The effects of gliadin and glyc-gli on leukocyte chemiluminescence response, cytotoxic activity and locomotion were assessed in vitro. A dose-dependent increase in chemiluminescence response of neutrophils stimulated by Zymosan was observed by using gliadin at concentrations ranging between 1 and 20 micrograms. By increasing glyc-gli concentrations, a bimodal response was observed with an enhancement up to 50 micrograms/ml, followed by dose-dependent suppressive effects. The cytotoxic activity of a suspension of peripheral blood mononuclear cells on the human myeloid line K562 was assessed in a Chromium release assay. By pretreating effector cells with optimal doses of gliadin (5 micrograms/ml) or glyc-gli (50 micrograms/ml), an enhancement of cytotoxic activity, similar to that of the gamma-Interferon, could be achieved. Finally glyc-gli was found to elicit neutrophil chemokinesis. The possible implications of these findings in diseases characterized by gluten intolerance are discussed.