Rheology of rat basophilic leukemia cells

Rat basophilic leukemia (RBL) cells, decorated with IgE, have been shown to bind irreversibly to antigen-coated substrates. In this paper we measured RBL cell deformability and demonstrated that this irreversible binding is not due to a compliant cellular rheology of these cells. The rheological properties of RBL cells were assessed with single-cell micropipette aspiration. Small-sized (G1/G0 phase) cells were found to be more deformable than medium-sized (S phase) cells. No changes in cellular rheology were observed after binding of anti-dinitrophenol IgE to Fce receptors. Furthermore, cytoplasmic viscosity mu showed power-law dependence on mean shear rate gama m: mu = mu c(gamma m/gamma c)-b, where mu c is a characteristic viscosity at characteristic shear rate gamma c, and b is a material coefficient. All the cells exhibited similar dependence on shear rate (b approximately 0.5). When gamma c was set to 1 s-1. mu c = 480 +/- 10,560 +/- 40 and 490 +/- 10 Pa.s for G1/G0, S cells, and G1/G0 cells treated with the antibody, respectively. In general. RBL cells were much more rigid than normal neutrophils (mu c = 130 +/- 20 Pa, s b = 0.5). Thus the biochemistry of the adhesion molecules, not the cellular deformability of the cell, is the cause of the irreversibility of RBL cell adhesion under flow.