Effects of nucleus on leukocyte recovery

The rheological properties of a leukocyte significantly affect its biological and mechanical characteristics. To date, existing physical models of leukocyte are not capable of quantitatively explaining the wide range of deformation and recovery behaviors observed in experiment. However, a compound drop model has gained some success. In the present work, we investigate the effect of nucleus size and position, and the relative rheological properties of cytoplasm and nucleus, on cell recovery dynamics. Two nucleus sizes corresponding to that of neutrophil and lymphocyte are considered. Direct comparison between numerical simulations and experimental observation is made. Results indicate that the time scale ratio between the nucleus and cytoplasm plays an important role in cell recovery characteristics. Comparable time scales between the two cell components yield favorable agreement in recovery rates between numerical and experimental observations; disparate time scales, on the other hand, result in recovery behavior and cell shapes inconsistent with experiments. Furthermore, it is found that the nucleus eccentricity exhibits minimum influence on all major aspects of the cell recovery characteristics. The present work offers additional evidence in support of the compound cell model for predicting the rheological behavior of leukocytes. (C) 1999 Biomedical Engineering Society. [S0090-6964(99)00105-8].