. Surfactant protein D (SP-D) is a C-type lectin which is mainly produced in the lung and present in blood under physiological conditions only at low concentrations. Previous studies have shown that SP-D concentrations in blood may increase in distinct lung diseases.
Plasma samples routinely obtained from 58 LTRs either during periods without pathologic respiratory findings, or episodes of acute cellular rejection, microbial pneumonia, and microbial colonization of the transplanted lung, were investigated for SP-D levels, as well as samples from 29 healthy control persons. All samples were stored at the Department of Virology and plasma SP-D levels were measured with a commercially available enzyme linked immunosorbent assay (Bio Vendor, Heidelberg, Germany).
Median plasma SP-D concentrations from healthy controls and from LTRs without pathologic respiratory findings were comparable. In addition, no significantly increased median SP-D levels were observed in LTRs during episodes of microbial colonization and acute cellular rejection. In contrast, SP-D concentrations were in overall increased in plasma samples from LTRs obtained during microbial pneumonia (p<0.05).
Furthermore, LTRs with increased plasma SP-D concentrations during an episode of microbial pneumonia had a significantly higher risk to develop stage III bronchiolitis obliterans syndrome, to require retransplantation or to die in the subsequent 6 months (p=0.0093).
Increased plasma SP-D levels in LTRs observed during microbial pneumonia are significantly associated with the occurrence of severe clinical complications in the subsequent 6 months.