Firstly, let me define what is stress and the types of stress. Stress is “a disruption in one’s psychobiological balance and sense of harmony within oneself and/or with the social and physical environments.” (Edlin and Golanty, 2010, P46) Stress could also be defined as a state of mental or emotional strain resulting from adverse or demanding circumstances. There are three types of stress which is Distress, Eustress and Neustress. Distress is a negative form of stress which occurs in reaction to something we perceive as bad. For example, distress negative emotions are extreme worry, sorrow or pain which would occurs in situations such as death, unemployment and conflict in interpersonal relationships. Eustress is a positive form of stress which have a beneficial effect on health and emotional well-being. In short, it is a beneficial stress. Eustress would occur through some events that happen in our life such as receiving a promotion at work, getting married, having a child and taking a vacation. Lastly, neustress is a neutral stress which we perceived as neither harmful nor helpful and has no consequential effect. The main types of immune cells are white blood cells. There are two types of white blood cells which are lymphocytes and phagocytes. When a person is under a condition of negative stress, his/her immune system’s ability to fight off antigens would reduce which results him/her more susceptible to infections. For example, my appetite tends to decrease before the exam period due to my stress on understanding every topic. With the decreasing of my appetite, it leads to poor nutrition and lack of nutritional energy which is used to support immune functioning and the function of the entire body. Therefore, stress weakens my immune system. This is because stress can cause an increase in corticosteroid which is a type of stress hormone that can supress the effectiveness of the immune system such as lowers the number of lymphocytes. Negative stress can also have an indirect effect on the immune system if a person uses unhealthy behavioural coping strategies such as consumption of excess alcohol, smoking and poor diet to reduce their stress. Another example of stress happened is when I have financial problems with high level of debt. High level of debt is due to phone bills, provide money for family as well as family expenses. Therefore, I would need to work after school, weekends and holiday period to cover my daily expenses as well as family expenses. This causes me to have insufficient sleep which leads my cells in my blood that fight infections are not working to keep infections at bay thus leading me often getting sick easily. In addition, heavy workload and debt also caused me to have lots of negative emotions appear such as depression, frustration and anxiety. When I am having these negative emotions, I would be unable to have relax myself therefore my stress increases causing my immune system to weaken. Before elaborating on how the immune system responds to stress, I would firstly define what is immune system and how is it build up. Immune system is our body’s defense against infectious organisms and other invaders. Through a series of steps which is called the immune response, the immune system attacks organisms and substances that invade body systems and cause disease. It is made up of a net of cells, tissues and organs. These work together to protect our body. Fight or flight response is our body’s response to perceived threat or danger. Certain hormones such as adrenalin and cortisol are released when this fight or flight response occur. This lead to some physical signs such as rapid heartbeat and breathing, pale or flushed skin and trembling which indicates the fight or flight response occur. Firstly, rapid heartbeat and breathing occurs when our body increase heartbeat and respiration rate. This increase is to provide energy and oxygen to our body which would be a need to fuel a rapid response to the danger. Secondly, pale or flushed skin occur when the stress response starts to take hold. This leads the blood flow to the surface areas of the body reduced and blood flow to the muscles, brain, legs and arms increased. In addition, our body’s blood clotting ability would also increase which helps to prevent excess blood loss when injury happens. Lastly, trembling occurs when someone faced stress or danger. This causes a person muscles to become tense and ready for action. In addition, chronic stress would lead fight or flight response occur. Post-Traumatic Stress Disorder (PTSD) is a form of chronic stress. Post-Traumatic Stress Disorder (PTSD) occur when a person experiences traumatic life event such as accident or natural disaster. For example, James had a bad car accident at the age of 10 which leads him to suffer from PTSD. James that suffer from PTSD may be stuck in chronic stress mode because their mind always believe that the threat is still present. Therefore, his body bombarded with the hormones that associate with fight or flight response causing both physically and mentally draining. In conclusion, stress would slow down the immune response and lengthen healing duration. High stress levels would reduce our immune system and it’s ability to defend our body from diseases.