News ID: 123520
Published: 0322 GMT July 29, 2015

Immune cells in skin remember, defend against parasites

Immune cells in skin remember, defend against parasites

Just as the brain forms memories of familiar faces, the immune system remembers pathogens it has encountered in the past. T cells with these memories circulate in the blood stream looking for sites of new infection.

Recently, however, researchers have shown that memory T cells specific to viral infections can also set up residence in particular tissues. There, they stand guard, ready to respond quickly to the first sign of reinfection.

Now, research led by a team from the University Of Pennsylvania School Of Veterinary Medicine shows that these resident memory T cells also form in response to parasite infection. The new study found that, after infection with the parasitic disease leishmaniasis, a population of T cells with a memory for the parasite remained in the skin, Science Daily wrote.

This is the first time that a group of T cells has been found to be resident in a tissue in response to a parasite infection, and the finding could help inform efforts to develop an effective vaccine for leishmaniasis, as well as other diseases such as tuberculosis and leprosy.

T cells detect invaders in the body and can kill infected cells either directly, in the case of CD8 T cells, or indirectly, in the case of CD4 T cells, by enlisting the help of other immune cells. Scott's lab has found that CD4 cells are particularly important in controlling leishmaniasis.

After an infection, a population of memory T cells remains in the body to respond quickly if reinfection occurs. Yet findings from Scott's lab supported the idea that circulating T cells weren't the only way the immune system protected against reinfection.

Studies in the lab showed that transferring circulating CD4 T cells from a mouse that had contracted and then recovered from leishmania infection into a mouse that had never had the infection offered partial but not complete protection from subsequent infection.

Taking mice that had and then recovered from leishmaniasis, Scott's team looked for Leishmania parasite-specific T cells in areas of the skin, both from the site of infection and other sites. They found Leishmania-responsive cells throughout the skin of these mice, even in sites distant from the initial infection, as long as a year after infection.

"It was a little surprising that there were so many Leishmania-reacting cells in the skin," Scott said, "But it still left us with, well, maybe they're just circulating cells that happen to have been found in the skin."

Resource: Science Daily
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