Ability of nonviable Staphylococcus aureus Cowan I to bind ionized calcium in vitro and ex vivo in an extracorporeal perfusion system.
During immunoadsorption of plasma immunoglobulin G (IgG) and/or its complexes, using nonviable Staphylococcus aureus Cowan I (SA) as an immunoadsorbent, we observed a consistent drop in plasma calcium during every immunoadsorption procedure. The percentage of decrease in plasma calcium was directly dependent on the amount of SA adsorbent present. Although SA can bind both IgG and calcium, the degree of binding of IgG was greater than that of calcium. Calcium could not be detected in the IgG fraction of the plasma SA, however, could bind an appreciable amount of ionized calcium. Extracorporeal perfusion of plasma over SA greatly decreased plasma calcium in a hypercalcemic patient, indicating the feasibility of this method in such patients. Questions concerning the significance of lowering calcium levels as a concomitant of other effects observed in cancer patients undergoing immunoadsorption therapy using SA evolve from the above and become a new focus for attention.