Technicium as a radiolabel in the assessment of in vivo human Fc clearance.

99m-Tc was used as a radiolabel to study in vivo human clearance of IgG sensitized erythrocytes. Stannous chloride pretreatment at different doses and varying amounts of 99m-Tc were studied with respect to radiolabelling efficiency and elution. Mean in vivo clearance rates in systemic lupus erythematosus patients were significantly prolonged compared to controls. Using as little as 200 microCi of 99m-Tc per patient, in vivo human immune clearance can be determined with a minimal radiation biohazard. With this method, serial immune determinations can be performed within very short time frames, allowing for monitoring effects of immunomodulatory therapy as well as variations in disease activity.