Blood transfusions downregulate hematopoiesis and subsequently downregulate the immune response

Abstract

BACKGROUND: Blood transfusions are associated with numerous clinical phenomena attributable to reduced posttransfusion immunocompetency. The exact mechanism by which blood transfusions induce a state of reduced immune responsiveness remains unclear. STUDY DESIGN AND METHODS: The effect of a large-volume blood transfusion on the frequency and responsiveness of immune cells in lymphoid compartments was examined in normovolemic rats. The effects of syngeneic and allogeneic blood transfusions were compared. RESULTS: The results in normovolemic rats were compared to those in nontransfused and saline-infused animals. In the normovolemic rats, there was a significant decrease in cells of erythroid lineage in bone marrow, with a slight increase in the percentage of cells in the bone marrow myeloid and lymphoid lineages; a significant increase in the percentage of the OX7+ Thy1+ cell population in bone marrow cells (stem cells are contained in this population) and blood cells; a decrease in the bone marrow OX6+ cell population (HLA class II-positive cells); a decrease in the responsiveness of blood, spleen, lymph node, and bone marrow cell populations to mitogens; and a downregulating effect of both syngeneic and allogeneic blood transfusions on hematopoiesis and cell responsiveness. CONCLUSION: Massive whole blood transfusion, either syngeneic or allogeneic, constitutes a strong downregulating signal for hematopoiesis, affecting the erythroid, myeloid, and lymphoid cell lineages. It leads also to an attenuation of the responsiveness of hematopoietic tissues to mitogenic stimuli.