Defensins are a family of antimicrobial cationic peptides localized mainly in neutrophile granulocytes. The defensins are known to display corticostatic activity by means of suppression of stress- and ACTH-induced rise in corticosterone level in the blood. The present study examines influence of defensin fractions with different corticostatic activity on suppressor functions of T-lymphocytes. It was shown that corticostatic effects of defensins are revealed under an increased level of glucocorticoids in the blood after hydrocortisone application. Defensins were found to limit the inhibitory action of glucocorticoids on the suppressor functions of T-lymphocytes. After adrenalectomy this phenomenon was not observed.