Respiratory ImmunityRespiratory tree

The respiratory tract is like mirror image of a tree but inside our body. The vegetable world around us is our natural counterbalance. Our lungs take in the oxygen which plants provide and they, in turn, take our carbon dioxide.

The lungs and the airways leading to them are particularly vulnerable to infections. The surface is huge - an area the size of a doubles tennis court. Fortunately, the passages which lead the outside air to the lungs are beautifully designed to trap dust, dirt, spores and potential pathogens like viruses, bacteria, and molds.

Anatomical Support for Immunity

The path through which the air travels on the way to the lungs is loaded with very effective traps which are physical in nature. It begins with the turbulence produced in the nasal passages. As the inspired air twists through these passages, it strikes the walls and many of the particles get trapped before they reach the lungs.

Mucus, produced by specialized cells lining the airway walls, is sticky and traps a great deal of the inhaled dust, pollen, bacteria, and viruses.

When we get a 'cold,' the increased mucus production aids us in eliminating the virus, thus promoting healing. In our zeal to reduce symptoms by resorting to medications to dry up these secretions we may be, inadvertently, prolonging the illness by reducing mucus, or by making the mucus drier and thus more difficult to expel. This hinders the elimination of viruses and possibly increases the risk of pneumonia.

In addition, many people with sinus symptoms during and after a respiratory illness make the situation worse by taking antihistamines or "cold and sinus" medications. These medications cause the mucus to become thick, and get stuck, which increases the pain by building up the pressure in the sinuses. The simple approach to relieve pain is to re-establish mucus flow. You can use inhaled steam, possibly with the addition of a little menthol (Vicks™), hot drinks and hot compresses on the affected area. Inhaled salt water (saline) can be purchased in any pharmacy and works very well to loosen dry, trapped mucus.

For centuries the people of India have used a neti pot which resembles a little tea pot, to deliver warm salty water to the nose which they then inhale. The salty water and the heat combine to loosen the mucus secretions, which may then be expelled. The frequent use of this device by the gurus of India may be explained by their heavy dairy consumption. Dairy consumption has been linked by some people to excess respiratory mucus production.

To return to the respiratory tract, the physical traps are responsible for the removal of almost all but the smallest particles, and even viruses, the smallest physical substance to which we are exposed.

Additional physical defenses of the respiratory tree Cilia

Further down the airway, in the trachea (about the diameter of a 25 cent piece), the bronchi, (10 cent size) and and into the bronchioles (pencil diameter), the mucus is lifted toward the throat by the constant waving of tiny hair-like projections called cilia (see above).

These ciliae have the same physical structure and the same type of motion as the tail of sperm except they always beat upward. They lift mucus and the trapped secretions in what is best described as the ciliary escalator.

When the mucus secretions, together with its trapped particles, reach the larynx, it is either coughed up or swallowed. A common problem is an excess of mucus which will be covered later on this page.

A further aspect of physical respiratory defense involves muscle fibres wrapped Pulmonary alveoli.around the respiratory bronchioles, the tiny airways leading to the lung exchange sacs, the alveoli. These strands of muscle respond to either open the airways, as when we exercise, or close them down, when we encounter a noxious substance in the air we breathe. In asthma, the wheeze heard is the air trying to get past bronchioles which have become constricted and are loaded with sticker than normal mucous.

Alveoli look like bunches of grapes hanging on their bronchioles, Their walls, which separate the air from our blood, are only one cell layer thick. Their thinness allows macrophages from the blood to squeeze through the capillary walls and into the air space of the alveoli where they eat viruses, bacteria and dust (and are sometimes called dust cells once they are full of dust or dead bacteria). These dust cells are then swept upwards into the bronchi where they eventually get coughed out. Studies have demonstrated that, when we're healthy, even very fine inhaled particles will be coughed out in from 2-4 hours.

The Immune System in the Respiratory Tree

In addition to the complex physical safeguards which the respiratory tree provides for us, there are also countless islands of immune tissue along the way to protect us. The tonsils - those little buds of lumpy tissue in the back of our mouth are one of the first of these islands. They are the most visible of these collections of lymph tissue referred to as MALT (mucosal associated lymph tissue) which are found in the nose and all the way down to the the alveoli.

