The adaptive immune system is one of the two main branches of the immune system, alongside the innate immune system.

Adenosine triphosphate (ATP) is a complex organic chemical that is involved in energy transfer within cells.

Anaphylaxis is a severe and potentially life-threatening allergic reaction that occurs rapidly and affects multiple body systems.

Anticoagulants are medications that prevent the formation of blood clots in the body.

A blood bank is a center where blood gathered as a result of blood donation is stored and preserved for later use in blood transfusion.

Blood donation is the process of voluntarily giving blood, either for storage in a blood bank or for immediate use by a patient.

A blood transfusion is a medical procedure where blood is transferred from one person (the donor) to another person (the recipient).