Correlation between serum immunoglobulin concentrations and smooth-muscle antibodies in acute viral hepatitis

Smooth-muscle antibodies (SMA) were investigated by the indirect immunofluorescence method and serum immunoglobulin (Ig) concentrations measured by radial immunodiffusion in 15 patients with hepatitis B antigen (HBAg)-positive and 20 patients with HBAg-negative acute hepatitis. In both types of hepatitis the serum IgM and IgG concentrations were significantly higher than in 55 controls, while the IgA levels were the same in patients and controls. IgM-SMA in titres of 10--80 occurred in 11 (55%) patients with HBAg-negative acute hepatitis, and this was significantly higher than in controls (P = 10(-8), whereas IgM-SMA were found in only 2 (13%) patients with HBAg-positive acute hepatitis. IgG-SMA occurred in 3 (15%) HBAg-negative and in 4 (27%) HBAg-positive patients. In HBAg-negative hepatitis the serum IgM concentrations were significantly higher in IgM-SMA-positive (mean: 439 mg/dl) than in IgM-SMA-negative (mean: 216 mg/dl) cases (P = 0.028). It was not possible to demonstrate a similar rleationship in HBAg-positive acute hepatitis. No correlation between the occurrence of IgG-SMA and the IgG levels could be demonstrated in acute hepatitis. It is assumed that IgM-SMA may account for a minor part of the elevated IgM levels in HBAg-negative acute hepatitis, but the reason for formation of SMA in acute viral hepatitis is not known.