Functional recovery of peripheral blood mononuclear cells in modeled microgravity

Immune function is suppressed in space flight, demonstrated by reduced mitogen-stimulated proliferation of postflight astronaut peripheral blood mononuclear cells (PBMCs). While flight studies are limited, the development of rotating wall vessel (RWV) bioreactors, such as the high aspect ratio vessel (HARV), has facilitated ground-based studies of the effects of modeled microgravity (MMG) on cell-mediated immunity. Astronauts regain immune function 3 days postflight, but this recovery has not yet been demonstrated following MMG. MMG eliminated phytohemagglutinin (PHA)-stimulated proliferation of PBMCs. Upon removal from HARV, full recovery was gradually achieved over a 72 h period, in agreement with postflight studies of astronauts. Recovery from MMG delayed, but did not reduce, the maximal proliferative response compared with PHA-activated stationary cultures. Likewise, peak expression of T cell surface activation markers CD69 and CD25 was delayed upon stimulation following exposure to MMG. MMG and recovery from MMG differentially affected the detection of IL-2 and IFN in supernatants. Further development of this model of immune recovery is important for investigating the mechanisms of immune suppression and recovery in space flight, as well as possible countermeasures to prevent immunosuppression or enhance recovery. Given the analogous immune suppression observed in microgravity, MMG, and aging, further investigation may also lead to advances in anti-aging medicine.