New findings in immune cells could improve vaccine design

Little is still known about the immune system's ability to remember disease-causing bacteria that have been defeated and avoid repeated infections, but a new study published in the journal Science Immunology clarifies an important aspect of
the problem.

Researchers at Rutgers University used specially bred mice to distinguish the effects of two immune cells, called tissue-resident memory T cells (Trm cells), that protect against infection and cancer
.
Their work may help improve the efficacy of vaccines and fight a variety of autoimmune diseases
.

Tessa Bergsbaken, assistant professor at Rutgers College of New Jersey Medical College and senior author of the study, said: "Understanding the function of each Trm cell type allows us to formulate vaccines that produce the most effective type of Trm cells to fight specific infections, and our previous work shows that we can modify the vaccine to alter the balance
of these two cell types.
" Trm cells are not always beneficial
.
Certain autoimmune diseases can be driven by Trm cells, and we think what we know will also help us discover how these cells work against us
.
”

Each new infection prompts the immune system to produce customized T cells (a type of white blood cell) to protect itself
.
After the fight is over, the immune system continues to produce the same T cells (albeit in much smaller numbers) in case the invaders come back
.

Many T cells circulate throughout the body, "looking for" the antigens they are supposed to protect, but Trm cells attach to isolated tissues, isolating the body from the outside world: the skin, eyes, nasal passages, and entire digestive tract
.
Previous studies have revealed various subtypes of Trm cells, distinguished primarily by the expression of two specific proteins, CD103 and CD69
.
However, the functional differences between TRM subtypes remain a mystery
.

In this study, the researchers engineered mice to enable them to label CD103+ Trm cells, which are produced
in response to a common bacterial infection, Yersinia pseudotuberculosis.
This, in turn, allowed them to distinguish the response of CD103+ cells to reinfection from the response of CD103-Trm cells
.

They found that CD103+ cells do not multiply after reinfection and do not attack invaders
directly.
Instead, it is CD103 cells that multiply and attack the bacteria
when they are reinfected.

Bergsbaken said: "What we see is essentially a division of labor between these two different cells, but CD103-Trm cells play a more important role
.
Producing a higher number of CD103-Trm cells during initial infection or vaccination may be better protected against subsequent infections
.
”

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