The data on the content of soluble and membrane forms of CD23 antigen in healthy subjects are presented. Three groups were distinguished: the first group with low contents of both free and membrane CD23; the second group with increased contents of both forms; and the third group with an increased content of CD23 and a significantly decreased sCD23 concentration. The conclusion has been drawn that proteolytic shedding of CD23 was carried out by activated cells against a background of an increase in the CD23+ phenotype frequency in lymphocytes. An increase in the expression of CD23+ by lymphocytes was associated with an increase in the concentration of IL-6 and IFN-γ cytokines and the natural mitogen α-fetoprotein. Shedding of CD23 by cells and an increase in sCD23 occurred upon an excessive increase in IgE and antiinflammatory cytokine IL-10. The ratio between the membrane and free forms of CD23 was determined by the activity of the expression and shedding and level of an associate formation.