A Change in Posture Significantly Affects Plasma Concentrations of Large Molecules Such as IgG Antibodies.

In several studies with monoclonal antibodies, we observed spikes in plasma concentration profiles coinciding with a change of posture of study subjects. We hypothesized that these unexpected changes were due to fluid shifts from plasma to the interstitium. The objective of this study was to investigate size and time course of the change in total immunoglobulin G (IgG) concentration after a change in posture.