Primary BUiary Cirrhosis Immunol Res 1992;11:98-103
M. Schlesinger a C. Benbassat b Y. Shoenfeld b
The Clinical Immunology Unit, Barzilai Medical Center, Ashkelon, and Ben-Gurion University of the Negev, Beer-Sheva, Israel; b Department of Medicine B, Chaim Sheba Medical Center, Tel-Hashomer, and Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
W J ~ O B , O O O O , t . . . B ~ 1 7 6 1 7 6 1 7 6 1 7 6
Key Words Primary biliary cirrhosis Antimitochondrial antibodies complement Acute phase reaction Autoimmunity
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Abstract PBC is a chronic progressive liver disease of unknown etiology. Several abnormalities found in PBC support the hypothesis that it may be considered an autoimmune disease. Despite the complex and interesting relationship that exists between autoimmune disorders and the complement system, very few reports on the level of the serum complement component in PBC have been published, and most of these comprised only a few patients or analyzed only a scant number of the complement components. In the present study, sera of 73 PBC patients were analyzed for the levels of 10 complement components. It was found that the levels of most of the serum complement components, including Clq, C2, C3, C5, C7, properdin and factor B were significantly elevated in patients with PBC in comparison to healthy controls. The level of C4 was slightly lower than that of the normal controls (p = 0.019), while the levels of C6 and C8 were within the normal range. The number of PBC patients with serum levels of C4 and C6 < 60% of normal pooled serum was higher than in the respective control groups (6/69 compared with 0/26 and 4/71 compared with 0/27, respectively). However, the difference was not statistically significant. Thus, our study shows alterations in the levels of most complement components in PBC, the reasons for which are discussed.
Introduction Primary biliary cirrhosis (PBC) is a chronic liver disease of unknown etiology, characterized by patchy granulomatous inflammation and destruction of small intrahe-
patic bile ducts, leading to progressive cholestasis and cirrhosis [1 ]. Several immunological abnormalities found in PBC support the hypothesis that autoimmune mechanisms are involved in its pathogenesis. Firstly, more than 80% of the patients have other associ-
Dr. Y. Shoenfeld Sheba Medical Center Department of Medicine B Tel-Hashomer 52621 (Israel)
9 1992 S. Karger AG, Basel 0257-277X/92/ 0112-009852.75/0
ated autoimmune disorders . Secondly, antimitochondrial (anti-pyruvate dehydrogenase) autoantibodies are found in more than 90 % of patients , and other autoantibodies, such as antinuclear antibodies, antismooth muscle antibodies or antithyroid antibodies, are also frequently detected [4, 5]. In addition, hypergammaglobulinemia with quantitative and qualitative abnormalities of IgM , together with the presence of circulating immune complexes, were reported in PBC by several investigators [7, 8]. Defective C3b receptor-mediated clearance function of Kupffer cells, similar to other autoimmune diseases, has also been described . Despite the strong relationship that exists between autoimmune disorders and the complement system, very few studies have been done up to now regarding the role of the complement system in PBC. Moreover, these studies analyzed a limited number of complement components and generally included only a small number of patients. For example, there is only one report (comprising 20 patients) on serum properdin levels, and the levels of the late components (C5-C9) in PBC have so far not been studied. The purpose of this study was to conduct a comprehensive analysis of the levels of the various complement components in 73 patients with PBC.
Patients and Methods The patients with PBC were chosen randomly from a pool at the Chaim Sheba Medical Center. In all the patients the diagnosis of PBC was conform histologically in association with antimitochondrial antibodies. Normal serum levels of complement obtained from 27 healthy donors were used as control. Blood was aspirated and left to clot at room temperature for 1 h, and the serum was then separated after centrifugation at 4 ~ The sera were kept in aliquots at - 8 0 ~ until tested. A normal serum pool composed of a mixture of
sera from 15 normal volunteers was also prepared and kept in the same manner. The results were expressed as a percent of the normal sera. Radial immunodiffusion  was performed in 1% agarose gels containing monospecific goat antibodies to human complement components. Analysis of statistical significance between the groups was performed using Student's t test and the Xz test. p < 0.05 was considered significant.
