Pathway Different Activators (PADIAC)
Research Area: Cellular Biology
Expedition(s): 25 and 26
Principal Investigator(s): ● Isabelle Walther, PhD, Swiss Federal Institute of Technology,
Space Biology, Zurich, Switzerland
RESEARCH OBJECTIVES
The Pathway Different Activators (PADIAC) experiment
will test the hypothesis that the inhibition of interleukin- 2
(IL-2) receptor expression on T cells (mature white blood
cells from the thymus) in microgravity is due to a
sensitivity of the CD28 (molecule required for T-Cell
stimulation) co-stimulatory pathway to microgravity and
determine how microgravity affects the expression of
genes mediated by CD28 activation.
RESULTS
The quality of data for the 4-hour samples was excellent,
though a few more ground studies are needed on the
4-hour samples to determine signal transduction under the 3 methods of activation to
complete the picture. The data for the 24 -hour samples was less striking most likely due to the
fact that the RNA from the 24-hour samples was in low amount.
The data are excellent for the 4-hour data with changes seen in IL2Rα, Xcl2, EGR-1, GMCSF and
IFNγ for each activation. In most cases, the ConA/CD28 and the more physiological CD3/CD28
activations were comparable, confirming that all previous work with ConA/CD28 is reliable. We
had thought by bypassing the IL-2 step would eliminate the suppression of spaceflight, but that
was not the case. The effectiveness of the 3 activations demonstrated that all 3 stimulations
were effective suggesting that IL2 is not the only limiting factor in microgravity. These
experiments help to understand immune system activation by introducing the variable of
gravity. As in mathematics, the elimination of a variable many times can eventually solve the
equation. Spaceflight causes changes in the ability of the T cells to respond to a simulated
infection. The central hypothesis was that this effect was solely dependent on IL-2, however,
this experiment showed that IL-2 was not the only factor.
This investigation is complete; however additional results are pending publication.
Pathway Different Activators hardware. ESA
image.