Our immune system is very complicated, with many factors at play. One aspect of autoimmune disease is the relationship between Th1 and Th2. To simplify autoimmune disease to my patients, I use a simple balance-scale analogy to describe the impact of Th1 and Th2 on the immune system, and subsequently autoimmune disease.
First, Background on Immune Function
Our immune system is the thing that helps us fight off infection. We rely on it to turn on when we have an infection, and then turn off when the invading pathogen is gone. There are many different cells involved in this process, but one of them is called a CD4+ T helper cell. Within the realm of CD4+ T helper cells, there are a four types of cells, as shown in Figure 1. All four play roles, but only two will be of focus in this article: TH1 (aka Type 1) and TH2 (aka Type 2) cells. The effects of TH1 and TH2 CD4+ helper T cells vary drastically and have established relationships to allergies and autoimmune disease. A follow-up article to this will highlight the roles of Th17 and Treg cells.
Science Alert! The way these Th1 and Th2 cells work is by releasing chemical mediators called cytokines. TH1 T helper cells produce INF-γ, IL-2 and TNF-β, which evoke cell mediated immunity and phagocyte-dependant inflammation. TH2 helper T-cells produces IL-4, IL-5, IL-6, IL-9, IL-10, IL-13 – evoking strong antibody responses .
The Scale Analogy & Healthy Immune Function
Figure 2: Th1 and Th2 should be balanced for optimal health.I describe the whole Th1 and TH2 aspect of our immune system as a balance-weight scale. Figure 1 demonstrates this analogy: there are two arms to the scale, Th1 on one side, balanced by Th2. In optimal health, they are in balance.
Th1 deals with viral and bacterial infections. It’s the body’s first response to pathogens. It relies on other cells to kill the invading pathogen – hence we call it cell-mediated. We call this the innate immune system and it’s associated with inflammatory reactions.
Th2 deals with infections too – particularly parasitic infections. The Th2 cells rely on antibodies to do their work – hence we call this anti-body mediated. Th2 tends not to be inflammatory.
When we get sick, one arm of this system may ‘turn up’ – or become dominant. This is a normal physiologic response in order to fight the infection off. It’s important to note that once the infection is gone, the arm that was turned up will turn back down.
Th1 and Th2 in Dysfunction
Environmental factors and genetics will determine the balance of Th1 and Th2 . Although a balanced scale is optimal, some people will have Th1 or Th2 dominance even when there is no pathogen around. The genetic and environmental influences are what make people so variable in how they respond to pathogens. This is one reason why some people suffer allergies or some are constantly getting sick, all while others go years without getting even a cold.
Conditions associated with Th1 Dominance
The following are related to Th1 dominance, as determined through cytokine profiles and other scientific research.
- Organ-specific autoimmune disorders 
- Some unexplained recurrent abortions 
- Alzheimer Disease
- Low T3 syndrome  
- Guillain-Barre syndrome
Conditions Associated with Th2 Dominance
FThe following are related to Th2 dominance, as determined through cytokine profiles and other scientific research.
- Systemic autoimmune disorders 
- Allergies  (hives, hay fever, nasal drip, mucus)
- Histamine intolerance 
- Airway constriction
- Atopic disorders
The next article in this series, will address how we can go about balancing the Th1 and Th2 immune system. The aim in treatment is to first identify whether a person is Th1 or Th2 dominant through both signs and symptoms as well as lab testing in come circumstances. Next, to treat we focus on many lifestyle factors. Certain foods, herbs and supplements can affect the balance, so I work with my patients to determine how to go about balancing their immune system. The next article in this series will also address why some probiotics may make certain patients worse, as they too affect this Th1/Th2 balance.
The next article will be coming soon!
About the Author
I'm Johann de Chickera, a Naturopathic Doctor, practicing in Ontario, Canada. My clinical practice relies on keeping up with the most up-to-date research and continued education. This blog serves as a way to provide others with a compilation of everything I've learned along the way. Please click here if you're local and want to see me in practice.