Virus-induced order-disorder transition of moving human leukocytes

Abstract

In vitro analysis of human granulocytes migrating on a glass surface exhibits three different kinds of movement: i) locomotion: it is characterized by changes in cell shape, but practically no movement of the centre of mass; ii) chemokinesis: an isotropic distribution of chemotactic molecules (FMLP=N-formylmethionylleucylphenylalanine) induces a random walk which is described by the track velocity of the centre of mass and the diffusion constant; iii) chemotaxis: in the case of an anisotropic distribution of FMLP a directed cell movement occurs which is described by the track velocity and drift velocity. The directed cell movement can also be characterized by the anisotropic-angular-distribution function of the elongated cells. The polar-order parameterP 1 (=degree of orientation) as well as the track velocity characterize also the chemotaxis. The chemokinesis and chemotaxis of a moving cell are described by an equation which has the structure of the Langevin equation. However, the collision time has to be replaced by a characteristic time which is determined by an internal program of the cell. Interaction of Echo 9 virus with granulocytes resulted in a disturbed chemotactic cellular response in which the track velocity was practically unaffected, but the degree of orientation exhibited a virus dose and time dependence. At a fixed virus dose, the degree of orientation decayed with time according to an exponential law. The inverse of the corresponding characteristic time constant depended on the virus dose after a logarithmic law. There existed a threshold viral dose at 0.8 infective viral dose (p.f.u.). For viral doses below this value chemotaxis was not affected. However, for viral doses above this value chemotaxis was disturbed where the degree of orientation approached zero (chemotaxis→chemokinesis) indicating an order-disorder transition. The angular-distribution function indicated that the virus-treated cells consisted of two types of cell population: one exhibited an unchanged degree of orientation (P 1=0.8), whereas the other cells were not directed (P 1=0). The order-disorder transition is discussed by a phenomenological-potential model and by a chemical-reaction model. Furthermore, the disturbed chemotaxis is discussed in the context of a coherence length of the moving cell. Ourin vitro results were correlated to clinical and pathological anatomical findings in viral-induced human diseases.