Columbia University Medical Center (CUMC) researchers analysed tissues harvested from organ donors, all of whom had died suddenly of traumatic causes, ranging in age from 15 to 60.
Samples were taken from tissues that have direct contact with pathogens, including lymph, lung, spleen, and small and large intestines. All donors were HIV-negative and free of cancer and other chronic or immunological diseases.
T cells, a type of white blood cell, play a major role in cell-mediated immunity, in which the immune system produces various types of cells to defend the body against pathogens, cancer cells, and foreign substances.
"We found that T cells are highly compartmentalised - that is, each tissue we examined had its own complement of T cells," said study leader Donna L Farber, professor of surgical sciences at CUMC.
"The results were remarkably similar in all donors, even though these people were very different in terms of age, background, and lifestyle," Farber said in a statement.
The researchers also discovered a receptor that is expressed on the surface of "tissue-resident" T cells but not on circulating T cells.
Using this marker, Farber and her colleagues established that the blood is its own compartment.
"In other words, T cells found in circulation are not the same as T cells in the tissues," said Farber.
According to the researchers, the findings establish a baseline for T-cell immunity in healthy individuals. This knowledge can be used to better understand how various tissues respond to site-specific and systemic autoimmune and inflammatory diseases.
The findings can therefore powerfully inform the development of new vaccine strategies.
"To make better vaccines, it may be necessary to activate a T-cell response at the site of an infection, not just in the general circulation," said Farber.
"But first we have to know what types of immune cells are in those tissues and how they function. This is a first step in that direction," Farber added.
The study was published in the journal Immunity.
