Evaluation of soluble CD 14 and neopterin as serum parameters of the inflammatory activity of pulmonary sarcoidosis

Abstract

CD14 represents the most specific marker for monocytes/macrophages. It has been demonstrated in vitro that monocytes/macrophages lose this antigen upon activation. Results of studies investigating the expression of membrane-bound CD14 on the surface of monocytes/macrophages in sarcoidosis patients are controversial. To investigate whether the soluble form of CD14 reflects monocyte/macrophage activation in sarcoidosis, serum levels of soluble CD14 were determined concurrently with other serum markers of monocyte/macrophage activation (neopterin, angiotensin-converting enzyme) in 50 consecutive patients with bioptically confirmed sarcoidosis. The patients were allocated to three groups according to disease activity and therapy. The soluble interleukin-2 receptor in serum and the CD4/CD8 ratio in lavage fluid were used to monitor T-lymphocyte activation. No significant differences in serum or bronchoalveolar lavage levels of soluble CD14 were observed in patients with active or inactive sarcoidosis. Despite the presence of normal soluble CD14 serum concentrations a correlation with serum neopterin and angiotensin-converting enzyme was found in active sarcoidosis (soluble CD14 versus neopterin, rs = 0.61 and 0.65, P < 0.05 and 0.01, respectively; soluble CD14 versus angiotensin-converting enzyme, rs = 0.6 and 0.72, P < 0.02 and 0.003, respectively). A correlation between soluble CD14 and parameters of T-cell activity was not demonstrated. We therefore conclude that soluble CD14 in serum is not a useful clinical parameter in establishing disease activity in sarcoidosis. Neopterin and angiotensin-converting enzyme serum concentrations are parameters with higher sensitivity, although specificity remains very low. The exact role of CD14 antigen in sarcoidosis requires further investigation.