Asthma

Asthma comes from the Greek word for “panting”, which makes sense because it causes chronic inflammation of the airways, making them narrow and more difficult to breathe through.

People with asthma can have asthma exacerbation or asthma attacks, which are usually triggered by something in the environment which causes immune cells to generate inflammation in the lungs which can make them even narrower and potentially be life-threatening.

So, if we take a look at the lungs, you’ve got the trachea, which branches off into right and left bronchi, and then continues to branch into thousands of bronchioles.

In the bronchioles you’ve got the lumen, the mucosa, which includes the inner lining of epithelial cells, as well as the lamina propria, and the submucosa which is where the smooth muscle lives.

The molecular pathway that leads to asthma is actually pretty complex but it is often initiated by an environmental trigger.

In asthma there is often an excessive reaction from type 2 helper cells or Th2 cells against specific allergens.

Th2 cells, are an immune cell subtype, which are known to be involved in asthma, as well as atopic dermatitis, and allergic rhinitis, making up what’s called the atopic triad.

What can happen with asthma is allergens from environmental triggers, like cigarette smoke, are picked up by dendritic cells which present them to a Th2 cell which produce cytokines like IL-4 and IL-5 leading to a number of features of asthma.

For example IL-4 leads the production of IgE antibodies which coat mast cells and stimulate them to release granules containing things like histamines, leukotrienes and prostaglandins. IL-5, on the other hand, activates eosinophils which promote an immune response by releasing more cytokines and leukotrienes.