Physical and Chemical Determinants of Leucocyte Locomotion

Abstract

It is now generally accepted that chemotaxis is an important determinant of leucocyte accumulation in sites of inflammation. A wide range of chemotactic factors has been identified and, more recently, progress has been made in understanding how they bind to the surface of the leucocyte and how they evoke a directional locomotor response. Nearly all of this information has been obtained using neutrophils, since these are the easiest of the leucocytes to work with. Cells of the mononuclear phagocyte system certainly also show chemotaxis, but we are much further from understanding their response in detail. Mononuclear phagocytes, whether as blood monocytes or as exudate macrophages, are more difficult to purify than neutrophils and, although methods have improved of late, even the most purified populations contain lymphocytes and cells of uncertain identity. Probably more of a problem is the fact that mononuclear phagocytes are capable of considerable differentiation and, as yet, we know very little of the effect of differentiation on their locomotor capacity, or about the effect of macrophage heterogeneity on chemotaxis. This subject is discussed by Dr. Leonard in this volume.