Studies on chemoattractant-induced polarisation and locomotion of human blood leucocytes

Migration of leucocytes into sites of into lamination and to phagocytose damaged cells and invading microorganisms is an immunological reaction of paramount importance. The circulating blood monocytes together with tissue macrophages and blood neutrophils are the cells which carry out this phagocytic function. Studies on different aspects of the locomotion of human blood monocytes are presented in this thesis. The neutrophils and the non-adherent mononuclear cells from human peripheral blood were also used in some experiments. Studies on monocytes were greatly hampered in the past because of the difficulties in obtaining purified preparations of the cells, Several procedures were tried in the present study, most of which for one reason or another, were unsatisfactory. The BHK microexudate method produced a considerably higher yield of purified populations of monocytes in suspension and was ultimately selected for subsequent studies. The responses of human blood monocytes to chemotactic factors were studied using an assay of morphological polarisation. Changes in cell morphology from a spherical to a polarised configuration which occurred within a few minutes of adding a chemotactic factor, were scored after incubating the cells in suspension followed by fixation with glutaraldehyde. Polarisation is the initial event in locomotion and can be scored accurately as has been shown in neutrophils. In contrast to neutrophils where more than 90% cells in a population can respond towards the formylated peptide FMLP, only 60 or so percent of the blood monocytes can do so. The rest of the cells do not bear receptors for FMLP and hence can not respond. Monocytes showed distinct morphological shapes in different concentrations of FMLP. The cells were most polarised in 5 X 10-