Chronic stress can lead to a dominance of the T-helper 2 (Th2) immune response due to its effects on the body's immune system balance. Here's how it happens:
1. Stress Response Activation: When the body is under chronic stress, it constantly activates the stress response system, including the hypothalamic-pituitary-adrenal (HPA) axis. This leads to increased production of cortisol, a stress hormone.
2. Cortisol and Immune System Modulation: Cortisol has a modulating effect on the immune system. It is known to suppress the T-helper 1 (Th1) immune response, which is responsible for fighting off viruses and other pathogens. This suppression is a part of the body's attempt to prevent an overactive immune response, which can cause inflammation and tissue damage.
3. Shift towards Th2 Dominance: With the Th1 response downregulated, the balance shifts towards a Th2-dominant immune response. The Th2 cells are primarily involved in stimulating antibody production to fight extracellular parasites and bacteria. However, a Th2 dominance can lead to an increased susceptibility to viral infections and the development of allergic reactions and conditions such as asthma and eczema, as the body is less equipped to handle intracellular pathogens and more prone to overreact to harmless substances.
4. Chronic Inflammation: Chronic stress and the resulting Th2 dominance can also contribute to a state of chronic inflammation. While Th2 responses are generally anti-inflammatory, the imbalance and constant activation of the immune system can lead to a state where inflammation is not adequately controlled, contributing to the development of various chronic diseases.
5. Feedback Loop: The imbalance in the Th1/Th2 response can further exacerbate stress and inflammation, creating a feedback loop that makes it difficult to return to a balanced immune response.
In summary, chronic stress leads to Th2 dominance through the suppression of Th1 immune responses via cortisol-mediated modulation, shifting the immune balance towards Th2 and potentially contributing to increased susceptibility to certain infections, allergies, and chronic inflammatory conditions.