Predictive value ofIgGautoantibodies against C 1q fornephritis insystemic lupus erythematosus

Objectives-Antibodies againstClq (CIqAb)havebeendemonstrated inthe serumofpatients withseveral immune complexdiseases. Patients, particularly thosewithlupusnephritis, werefoundto haveincreased serumtitres ofIgGClqAb in a cross-sectional analysis. In the presentprospective studycorrelations weresoughtbetweenserumtitres ofIgG ClqAbandclinical aswellaslaboratory parameters ofdisease activity inpatients with systemiclupus erythematosus (SLE). Methods-Titres ofIgG ClqAb inthe serumof68SLEpatients weremeasured serially during athree yearperiod. Atthe sametimeclinical andlaboratory parametersofdisease activity wereassessed. Results-Increased titres ofIgGClqAb were foundin theserum of 56% of SLEpatients during thestudy. Significant correlations were found between increased titres ofIgGClqAbandrenal involvement. Clinical signsof renal involvement werefoundtobeassociated withsignificant increases ofserumtitres ofIgGClqAbinthesixmonthspreceding thisappearance. Fifty percentofthe increases inserumtitres ofIgGClqAb werefollowed bythedevelopment ofrenal involvement. Elevated serum titres of IgGClqAbwere especially related to proliferative formsofglomerulonephritis. Furthermore, significant correlations werefoundbetweenserumtitres ofIgG ClqAb and serum levelsof immune complexes, levels ofcomplement components, andtitres ofantibodies toDNA. Conclusions-The results suggest thatIgG ClqAbplaya pathogenic rolein the development oflupusnephritis andthat serial measurementofserumtitres ofIgG ClqAbisuseful inthemanagementof SLEpatients.