NR 507 Week 1 Assignment: Immune Response

Unit 1 Immune response

1. What of the following is considered the first responders of the innate immune systems? Neutrophils
2. Allergic contact dermatitis is an example type 4 of a Hypersensitivity reaction. Allergic contact dermatitis is an example of a Type IV hypersensitivity reaction mediated by T-cells. When the individual comes in contact with the antigen (e.g. poison ivy), an antigen complex is formed. On subsequent exposure to the antigen, sensitized T-cells activate the inflammatory process that causes the allergic contact dermatitis to appear.
3. Hives (Urticaria ) are an example of a Hives (urticarial) are an example of a Type 1 hypersensitivity reaction mediated by the antibody, IgE, and mast cells.
4. Type 2 hypersensitivity reactions are mediated by The Type 2 hypersensitivity reaction is mediated by IgG or IgM.
5. Anaphylaxis is a hypersensitivity reaction. Type 1 hypersensitivity reactions are mediated by IgE and mast cells. An individual who is highly sensitized to the antigen may experience anaphylaxis.
6. Examples of type II reactions include drug allergies, hemolytic anemia, blood transfusion mismatch with resulting transfusion reaction, and Rh hemolytic disease.
   • The cell to be destroyed by the antibody
   • Cell destruction through phagocytosis by macrophages
   • Damage to the cell by neutrophils triggering phagocytosis. Natural killer cells release toxic substances that destroy the target cell
   • Malfunction of the cell without destruction

Type III Immune-Complex Reaction The Type III hypersensitivity reaction is also an antigen-antibody response. The major difference between Type II and Type III responses is that in a Type II response, the antibody binds to the antigen on the cell surface, but in Type III responses, the antibody binds to the antigen in the blood or body fluids and then circulates to the tissue. Type III reactions are not organ specific and use neutrophils as the primary effector cell. In Type III hypersensitivity reactions, immune-complex deposition (ICD) causes autoimmune diseases, which is often a complication. As the disease progresses, more accumulation of immune-complexes occurs, and when the body becomes overloaded the complexes are deposited in the tissues and cause inflammation as the mononuclear phagocytes, erythrocytes, and complement system fail to remove immune complexes from the blood. One of the classic Type III reactions is serum sickness.

Serum Sickness Immune complexes are formed in response to an antigen (Amoxicillin) that has been taken into the body. These complexes embed themselves into the vascular endothelium causing vasculitis and tissue injury as a result of complement. The skin and joints are most commonly affected. Fortunately, the condition is self-limiting.

Type IV Cell-Mediated, Delayed Reaction The type IV hypersensitivity reactions are known as cell-mediated responses and use lymphocytes and macrophages as primary mediators. Unlike the first three types of responses, which are humoral immune functions, a Type IV response is mediated by T-lymphocytes and does not use antibodies. A typical reaction from a Type IV cell-mediated response would be a localized contact dermatitis. When the individual comes in contact with the antigen, T-cells are activated and move to the area of the antigen. The antigen is taken up, processed, and presented to macrophages, leading to epidermal reactions characterized by erythema, cellular infiltration, and vesicles. This process is illustrated in contact dermatitis on the next page.

Contact Dermatitis is a classic type IV hypersensitivity reaction that occurs after exposure to the skin. The symptoms typically appear a few days later. This is a T-cell-mediated response that is initiated when the individual comes into subsequent contact with the antigen. It is possible that he has been exposed prior to the appearance of the rash. On the current exposure, the T-cell recognized the antigen and causes the classic immune reaction. The macrophages begin phagocytosis which leads to the skin reaction of erythema and the formation of vesicles. To reduce the itching and rash, a high potency steroid topical cream can be prescribed. Sometimes systemic steroids may be indicated if a large area of the face or other body surfaces are involved.