Immune T-cell activation

Who it is for

• University and hospital immunology labs studying T-cell signalling and immunosenescence (ageing of the immune system)
• Space agency human-research programmes that need data on astronaut immune dysregulation and on countermeasures
• Pharmaceutical and biotech groups testing immunomodulating compounds on a model where T-cell activation is already impaired
• Research groups that already have ISS T-cell data and want a repeat flight with a different activator, donor set or time points

What earlier flights found

How LELP-1 runs it

Sample. Human peripheral T cells (or PBMC, which keep the accessory cells) from 2 donors. Cells are cryopreserved before launch. They can be pre-labelled with a cell-tracking dye so proliferation can be measured after return. Container. Large bay 24-well cassette with gas-permeable lids and a filtered (about 0.4 um) outlet on each well, so supernatant can be drawn off without removing cells. Planned layout: 2 donors x 3 conditions (unstimulated; Con A + anti-CD28 to match the ISS heritage; soluble anti-CD3/anti-CD28) x 3 time points = 18 wells, plus 6 wells for imaging, viability and spares. Launch. cryopreserved (-80 C passive cassette); medium, activators and fixatives held in bay reservoirs. Light and gas. No light needed (dark incubation; the microscope LEDs run only during imaging). No CO2 supply: HEPES-buffered RPMI-type medium in sealed wells with gas-permeable lids.

1. day -1

   Load the cryo cassette, reagent reservoirs (HEPES medium, Con A + anti-CD28, anti-CD3/anti-CD28, RNAlater, paraformaldehyde fixative) and the empty well cassette. Fix a pre-launch baseline aliquot of each donor on the ground.

2. day 0

   Launch. Cells stay in the passive -80 C cassette. Bay reservoirs are held at 4 C.

3. day 1

   Automated thaw at 37 C, then about 1:10 dilution into warm medium to lower the DMSO level, and dispensing into the wells. Brightfield images give the starting cell count and morphology.

4. day 2

   After an 18-24 h rest at 37 C, fix one unstimulated set (t = 0) in RNAlater. Pump the activators into the stimulated wells. Lock out arm motion for the first 2 h. At 1.5 h, add RNAlater to the early-gene wells, as in the 2006 ISS flight.

5. day 3

   24 h after activation: draw supernatant through the well filter into a sealed sample reservoir for cytokine analysis, then fix the cells with paraformaldehyde for flow cytometry (CD69, CD25). Take brightfield images of cell clustering every 6 h from day 2.

6. day 5

   72 h after activation: split the final wells between paraformaldehyde (proliferation, Ki-67 or dye dilution) and RNAlater. Image all wells. Set the bay to 4 C.

7. day 7

   Bay held at 4 C through re-entry and splashdown. Fixed cassette and supernatant reservoir are handed to the customer's courier at 4 C.

The payload module, in CAD

Every item in the module sheet, drawn and packed into the large bay deck by deck. The back face mates with the bay: blind-mate connector, and a cold wall against the bay's thermoelectric block. The front face carries Dexter-L's grapple fixture, and the fluid lines run down a channel just behind it. What you load before launch is marked blue in the configurator's payload guide.

CAD generated by cad/build_modules.py (CadQuery, OpenCascade kernel) from the catalog's module items: concept geometry, not a released design. Standard parts keep their real formats; the rest are sized from their catalog mass. The front panel and grapple fixture are left off in the 3-D view and are in the STEP.

• The XY stage travels 96.5 x 57.9 mm, so every one of the 24 wells reaches the objective; with the stage the imaging stack is 232 x 151 mm, which sets the module's depth budget. The catalog lists no stage for this microscope: it is drawn inside the microscope's mass.
• Reagent volumes the catalog does not state are split evenly from 75 % of the reservoir item's mass.
• Fluid pack: 6 reagent bags in 2 layers (214 x 103 x 46 mm), every port on a front edge.
• The supernatant reservoir lies under the reagent bags and fills the room they free: they hold 750 mL, it needs 150 mL.
• The catalog gives 0.36 kg for structure and containment; as an aluminium box that is a 0.17 mm skin on 0.11 kg of posts and shelves. Thin: the bay rails have to carry the launch loads, or the module needs more structure mass.
• The grapple fixture stands 26 mm proud of the front panel, into the bay opening; everything else is inside the bay envelope.

Ground control

Synchronous ground control: an identical flight-model bay and cassette loaded with the same donor cell lots and reagent batches. It replays the same timeline (offset by a few hours) and the recorded flight temperature profile, including the -80 C hold, thaw, 37 C phases and the 4 C return hold. If possible, it also gets a launch vibration profile on a shaker table. Add a pre-launch baseline fixed on the ground. The key flight control in the 2006 and 2014 ISS studies was an on-board 1 g centrifuge running at the same time in KUBIK, which separates microgravity from radiation, launch and handling effects. LELP-1 should fly one (see needs). Without it, the result is flight versus ground only. Because the 2006 flight launched live cells unfrozen, the cryopreserved-launch step should also be checked against fresh cells on the ground.

Coming home

All cells are chemically fixed in orbit, so nothing needs to come back alive. The manufacturer states RNAlater stabilises RNA for 1 month at 4 C (and indefinitely at -20 C), which easily covers the return. The 144 h limit is our estimate and is set by the unfrozen 24 h supernatants: drawn on day 3, they spend about 4 days in orbit, then about 20 min to courier pickup and 1-2 days in transit, so about 6 days at 4 C. The last paraformaldehyde-fixed cells (day 5) reach the lab after about 3-4 days. The bay cannot go below 4 C, so supernatants cannot be frozen in orbit; their cytokine stability for 6 days at 4 C must be checked on the ground before flight. Keep everything at 4 C in transit and avoid temperatures above 25 C.

Limits of this flight

• Without the added 1 g centrifuge, LELP-1 cannot tell microgravity effects apart from launch, radiation and handling effects. The 2006 and 2014 ISS studies used this control.
• LELP-1 has no crew and no way to pellet cells. Thawed cells are diluted rather than washed, so some DMSO stays in the medium. Medium changes must go through filters, and activator or fixative mixing relies on pumped flow because there is no sedimentation or convection.
• Bead-based activators need bead-cell contact, which in microgravity depends on mixing. The protocol therefore uses soluble activators (Con A + anti-CD28, soluble anti-CD3/CD28). Results with bead activation are not directly comparable.
• Cell attachment changes the outcome: on SLS-1, bead-attached lymphocytes and monocytes responded more in microgravity, not less. Results from suspension wells apply to suspension culture only.
• There is no CO2 supply. HEPES-buffered medium in sealed wells can drift in pH over several days of activated, high-metabolism culture, so 72 h is about the practical limit without a medium exchange.
• No in-flight flow cytometry, cytokine assay or RNA readout. In flight, the satellite only gives images and environment logs; the molecular answers come after return.
• Supernatants cannot be frozen (the bay minimum is 4 C), so cytokine values depend on about 6 days of stability at 4 C.
• A 2-14 day free-flyer studies isolated cells in vitro. It cannot reproduce astronaut immune changes in the body over months, latent virus reactivation, stress hormones or the role of other tissues.
• Few donors per flight (2 planned), so donor-to-donor variability limits the statistics. Several flights or more donors in a second bay may be needed.
• The radiation environment at 550 km sun-synchronous orbit differs from the ISS, so dose comparisons with ISS heritage data need the on-board dosimeter record.