The relationship between serum titers of autoantibodies to C1q and age in the general population and in patients with systemic lupus erythematosus.

The aim of the present study was to assess the relationship between age and titers of autoantibodies to C1q (C1qAb) in individuals randomly selected out of the general population and in systemic lupus erythematosus (SLE) patients. Serum samples of 659 randomly selected individuals and 169 SLE patients were divided into 6 age groups from 20 to 79 years. IgG and IgA C1qAb titers were measured by ELISA. The highest titers of IgG and IgA C1qAb in sera of randomly selected individuals were found in the oldest age groups. In serum of SLE patients the highest titers of IgG C1qAb were found in the youngest age groups, whereas IgA C1qAb titers did not change with aging. It is concluded that the distribution pattern of IgG and IgA C1qAb titers in serum of individuals randomly selected out of the general population is similar to that of other autoantibodies. The increased titers of IgG C1qAb in serum of young patients with SLE suggest a role of these antibodies in the pathogenesis of the disease.