To Understand Immune System Failures

UMDNJ University Professor Yufang Shi, DVM, PhD, is a Robert Wood Johnson Medical School professor of molecular genetics, microbiology, and immunology. His research is funded by the National Institutes of Health as well as the NSBRI, a consortium of leading biomedical institutions.

When astronauts return from space flight, they experience significantly increased rates of infection. Yufang Shi knows why. In breakthrough research being conducted for the National Space Biomedical Research Institute (NSBRI), Shi has demonstrated that when your feet aren't on the ground, lymphocytes in your bloodstream send out suicide signals in the form of Fas proteins and immunity "is significantly altered." You are more likely to get sick. This is a cellular suicidal path, known as apoptosis, that only becomes worse when these Fas proteins meet and bind with molecules known as Fas ligands (FasL).

To unravel this biochemical metabolic conundrum, Shi has been using what is known as "a hindlimb unloading  (HU) protocol" to simulate the effects on a body of weightlessness in outer space. However, the repercussions of his research are just as significant for bedridden confinement or paralysis here on earth. "These unnatural positions cause psychogenic stress as well as a shift of fluid to the head and lack of weight-bearing on the rear legs." After only two days of being off their hind legs, Shi's animal models suffered a 50 percent decrease in the T-cells which originate in the bone marrow, mature in the thymus, and fight off infections. Shi explains, "Stress induced lymphopenia has been observed in surgical patients, over-exercised athletes, persons under various psychological stresses and animals subjected to restraint." However, until now, the exact mechanisms were little understood. Shi has shown that the stress caused by being off your feet can, in fact, induce apoptosis in your T-cells.