Immunomodulating effect of blood transfusion: is storage time important?

TNF-alpha and IL-2 are important cytokines in macrophage and T-lymphocyte activity against infection and dissemination of malignant cells. We studied the influence of supernatants from stored whole blood and buffy-coat-depleted SAGM (saline, adenine, glucose and mannitol) blood in stimulating TNF-alpha and IL-2 release in an ex vivo assay.

Supernatants of 10 units of whole blood and 10 units of SAGM blood were collected after 1, 21 and 35 days of standard blood bank storage. Heparinized blood from 20 healthy volunteers (as 'recipients'), corresponding in ABO and Rh type to the stored blood, were used in a culture system with LPS and PHA as stimulators of TNF-alpha and IL-2 release. The effect of added supernatants, from either stored whole blood or SAGM blood, on cytokine release was evaluated compared to saline as control. TNF-alpha concentration was analyzed by ELISA after culture for 24 h and IL-2 after 72 h, respectively.

Supernatants from both stored whole blood and SAGM blood showed a significant decrease in both LPS- and PHA-stimulated TNF-alpha release that was dependent on storage time. IL-2 was not detected in response to LPS stimulation. PHA-stimulated IL-2 release was significantly reduced and related to storage time of both whole blood and SAGM blood.

Recipient cytokine release induced by blood transfusion seems to be dependent on storage time. This may have implications in transfusion-induced immune modulation.