Stress-related Illness: The Immune System

Designed to defend body against millions of antigens(i.e. bacteria, viruses, toxins and parasites).

3 different ways: * create a barrier that prevents antigens from entering your body. *If an antigen (virus) does get into the body, the immune system tries to eliminaate before it reproduces. *If the virus is able to reproduce and start causing problems, immune system is responsible for elimminating it.

Most important psrt of immune system, white blood cells(leucocytes). These are produce in bone (B-bone cells) marrow. Some stay here while others migrate to thymus gland(T-thymus cells), spleen or lypmh nodes for storage. Macrophages are another type of cell in immune system. Often referred to as scavengers (pick up and ingest foreign materials, or as antigen-presenting cells).

A specific B cell is tuned to a specific antigen, & when that antigen is present in the body the B cell produces millions of specialised immune proteins(antibodies) to eliminate it, this type of immune response is known as Th2 immunity. T cells are responsible for more aggressive form of immunity, detecting cells in body that are harbouring antigens. When they detect such a cell, they bump up against it and destroy both the antigen and the cell. This is know as Th1 immunity. Natural kille cells are an important part of Th1 response, and protect against cancer cells as well as viruses.

Th1 and Th2 are counter-regulatory. When one branch is active it produces chemicals called cytokines that inhibit action of teh alternate branch. This is so the body is able to maintain a balance between 2 types of immune response with Th2 active during the day and Th1 during night. Stress can influence balance between these two branches so that one inhibited more than the other. Eg- chronis stress, characterised by repeated HPA activation, is associated with a shift away from Th1 immunity towards Th2 immunity to ward off cancer.

(Acute) short lived stressors found a decrease in ummune cellfunction

Found higher lymphocyte(immune cell) couunts in Apollo astronauts during splashdown.

Studies effects of unemployment in Sweden, and found a decrease in lymphocyte rsponse to antigens.

Natural exp, what- investigting whether acute stessors(examination) had impact on immune system functioning in medical students. How- blood sample taken 1 month before(low stress) and during exam period itself (high stress). Immune system functining was assessed by measuring NK cell activity in blood samples. Found- NK cell activity was significantly reduced in 2nd blood sample compared to 1 month before. Suggest- short-term, predictable stressors reduce immune system functioning, increasing vulnerability to illness.

How- inflicted a 'punch biopsy' in the mouth of students either during summer holidays or 3 days before an exam. Found- wounds given before the exam took 40% longer to heal than wounds during the holidays.

How- tested impact of interpersonal conflict on wound healing. Found- blister wounds on arms of married couples healed moer slowly after they had discussions which were conflicting rather than supportive.

How- compared women separated from their partners with matched married controls. Found- poorer immune system functioning in women who had separated during the last year.

How- studies 90 newly wed couples over 24 -hour period. Asked to discuss and resolve marital issues likely to produce conflict (finances). Found - marital conflict produced significant changes in adrenaline and noradrenaline, which could lead to poorer immune functioning.

How- looked at activity of antibody slgA which coats the mucous surfaces of teh mouth, lungs and stomach, and helps protect against infection. Arranged students to give talks to other students (acute stress). Found- increase in slgA, whereas levels of slgA decreased during exam periods which streched over several weeks. Suggests: stress may have two effects on the on the immune system: up-regulation (increased efficeincy) for short-term acute stress snd down-regulation for chronic stress.

How- Meta-analysis of 293 studis conducted over past 30 yrs. Found: Acute stressors can boost the immune system, prompting it to ready itself for infections or other challenges to the integrity of the body. Chronic stressors led to suppression of immune system - most chronic stressors were associated with the most global suppression of teh immunity. The longer teh stress, the more the immune system shifted from potentially adaptive changes to potentially detrrimental changes.