The effect of anti‐CD40 ligand antibody on B cells in human systemic lupus erythematosus

Abstract

Objective To determine the immunologic effects of anti–CD40 ligand (anti-CD40L) therapy in 5 patients with systemic lupus erythematosus nephritis who participated in an open-label study of a humanized anti-CD40L monoclonal antibody. Methods Serum and peripheral blood mononuclear cells were obtained before, during, and after treatment, and the frequency of Ig and anti-DNA antibody–secreting B cells was analyzed by enzyme-linked immunospot assay and by analysis of Epstein-Barr virus (EBV)–transformed B cell lines. To determine the effect of treatment on somatic mutation of Ig genes, reverse transcriptase–polymerase chain reaction was performed on messenger RNA from 4 patients, using primers specific for the DP-47 heavy chain gene and for IgG. Finally, B cell phenotype was investigated using flow cytometry. Results Even a brief period of treatment with anti-CD40L markedly reduced the frequency of IgG and IgG anti-DNA antibody–producing B cells, and these changes persisted for several months after cessation of treatment. To confirm these findings, EBV-transformed B cell lines were screened from each of 3 patients, and a 10-fold decrease in anti-DNA antibody–secreting cell lines was found after treatment in all 3 patients. Few differences in mutation patterns were observed before and after treatment; however, the frequency of germline-encoded DP-47 sequences was significantly increased before treatment and normalized following treatment. Flow cytometric analysis of B cells revealed expansion of a CD27−/IgD− B cell subset in some of the patients, which did not change with treatment. Conclusion These are the first mechanistic studies of the effect of anti-CD40L therapy in human autoimmune disease. The results suggest that further studies of CD40L blockade are warranted.