Adhesion and spreading behaviour of human peripheral blood mononuclear cells (PBMC) in vitro

While the in vitro adhesion and spreading behaviour of fibroblastic cells have been extensively documented, similar studies on the cells of immunological importance are still lacking. We report here the in vitro adhesion and spreading behaviour of normal human peripheral blood mononuclear cells (PBMC) isolated by the Ficoll-Hypaque technique. Since the presence of serum retarded cell adhesion by 25%, serum-free RPMI-1640 medium was used in these studies. Based on the light and scanning electron microscope studies, glass-immobilized PBMC were classified on the basis of their spreading behaviour as follows: (A) Cells with non-deformable nucleus: I, Cytoplasm non-spread; II, Cytoplasm partially spread; III, Cytoplasm well spread. (B) Cells with deformable nucleus: IV, Nucleus partially spread; cytoplasm well spread; V, Nucleus and cytoplasm well spread. These different cell types occur in the normal human peripheral blood in the relative frequency of 24 ± 3: 27 ± 4: 13 ± 2: 20 ± 5: 16 ± 2 percent. Cell types I–III show the characteristics of lymphocytes and the cells of type V were identified as monocytes, while the nature of cell type IV is not known at present. The immobilized PBMC contained T and B cells as confirmed by sheep erythrocyte (SE) and mouse erythrocyte (ME) rosette formation and surface immunoglobulin. The spreading behaviour of these cells appears to be limited by factors such as available surface membrane area, number and density of adhesion sites, other membrane receptors and the deformability of cell and nuclear membranes. Further characterization of these cell types would aid as a behavioural marker for the subpopulations of lymphocytes and monocytes in health and disease.