The general organization of the immune system is well known to biologists. Yet, scientists are still uncovering novel cell functions within the system. For example, David Artis, PhD, associate professor of microbiology, recently reported that a specialized type of lymphocyte, which was known to function during fetal development, also plays a critical role in protecting barrier tissues, such as skin, gut and lung, in adult mice.

When these cells, called lymphoid tissue inducer cells, encounter an infection by Citrobacter rodentium, — a model of human E. coli infection in the gut — they send out a molecular alarm that is critical for early immune responses and draws in more specialized cells to fight the invasion. In animals depleted of lymphoid tissue inducer cells, the immune response was incomplete and the animals were more likely to die from the infection.

Artis' group also found that another group of immune cells, called innate lymphoid cells, are responsible not for fighting infection, but for helping repair tissues after an infection. Specifically, they found that these cells secreted a growth factor in the lungs of influenza-infected mice. The growth factor induced proliferation of lung cells, which allowed the tissue to heal. If either the innate lymphoid cells or their growth factor were missing, the animals had diminished lung function and poor lung repair.

Although the experiments were done in mice, the researchers have found similar cells in the lungs of healthy human lung tissue, suggesting a similar process occurs in people.

The innate lymphoid cells also help keep helpful bacteria where they belong. Humans have approximately 10-fold more bacteria in our bodies than we have human cells. But these helpful bacteria can be harmful if they stray from their appropriate compartment. Artis' team found that in mice lacking innate lymphoid cells, some of the helpful bacteria normally found in the gut migrated to peripheral tissues where they promoted unhealthy inflammation.

Innate lymphoid cells aren't all helpful though, according to collaborative work from Artis and Brian Kim, MD, clinical instructor of Dermatology. The team found an accumulation of innate lymphoid cells in the active lesions of patients with atopic dermatitis, more commonly known as eczema. Using a mouse model of atopic dermatitis they also showed that mouse innate lymphoid cells contribute to disease progression The results suggest immune cells may be a new therapeutic target for treating the development and severity of atopic dermatitis.

Share This Page: