CD45 PHOSPHATASE IN JURKAT CELLS IS NECESSARY FOR RESPONSE TO APPLIEDELF MAGNETIC-FIELDS

Oscillations of free intracellular calcium [Ca2+](i) were seen in indi vidual Jurkat cells as response to a 50 Hz, 0.15 mT magnetic field (MF ). In contrast, a CD45-deficient Jurkat cell line was unable to respon d to MF stimulation, The phosphatase activity of CD45 has been implica ted to regulate p56(lck) tyrosine kinase activity by removing an inhib itory phosphate, By using Jurkat cells that expressed a chimeric molec ule, comprising the cytoplasmic phosphatase domain of CD45, the MF ind uced calcium response was restored, This showed the necessity for an i ntact signal transduction pathway leading to a calcium increase as a r esult of stimulation of cells by MF. Thus, our data suggest that the t arget for the applied MF are molecules involved in early events in the signalling pathway from the T cell antigen receptor.