What's the relation between histamine and gluten intolerance?

A short while ago, I was alerted to research that is being conducted on histamine intolerance. The reason it piqued my interest was the remark on how perceived gluten intolerance may in reality be a case of histamine intolerance. The researchers that were interviewed spoke about probiotics being developed to 'cure' histamine intolerance.

Therefore, without further ado, an explanation on what histamine intolerance really is.

What is histamine?

Histamine is an extremely important bioactive chemical that is indispensable in the efficient functioning of many body systems. It is a neurotransmitter and is involved in the regulation of stomach acid, the permeability of blood vessels, muscle contraction, and brain function.
In humans, the highest histamine concentrations are found in the skin, lung, and stomach, with smaller amounts in the brain and heart.

Histamine is also essential in defending the body against invasion by potentially disease-causing agents such as bacteria, viruses and other foreign bodies.

Histamine is made and stored within white blood cells such as mast cells.
When the immune system is activated in response to foreign material entering the body, histamine is the first "defense chemical", or more correctly, inflammatory mediator released in the process called inflammation. Inflammation is the clinical evidence that the immune system is responding to a potential threat to the body. Histamine is always present when inflammation occurs, and excess histamine will result in symptoms that resemble inflammation.

In addition to its role in controlling vital body processes and defending against foreign invaders, histamine is a key mediator in the symptoms of an allergic reaction. Since allergy is essentially an inflammatory reaction, histamine, together with other protective inflammatory mediators is released in response to the allergen.
Allergens are components of living cells that in themselves are harmless, such as plant pollens, animal dander, mould spores, dust particles, dust mites, and foods. An allergic reaction to these "foreign but harmless" substances occurs when the immune system mistakes these innocuous materials for a potential threat.