An introduction to chemokines and their roles in transfusion medicine.

Chemokines are a set of structurally related peptides that were first characterized as chemoattractants and have subsequently been shown to have many functions in homeostasis and pathophysiology. Diversity and redundancy of chemokine function is imparted by both selectivity and overlap in the specificity of chemokine receptors for their ligands. Chemokines have roles impacting transfusion medicine in haematopoiesis, haematologic malignancies, transfusion reactions, graft-versus-host disease, and viral infections. In haematopoietic cell transplantation, chemokines are active in mobilization and homing of progenitor cells, as well as mediating T-cell recruitment in graft-versus-host disease. Platelets are rich source of chemokines that recruit and activate leucocytes during thrombosis. Important transfusion-transmissible viruses such as cytomegalovirus and human immunodeficiency virus exploit chemokine receptors to evade host immunity. Chemokines may also have roles in the pathophysiology of haemolytic and non-haemolytic transfusion reactions.