Allergies, asthma and eczema: The Th1/Th2 story

It’s spring here in Missoula and you know what that means: hay fever season is just around the corner. If you’re a hay fever sufferer and you feel like the only way to cope is to dress yourself in a hazmat suit then you probably want to read on.  Ditto if you have asthma, eczema or food allergies (the anaphylactic kind).

Allergies, asthma and eczema are all interrelated.  In fact, many patients who have one of these symptoms actually have all three. This blog post will explain why these issues are primarily an immune-system balancing problem.  Skip the first part if you struggle with biology and immunology.

What is Th1 and Th2? What does this have to do with my immune system?

The immune system is a complex, integrated collection of cells and chemicals that protects against disease.  The primary function of the immune system is to recognize the difference between normal cells (“self”), and invaders (“non-self”).  The immune system must then protect “self” and work to eliminate “nonself,” which can include viruses, bacteria, parasites, even cancer cells.   The human body has an incredibly intricate system of defense, and uses multiple mechanisms to keep invaders (pathogens) out.

One of these mechanisms is called the adaptive immune system.  The adaptive immune system consists of special types of white blood cells called B cell and T cells (often called lymphocytes).   B cells make antibodies against foreign invaders so the immune system can “remember” the pathogen and quickly eliminate it in the future.  T cells are responsible for either actively killing (killer T cells), or helping to kill (helper T cells) the pathogen.

T lymphocytes activate and regulate the immune system by making cytokines, which are chemical signals that tell other cells in the immune system what to do.  Of all the types of cells in the body, helper T cells are considered to be the biggest producers of these cytokines.  There are two main types of helper T cells: Th1 cells and Th2 cells.

Th1 cells work to eliminate invaders that occur inside our cells (viruses and some intracellular bacteria).  Th2 cells aim to destroy pathogens that occur outside our cells (bacteria and parasites).  Th1 cells and Th2 cells each create different cytokines which triggers different effects in the body.

Why is this important?

A healthy immune system can “choose” which types of cells to produce and can easily switch back and forth between Th1 and Th2-type responses.  An unhealthy immune system can get “stuck” in one of these responses – leading to excessive production of only one type of cytokines.

Most people in the developed world get “stuck” in a Th2 response.  This is because our bodies are not exposed to as many parasites and bacteria as in the past (thanks to Lysol, toilets, and water sanitation systems).  An immune system without an invader to fight will start attacking anything it can – pollen, food particles, dust, dander, etc.  When Th2 becomes switched on it activates eosinophils and IgE-type reactions which leads to the symptoms we recognize as “allergies”.  For some people this can become severe, leading to asthma, eczema, and anaphylactic reactions.

Much of the balancing of the Th1/Th2 response occurs in pregnancy and early infancy.  Once the immune system gets “stuck” in an abnormal pattern we have a much more difficult time correcting it.  This is why treatments that aim to balance the Th1/Th2 ratio can take a long time to work.  It is very important to stick with it to see results!

How can I balance my immune system?

Naturopathic doctors have several strategies to balance an “unhealthy” immune system:

Probiotics and prebiotics.

“Probiotics” refers to beneficial bacteria that normally reside in healthy human intestines.  “Prebiotics” refers to the types of food that promote the growth of these healthy bacteria.  Probiotic bacteria have been shown to alter Th2 cytokine production in both healthy and “allergic” people.  Probiotics also appear to stimulate the immune system in the gut called GALT (Gut-associated lymphatic tissue) which promotes healthy immune activity.

Fish oil.

Fish oil blocks inflammatory cytokines by reversibly binding to immune system enzymes. Reversible is good!  This means that when the body needs an appropriate immune response it can still have one.  For fish oil it is absolutely essential that you buy a high quality product – they are frequently contaminated with mercury (since some types of fish are high in mercury).  I like one called Finest Pure Fish Oil from Pharmax, which seems to be pricey but actually has the highest concentration of EPA and DHA per dollar.  Nordic Naturals is good too.  (No affiliation with these products, just for your information.)  They can be hard to find, e-mail me if you need helping locating them.

Vitamin A and vitamin D.

Vitamin A, in combination with appropriate amounts of vitamin D, seem to be able to turn off inflammatory immune responses.  The combination of these two nutrients can take immature T-helper cells and switch them to an anti-inflammatory version called T-regulatory (T-reg) cells.  This can be helpful for patients who have either excess Th2 OR Th1 responses.  BUT – please note that vitamin A and vitamin D, which are both steroid molecules, can be toxic in high levels.  You always need to consult a physician before you take either of these vitamins in levels higher than recommended by the FDA (the “daily recommendation”).

Herbs, fungi, etc.

Naturopaths have a long botanical formulary: ~300 herbs, many of which are anti-inflammatory or immune modulating.  There are lots of options for herbal formulations to alter your Th1/Th2 ratio.  That could fill up a whole blog post itself, so e-mail me or schedule an appointment if you have more questions.

Naturopathic doctors have many other tricks to balance the immune system – usually it depends on the individual and their own particular biochemistry.  Don’t give up if the first thing you tried didn’t work!  Every time a patient comes to me and something hasn’t worked it just gives me more information.  There are many different types of biochemistry – we just have to figure out what works for you as an individual.

Here’s two of many references I used for this:
Ghadimi D, et al. “Effects of probiotic bacteria and their genomic DNA on TH1/TH2-cytokine production by peripheral blood mononuclear cells (PBMCs) of healthy and allergic subjects. Immunobiology. 2008;213(8):677-92.

Abrahamsson TR et al, A Th1/Th2-associated chemokine imbalance during infancy in children developing eczema, wheeze and sensitization.  Clin Exp Allergy. 2011 Dec;41(12):1729-39. doi: 10.1111/j.1365-2222.2011.03827.x. Epub 2011 Aug 1.

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