Immune defense depends on the integrity of the whole body, but mucus plays an important role in the process. Mucus, created by the goblet cells (darker blue in the illustration), serves not only to transport trapped particles, but also holds antibodies created by the immune cells. These antibodies are made in response to processes in the dendritic cells (yellow) which 'eat' viruses and bacteria, decode their information, then pass this on to lymphocytes which create the antibodies, then pump them into the mucus layer. These (secretory IgA) antibodies are the largest part of our immune system. IgA is produced in greater quantities in the digestive system and is the primary defense of the respiratory system. IgA lies in wait to trap viruses and bacteria.

The illustration helps to give an idea of the surface lining our airways. Respiratory EpitheliumThe complex combination of physical and immune processes give us the ability to safely exist in a world teeming with potential problems.


When we get a 'cold', usually a rhinovirus, our body responds with a sore throat (virus attaching itself to the epithelium in the throat), a fever (the immune system kicking in and activating its defenses), and sneezing and coughing (mucus going to work to rid us of the virus). We get tired (our body asking for some time to deal with the invader). If we answer this challenge with rest, increased fluids and a reduction in mucus forming foods (dairy and baked flour products), we usually get better quickly.


With a flu, the same situation applies except the flu viruses are much stronger and the need for rest is greater. In the illustration below, it is clear how much the healthy cilia (on the left) have been altered by flu. These damaged cilia are virtually unable to clear any mucus, so our body responds with coughing to help.

before and after influenza a


Treatment Suggestions

Some of the things we do to get some relief from the symptoms of our illness can make the situation worse. Not resting is one of the worst of these. Medication to dry out the respiratory secretions (antihistamines) cause our body to lock in the mucus and slow down healing.

One of the frequent complaints I see in the clinic is what patients often call "sinusitis." Their symptoms are facial pain and headache, without fever, and is caused by locked in mucus. Patients often feel this pain will be fixed by an antibiotic, which is not usually required.

The fix is to stop the antihistamines and decongestants which have dried our the secretions. Blocked secretions cause the pressure to build, creating pain. The best treatment, in my opinion, is to inhale steam, perhaps containing a little camphor (Vicks™).

It is very important not to use Vicks™ on an infant or small child because its use in children has been linked to respiratory distress, and even, death.

It also helps to apply hot wet compresses to the face, to take a hot drink, and to snort salt water up the nose.

How to make a Salt Water for Inhalation

You can purchase this as a saline spray or make it yourself. Saline water is made by adding 1/8 teaspoon of salt in 1/4 cup of good quality water. Please use spring or distilled water for this. Tap water with it's chlorine can be an unwanted irritant. Sinus congestion can almost always be helped without requiring an antibiotic.

If you have a fever and are coughing green or bloodstained mucus and especially if you feel exhausted and short of breath, then you might have pneumonia, and an antibiotic might help. I usually prescribe azithromycin (Zithromax®) because it usually works and between the daily doses, one can take probiotics.

Alternative Approaches

Some people with an upper respiratory (viral) infection seem to respond well to natural remedies, including herbal teas and compounded herbal preparations as well as homeopathic ones like Oscillococcinum®. There are a wide range of natural cough remedies which do not contain potentially harmful ingredients. Nova has a useful homeopathic product called 'Respiratory' which should be available in health food stores.

Some people may develop a wheezy cough during or after a viral infection. A physician may opt to treat this wheeze with an inhaled steroid/bronchodilator (asthma puffer). This can have the effect of relieving the dry wheezy cough. Alternative herbal teas and a change of diet can also help.


Diet Suggestions

Stopping bread products and dairy products can make a difference with the symptoms of fever and colds, because these foods seem to increase mucus production. Drinking lots of hot teas and soups support mucus elimination.

Also see Strengthen Your Immunity

If your symptoms are more sinus?

If you would like to reduce the number of colds and flu's.