Reduction of matrix interferences by the combination of chaotropic salt and DMSO in a broadly applicable target-based ELISA for pharmacokinetic studies of therapeutic monoclonal antibodies.

Use of a synergistic effect of DMSO together with a chaotropic salt (NaSCN or MgCl2) allowed to drastically reduce matrix interferences in an ELISA for therapeutic monoclonal antibodies. Optimum combinations were found to be 0.4 M NaSCN together with 10.0% DMSO, and 1.0 M MgCl2 with 15.0% DMSO. At this optimum combination, quality controls spiked with mAb at 50.0 ng/ml in eighteen individual human sera and plasmas were quantified with an overall accuracy of 102.0%. All of these QCs fulfilled the acceptance criteria of 80.0-120.0% accuracy and precision below 20.0%. The assay was also successfully applied to the quantification of two other mAbs in human serum. Furthermore, the use of the assay was extended to pre-clinical species (cynomolgus monkey and rat serum). Here, the performed validation experiments confirmed the utility of the assay and demonstrated that the assay allowed quantification of mAb from 50.0 ng/ml to 100.0 microg/ml in cynomolgus monkey serum. The method has then been applied to a pharmacokinetic study in cynomolgus monkeys. In summary, this work demonstrates the efficacy of the combination of a chaotropic salt with DMSO to minimize matrix interferences in an ELISA. The robustness thus obtained allowed the successful establishment of a cost effective, target-based ELISA format for use in pharmacokinetic studies, that is easily applicable for the quantification of mAbs in various matrices such as human, cynomolgus monkey or rat serum and plasma.

A role for membrane IgD in the tolerance of pathological human rheumatoid factor B cells.

Under non-autoimmune conditions, rheumatoid factor (RF) B cells coexist peacefully with their antigen (IgG), or can be transiently activated during secondary immune responses because they can present xenoantigens to specific T cells captured in immune complex form. Such a situation should lead to affinity maturation of RF B cells and potentially dangerous production of high-affinity RF. We used two lines of transgenic mice expressing a somatically mutated pathological human RF in presence (IgM and IgD) or in absence (IgM only) of surface IgD, and confirm that RF B cell tolerance can result from an antigen-induced specific, but incomplete, deletion of naive RF B cells after antigen encounter. This deletion mainly concerns immature, transitional B cells. On the contrary, mature, IgM- and IgD-expressing RF B cells are resistant to such a deletion. These IgM and IgD RF B cells are functional and activable through both B cell receptor dependent (anti-IgM) and independent (LPS) pathways, but they are not fully responsive to human IgG either in vivo or in vitro. Taken together, these results suggest that another mechanism could be involved in the silencing of mature naive IgM and IgD RF B cells.