Galvanotaxis of human granulocytes: electric field jump studies

The static and dynamic responses of human granulocytes to an electric field were investigated. The trajectories of the cells were determined from digitized pictures (phase contrast). The basic results are: (i) The track velocity is a constant as shown by means of the velocity autocorrelation function. (ii) The chemokinetic signal transduction/response mechanism is described in analogy to enzyme kinetics. The model predicts a single gaussian for the track velocity distribution density as measured. (iii) The mean drift velocity induced by an electric field, is the product of the mean track velocity and the polar order parameter. (iv) The galvanotactic dose-response curve was determined and described by using a generating function. This function is linear in E for E less than EO = 0.78 V/mm with a galvanotaxis coefficient KG of (-0.22 V/mm)-1 at 2.5 mM Ca++. For E greater than EO the galvanotactic response is diminished. This inhibition is described by a second term in the generating function (-KG.KI(E-EO)) with an inhibition coefficient KI of 3.5 (v) The characteristic time involved in directed movement is a function of the applied electric field strength: about 30 s at low field strengths and below 10 s at high field strengths. The characteristic time is 32.4 s if the cells have to make a large change in direction of movement even at large field strength (E-jump). (vi) The lag-time between signal recognition and cellular response was 8.3 s. (vii) The galvanotactic response is Ca++ dependent. The granulocytes move towards the anode at 2.5 mM Ca++ towards the cathode at 0.1 mM Ca++. (viii) The directed movement of granulocytes can be described by a proportional-integral controller.