Microgravity suppresses 99 key immune genes

Researchers at the San Francisco VA Medical Center have identified a
set of key immune-response genes that do not turn on in a weightless
environment. The discovery is another clue in the effort to solve an
almost 40-year-old mystery: why the human immune system does not
function well in the weightlessness of space.

The researchers, led by SFVAMC biochemist and former astronaut Millie
Hughes-Fulford, PhD, identified a signaling pathway called PKA that in
a gravity field responds to the presence of a pathogen by stimulating
the expression of 99 genes that in turn cause the activation of
T-cells, which are essential for proper immune function.

Hughes-Fulford found that in the simulated absence of gravity, the PKA
pathway did not respond to the pathogen's presence; as a result, 91
genes were not induced and eight genes were significantly inhibited,
severely reducing the activation of T-cells. The paper was published
on October 6 in FJ Express, the online rapid-publication section of
the Journal of the Federation of American Societies for Experimental
Biology.

"This is a specific signal pathway that is not working in the absence
of gravity," says Hughes-Fulford, who is also an adjunct professor of
medicine at the University of California, San Francisco. "You're
short-circuiting a whole lot of the immune response -- namely, the
ability to proliferate T-cells -- which shouldn't be a surprise,
because life evolved in Earth's gravity field."

Hughes-Fulford points out that there are only two known situations in
which T-cell function is so severely compromised: HIV infection and
weightlessness.

The research was conducted on human immune cells in culture that were
placed in a device called a random positioning machine, which
simulates freefall.

The researchers found that three other pathways which regulate immune
function -- P13K, PKC, and pLAT -- were not affected by the absence of
gravity.

"Why do some pathways work and some not? Perhaps it's differences in
the cytoskeleton the interior architecture of the cell," speculates
Hughes-Fulford. "It's the infrastructure of the cell, a membrane made
of lipid, and maybe without gravity it's not as well-organized as it
should be."

Article continues at:
http://www.scienceblog.com/cms/microgravity_suppresses_99_key_immune_genes_9069

TangoMan