A novel downstream process is reported for preparative scale prodn. of dimeric IgA, a protein with potential pharmaceutical applications. Time-consuming size exclusion chromatog. was replaced by ceramic hydroxyapatite chromatog. (CHT). A clear baseline sepn. of the dimeric IgA from the polymeric forms using a step-gradient-step protein elution program is described. Application of this method for IgA anal. during prodn. is suggested. [on SciFinder (R)]