1. Stress And The Immune System.

2. The main types of immune cells are white blood cells
The main types of immune cells are white blood cells. There are two types of white blood cells – lymphocytes and phagocytes.
When we’re stressed, the immune system’s ability to fight off antigens is reduced. That is why we are more susceptible to infections.
The stress hormone corticosteroid can suppress the effectiveness of the immune system (e.g. lowers the number of lymphocytes). 
Stress can also have an indirect effect on the immune system as a person may use unhealthy behavioural coping strategies to reduce their stress, such as drinking and smoking. 
Stress is linked to: headaches; infectious illness (e.g. ‘flu); cardiovascular disease; diabetes, asthma and gastric ulcers.

3. Stress responses increase strain upon circulatory system due to increased heart rate etc. Stress can also affect the immune system by raising blood pressure.