Studies of smooth-muscle antibodies in acute hepatitis.

Smooth-muscle antibodies (SMA) of the IgG and IgM class in titres of 10 to 80 were demonstrated in 19 of 38 patients with acute hepatitis (50 per cent). No IgA-SMA were detected. IgM-SMA occurred in the beginning of the disease, while IgG-SMA were found both early and late in the course of disease. There was no correlation between the occurrence of SMA and the biochemical liver parameters or the mode of exposure to infection, but IgM-SMA were found more often in the first serum sample obtained from patients without hepatitis-B-associated antigen (HBAg) than in HBAg-positive patients (P1 + P2 = 0.04) and it is suggested that hepatitis virus A more readily than hepatitis virus B can elicit the formation of SMA. The mean PHA-induced lymphocyte-transformation response was significantly lower in hepatitis patients than in the controls (0.02 greater than p greater than 0.01). The lymphocyte-transformation response to a low PHA dose (1 mug per ml) was lower in hepatitis patients without SMA than in those with SMA (0.10 greater than p greater than 0.05). SMA were not found in 28 control persons, and the incidence of tissue antibodies other than SMA did not differ in hepatitis patients and controls.