Final answer:
Type II hypersensitivity reactions occur during incompatible blood transfusions, causing inflammatory responses and cell destruction. Anaphylaxis, a type I hypersensitivity reaction, is a severe, life-threatening allergic response requiring immediate treatment like epinephrine administration.
Step-by-step explanation:
In the context of blood transfusions, type II hypersensitivity reactions occur when there is an incompatible blood type or Rh factor transfusion. For example, if a type B individual receives type A blood, their anti-A antibodies will target the transfused red blood cells (RBCs), leading to agglutination and activation of the complement system. This triggers a strong inflammatory response and lysis of the RBCs, potentially causing serious complications such as fever, chills, urticaria (hives), dyspnea (breathlessness), and hemoglobinuria. In severe cases, it can result in shock, multi-organ failure, and death.
Another scenario is when an Rh-negative individual is exposed to Rh-positive RBCs. Initially, a primary antibody response takes time to develop, so the first exposure may not cause immediate harm. However, subsequent exposures can trigger a rapid secondary antibody response with serious hemolytic transfusion reactions (HTR) due to the presence of anti-Rh antibodies.
It is also important to understand anaphylaxis as a type of severe allergic reaction. Anaphylaxis can occur within minutes of exposure to the allergen, leading to symptoms like a drop in blood pressure and airway obstruction, which are life-threatening without immediate treatment such as epinephrine.