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In a new study, researchers from the School of Dental Medicine, together with an international team that includes colleagues at the Technical University of Dresden, layout the mechanism by which intrinsic immune memory can lead to a certain type of inflammatory disorder, in this instance, gum disease, to increase vulnerability to another, here, arthritis, through alterations to immune cell precursors in the bone marrow.

As indicated in a EurekAlert! report, the immune system remembers. Frequently, this memory primed by previous encounters with threats such as viruses or bacteria, is an asset.

However, when that memory is flashed by inner drivers like chronic inflammation, it can prove dangerous, memorializing a misguided immune response.

Bone Marrow Transplant

In a mouse sample, the researchers showed that recipients of a bone marrow transplant were predisposed to more severe arthritis if their donor suffered from inflammatory gum diseases.

According to a corresponding author on the work, Professor George Hajishengailis, from Penn Dental Medicine, even though they used periodontitis and arthritis as their model, their findings go above and beyond the examples.

This, in fact, is a central mechanism, a unifying principle that underlies the link between a variety of comorbidity.

In their study published in the Cell journal, the researchers noted that this mechanism may prompt a reconsideration as well, of how bone marrow donors are chosen as donors with specific types of immune memory resulting from underlying inflammatory conditions might put bone marrow transplant recipients at higher risk of inflammatory disorders.

Link Between Inflammatory Conditions

Essentially, rodent models with the induced periodontal disorder had more severe reactions as well, to a later immune system challenge, a trained immunity's evidence.

To put the entire picture together about the connection between inflammatory conditions, what Hajishengailis calls the "critical experiment," was a bone marrow transplant.

In a similar report, Medical Xpress specified that mice with periodontitis, a severe type of gum disease, served as donors, as did a group of healthy rats that serve as controls.

Moreover, 200 stem cells from their bone marrow were transplanted into mice that had never had gum disease and "which had had their bone marrow irradiated." After a few months, the said mice were exposed to collagen, which activates arthritis.

Implications of Bone Marrow Transplants

The researchers said the higher joint inflammation in recipient mice was because of the inflammatory cells that derive from the periodontitis-trained stem cells.

Further investigations proposed that the signaling pathway controlled by a receptor for the IL-1 molecule played an important role in adding to this inflammatory memory.

Mice lacking IL-1 receptor signaling could not induce the immune memory that made the recipient mice more vulnerable to comorbidity, the study investigators discovered.

The research has implications for bone marrow transplants in humans, a common course of treatment in dealing with blood cancers.

Organ Donor's Medical Background Affecting Recipient's General Health

Hajishengallis said that certainly, it's a great thing if one finds a matching donor for a bone marrow transplant. However, he added, their findings suggest that it is essential for clinicians to keep in mind how the medical background of the donor will affect the recipient's health.

Currently, follow-up projects are investigating how other inflammatory conditions may be associated with periodontal disease, a sign the study authors say, of how critical oral health is to one's general health.

The professor said, he is proud for the field of dentistry that the work, with importance to a wide range of medical conditions, initiated by examining oral health.

Related information about inflammation is shown on Osmosis's YouTube video below:

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