Describe the role and function of basophils in the immune system, including their mediators and the reactions they cause.

Basophils are a type of white blood cell that are non-phagocytic, meaning they do not engulf other cells or particles. They are similar to mast cells and play a crucial role in allergic reactions. Basophils release various substances, including heparin (an anticoagulant), histamine (which causes vasodilation and increased vascular permeability), leukotrienes, bradykinin, and serotonin. These mediators cause local vascular and tissue reactions, leading to immediate-type hypersensitivity reactions. These reactions can manifest as mild symptoms like urticaria (hives) and rhinitis (hay fever) or severe, life-threatening conditions such as anaphylactic shock.