The mean (__ SD) serum levels of the various complement components tested in the PBC patients and the controls is summarized in table I. As can be seen, the mean serum concentrations of most complement components are significantly higher in PBC patients than in normal subjects. The mean concentrations of Clq, C2, C3, C5, C7 and properdin in the serum of PBC patients are between 144 and 250% of the normal pooled sera, while the mean concentrations of the respective healthy controls are in the range of 110132%. The mean serum concentration of factor B in the PBC patients is only 122 % of the normal pooled sera, but this level is significantly increased when compared to the serum concentration of the respective normal controls (p -- 0.001). In contrast, the concentrations of C4, C6 and C8 were not elevated in the PBC group, and the mean level of C4 was even lower in PBC patients than in normal subjects (p = 0.019). However, when the six sera with the very low C4 concentrations ( < 60%) were excluded (fig. 1), the mean serum level of C4 was 119 %, which is not significantly different from that in the control group (mean -- 132 %; p = 0.07). The serum levels of C4 and C6 (fig. 1, 2) were found to be < 60% in some of the PBC patients but in none of the healthy controls (6/69 and 4/71 patients vs. 0/26 and 0/27 healthy controls, respectively), although these
differences are not statistically significant (p -0.28 and p = 0.5, )~2 test). However, except for another 3 patients with mildly decreased levels of C5, C7 and C8 (53, 54 and 59%, respectively), no other complement components were found to be lower than 67% of the normal in both the PBC and the control groups.
There is a complex relationship between autoimmune disorders and the complement system. Firstly, many of the clinical manifestations of autoimmune diseases are of the inflammatory type, and since some complement components may act as acute-phase reactants, their synthesis might be expected to be increased [1 1]. Secondly, immune complex diseases can activate the complement system, which in turn mediates the inflammatory process and tissue damage. As a result of complement activation, there is increased consumption, lowering of serum complement component levels, and an increase in circulating con-
version products. In addition, autoimmune diseases are known to be associated with the major histocompatibility complex including with those genes coding for C2, C4 and factor B. Several studies report a strong association between some C2 and C4 allotypes and some autoimmune disorders like systemic lupus erythematosus [ 12] and scleroderma [ 131. Finally, there is a high incidence of autoimmune disorders among patients with hereditary deficiency of the early complement components (e.g., C2, C4). One reason for this could be the defective immune complexes formed in the absence of certain complement components [14, 151. It can be expected therefore that abnormal complement component levels will be found in PBC. However, in contrast to the many reports on the profile of the complement system in several autoimmune diseases, very few studies have analyzed the complement system in PBC, and most of them included only a scant number of patients. The results of these studies are summarized in table 2. One additional study by Wands et al. [I 6], which ana-
Table 1. Complement component levels in PBC
Clq C2 C3 C4 C5 C6 C7 C8 FB Prop.
mean • SD
mean • SD
66 70 72 69 73 71 73 72 69 72
144• 157• 173• 113• 196• 102 110• 250• 109 105• 19 122• 180•
25 27 20 26 27 27 24 25 17 24
110• 115• 121 • 132• 122• 112• 19 126• 113• 32 92• 132•
131 136 143 86 161 98 198 93 133 136
0.0002 0.000 0.0001 0.019 0.0004 NS 0.0000 NS
SD = Standard deviation; NS = not significant; FB = factor B; Prop. = properdin.
Primary BiliaryCirrhosis and Complement
200 220 180
Fig. 1. C4 levels in PBC patients and normal controis. Levels of C4 are expressed in percentage of pooled normal sera. The solid line represents the mean value. The concentration of C4 in 6 PBC patients is