Systems Biomechanics of the Cell - Systems Biomechanics of the Cell - page 50

Fig. 28 Oscillations of the lymphocyte centrosome between two immunological synapses.
( a ) Model cell structure. ( b ) Trajectories of the centrosome predicted for the indicated angles
between the synaptic planes. Dashed curve is an experimental trajectory. Reproduced from Kim
and Maly ( 2009 ) under the Creative Commons Attribution License
duration of the movement phase could be reproduced (Fig. 28b ). Whereas the match
of the absolute model time scale to the experiment is data fitting and therefore not
particularly significant, the fact that the computed phase of pause and the computed
phase of migration can have the same relative duration as seen in the experiment is
remarkable. It indicates that the simple deterministic mechanics may indeed account
for the complex motility of the confined cell body in the conjugated T lymphocytes.
In the light of the Kim-Maly model, the pause of the centrosome and the associ-
ated secretory apparatus of the lymphocyte's cell body next to each of the synaptic
areas of the cell boundary appears to arise from the delayed relaxation of microtu-
bules that were trailing during the last period of cell body migration. This can be
discerned by examining Fig. 28 closely, and it is the same factor that leads, in the
extreme, to the irreversible, ratchet-like behavior of the model following very large
reorientations (Fig. 24 ). In comparison, the medium-range migration between the
two synapses can be reversible. Compared, on the other hand, with the relatively
small-amplitude oscillations within a synapse (Fig. 25 ), the migration of the centro-
some between the synapses winds the trailing microtubules around the nucleus
more. It takes them longer to relax and contact the other synaptic area after the