ANTI-CD38 PREVENTS THE DEVELOPMENT OF THE ADAPTIVE RESPONSE INDUCED BY X-RAYS IN HUMAN-LYMPHOCYTES

Irradiation of human lymphocytes (1 cGy X-rays, 37 degrees C) evoked a n similar to 30% decrease in the frequency of micronuclei upon subsequ ent X-irradiation (1.5 Gy), The response was reflected in a lower micr onucleus frequency but not in the DNA repair rate measured by the come t assay directly after the challenge dose. Treatment of lymphocytes wi th anti-CD38 antibody 1 h before irradiation with the adaptive dose pr evented the development of the adaptive response measured as micronucl ei frequency, but adaptation was not reflected in a lower rate of DNA repair, measured by the alkaline version of the 'comet' assay. In lymp hocytes that were anti-CD38-treated and irradiated and or irradiated w ith the adaptive dose the rate of DNA repair was not changed. However, the mean DNA damage level in adapted anti-CD38-treated lymphocytes wa s significantly lower than that in the control lymphocytes at all time points, We conclude that ligation of CD38 by antibody initiates signa lling that prevents the development of the adaptive response induced b y X-rays, Lower chromosome damage revealed by the cytokinesis block-mi cronucleus test in the adapted lymphocytes is unrelated to DNA repair rate.