Effects of nucleus on leukocyte recovery

The rheological properties of a leukocyte significantly affect its biologic al and mechanical characteristics. To date, existing physical models of leu kocyte are not capable of quantitatively explaining the wide range of defor mation and recovery behaviors observed in experiment. However, a compound d rop model has gained some success. In the present work, we investigate the effect of nucleus size and position, and the relative rheological propertie s of cytoplasm and nucleus, on cell recovery dynamics. Two nucleus sizes co rresponding to that of neutrophil and lymphocyte are considered. Direct com parison between numerical simulations and experimental observation is made. Results indicate that the time scale ratio between the nucleus and cytopla sm plays an important role in cell recovery characteristics. Comparable tim e scales between the two cell components yield favorable agreement in recov ery rates between numerical and experimental observations; disparate time s cales, on the other hand, result in recovery behavior and cell shapes incon sistent with experiments. Furthermore, it is found that the nucleus eccentr icity 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 leukocyt es. (C) 1999 Biomedical Engineering Society. [S0090-6964(99)00105-8].