Background: Immunoglobulin A is the predominant immunoglobulin in the bile. Data on the effects of biliary obstruction on IgA secretion are few.

Methods: The serum and bile IgA levels in patients with common duct stones (n = 27) or with malignant obstructive jaundice (n = 20) were collected by insertion of nasobiliary catheters. Single samples of common duct bile from patients with gallstones (n = 24) were collected as controls. Bile samples collected were measured for total IgA, secretory IgA, and free secretory component levels by sandwich enzyme-linked immunosorbent assays.

Results: Bile total IgA, secretory IgA, and free secretory component in the common duct stones group (82.7 ± 11.4 μg/ml, 18.4 ± 1.7 μg/ml, 0.74 ± 0.15 μg/ml) and the malignant obstructive jaundice group (81.6 ± 10.7 μg/ml, 18.2 ± 2.4 μg/ml, 0.57 ± 0.12 μg/ml) were found to be significantly lower than those of the control gallstone patients (104.8 ± 3.4 μg/ml, 33.2 ± 2.9 μg/ml, 1.03 ± 0.12 μg/ml) (P < 0.05). Serum secretory IgA levels in the common duct stones (26.53 ± 1.75 μg/ml) and malignant obstructive jaundice groups (26.03 ± 3.48 μg/ml) were significantly higher than the gallstone group (18.45 ± 4.56 μg/ml). The bile-to-serum concentration ratio of total IgA, secretory IgA, and free secretory component levels rose significantly within 48 hours after relief of obstruction.

Conclusions: Biliary obstruction secondary to both calculus or malignancy of the hepatobiliary system causes suppression of bile IgA secretion and elevated serum level of secretory IgA. Bile secretory IgA secretion recovers with endoscopic drainage of the obstructed system. (Gastrointest Endosc 1995;42:439-44.)