Microheterogeneity of acute-phase glycoproteins in patients with pulmonary sarcoidosis

This study was designed to investigate qualitative changes in the carbohydrate side-chains of two acute-phase glycoproteins, alpha 1-acid glycoprotein (AGP) and alpha 1-antichymotrypsin (ACT), in 37 patients with pulmonary sarcoidosis. The glycosylation profile of AGP and ACT was studied using affinity immunoelectrophoresis with the lectin concanavalin A (conA). Serum concentration of soluble receptor for interleukin-2 (sIL-2R) and activity of serum angiotensin converting enzyme (ACE) were measured by specific enzyme-linked immunosorbent assay (ELISA) and enzyme kinetic assay, respectively. Rocket immunoelectrophoresis and nephelometric assay were used to determine serum concentration of AGP, ACT and C-reactive protein (CRP). In 11 patients with active disease, a decreased reactivity of AGP with conA was found as compared with controls (n = 44) and patients with nonactive sarcoidosis (n = 26). A similar tendency was seen with ACT. In the same group, increased concentrations of serum AGP and higher levels of sIL-2R were detected compared with patients with nonactive sarcoidosis. In the entire sarcoidosis group, there was a negative correlation between ACE activity and AGP and ACT affinity for conA (r = -0.6358, and r = -0.5019, respectively) and a positive correlation with sIL-2R level (r = 0.8241). In nine patients with elevated concentrations of serum CRP, no differences were found in disease activity and glycosylation profile of AGP and ACT when compared to patients with normal serum CRP. The results suggest that in active pulmonary sarcoidosis changes in the glycosylation pattern of acute-phase glycoproteins exist, which are similar in trend and magnitude to those found in other chronic inflammatory diseases. The synthesis and glycosylation of acute-phase proteins in pulmonary sarcoidosis are probably regulated independently.