The objectives of this experiment are to confirm two hypotheses in real 0g: firstly, that the genetic expression of IL-2 and of its receptor is altered together with the expression or activation of other components of the signal transduction pathways; and secondly, that there may be a threshold of sensitivity between 0 and 0.5g. Below 0.5g T cell function is inhibited, whereas between 0.5 and 1g it is nearly normal, i.e. as it is at 1g.

The experiment LEUKIN consists of two components: In the LEU-M experiment, using previously flown hardware MIA, T-cells will be activated and after a short incubation fixed by addition of formaldehyde. In the LEU-L experiment, using previously flown LYCIS hardware, T-cells will be activated and after 4h lysed with RNA later solution.

The T cells were purified from fresh human blood (or buffy coat) shortly before launch and sealed in two types of culture containers. One type (called LYCIS) is designed to, first, activate the T cells and, second, to lyse the cells in order to isolate RNA and determine genetic expression. The other type of container (called MIA) is designed to, first, activate the T cells and, second, to fix the cells in order to determine the activation of proteins involved in the signal transduction pathways.

The experiment LEUKIN is subdivided in two parts:

LEU-L (derived from LYCIS)

In orbit the cultures are activated after a pre-incubation time of 2-4h at 36.5°C, they are incubated for 4 hours at 0g, 0.5g, 1g respectively. Then the cells are lysed and stored refrigerated between 4 and 6°C until hand-over to the investigators.  The transfer to ambient temperature can be performed up to 30h before dedocking.

At delivery each experiment unit contains T cells and medium. Two dispensers and one plastic container with activator and fixative barrels are located separately.

The experiment begins as soon as possible after docking. The reason for this is that the cells are isolated from blood already 1.5d before launch and that they are surviving not more than 6d. Already 5 days after isolation the survival rate is reduced. Therefore the beginning of the experiment should be as soon as possible.

LEU-M (derived from MIA)

In orbit the cultures are activated after a pre-incubation time of 2-4h at 36.5°C , then incubated for 30 min at 0 g, 0.5g, 1 g respectively. Then the cells are fixed and stored at 4 to 6°C, until transfer to ambient stowage for descent. After landing the samples are stored at 4 to 6°C until delivery to PI. For the LEU-M storage it is important that the time at ambient is as short as possible. Max 24h before dedocking.

At delivery each experiment unit contains T cells, culture medium, activator and paraformaldehyde as a fixative in their respective compartments. Each LEU-M unit has a number engraved on the cover plate. The experiment should begin as soon as possible after docking. The reason for this is that the cells are isolated from blood already 1.5d before launch and that they are surviving not more than 6d. Already 5 days after isolation the survival rate is reduced. Therefore the beginning of the experiment should be as soon as possible. 

The cells that experienced simulated gravity as if on Earth were found to be in good health compared to their weightless equivalents.

By comparing the samples, investigators saw what was stopping the immune cells from working properly. A specific transmitter in the immune cells, called the Rel/NF-κB pathway, stops working in weightlessness.