Talk:Transfusion-related immunomodulation

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The topic of transfusion immunomodulation (the "related" is redundant and thus unnecessary) is actually of considerably greater importance in medicine and broader in scope than one might think. With the exception of life-threatening hemorrhage, the only convincing evidence for the benefit of transfusion therapy as currently practiced is in preventing recurrent stroke in sickle cell disease. The rest of medical uses of transfusion remain of uncertain benefit to risk ratio. What has been definitively demonstrated is that in most clinical situations, the patients who are transfused do considerably worse than those not transfused and those who get more transfusions almost always do worse than those getting fewer transfusions. While some of this effect is due to ascertainment bias (sicker patients get transfused or receive more transfusions), the cause and effect nature of these observations is virtually certain. Some of the effects demonstrating some or all the conditions for cause and effect (dose dependence, reproducibility, biologic plausibility, etc.) include increased post-operative infections (ameliorated in part by leukoreduction or use of autologous transfusions in randomized trials), increased allograft survival, decreased spontaneous abortions, decreased severity of inflammatory bowel disease, increased acute lung injury, increased myocardial infarction and other thrombotic complications, etc. Thus transfusion immunomodulation has been broadened to encompass not only decreases in cellular adaptive immunity but inappropriate activation of innate inflammatory immunity and the hemostatic system, including platelets. Fortunately, some of these effects can in part be mitigated by leukoreduction of blood transfusions or avoidance of blood transfusions. Additional promising preliminary research demonstrates that removal of supernatant plasma from stored transfusions may have beneficial effects. Clearly there are both cells and small molecule biologic mediators in stored donor blood that modulate not only recipient immune function, but hemostatic and organ specific functions. This is one of the more important research agendas in transfusion medicine in terms of clinical outcomes for patients, which has been recognized by the NIH directing its research funds into this area of research beginning in 2008.

For a recent history of this subject, see the commentary below.

Blumberg N. Deleterious clinical effects of transfusion immunomodulation: proven beyond a reasonable doubt. Transfusion. 2005 Aug;45(2 Suppl):33S-39S.

2014 Update: The role of allogeneic transfusion in causing increases in nosocomial infections is now clear. Randomized trials of leukoreduction demonstrate a 30-40% reduction in post-operative infections in transfused patients receiving only leukoreduced red cells. (1,2) Recently, it has been demonstrated that restrictive red cell transfusions are associated with a 10-20% reduction in nosocomial infections compared with liberal red cell transfusions (3). The combination of leukoreduction and restrictive transfusion appears to be additive. Nosocomial infection is likely the most common serious adverse event associated with red cell transfusion, with 1-2% of transfusions leading to such infections.

(1)Transfusion of leukoreduced red blood cells may decrease postoperative infections: two meta-analyses of randomized controlled trials.

Fergusson D, Khanna MP, Tinmouth A, Hébert PC.

Can J Anaesth. 2004 May;51(5):417-24.

(2)The intention-to-treat principle in clinical trials and meta-analyses of leukoreduced blood transfusions in surgical patients.

Blumberg N, Zhao H, Wang H, Messing S, Heal JM, Lyman GH.

Transfusion. 2007 Apr;47(4):573-81.

(3)Health care-associated infection after red blood cell transfusion: a systematic review and meta-analysis.

Rohde JM, Dimcheff DE, Blumberg N, Saint S, Langa KM, Kuhn L, Hickner A, Rogers MA.

JAMA. 2014 Apr 2;311(13):1317-26. doi: 10.1001/jama.2014.2726. Review. Widefox; talk 22:50, 30 September 2015 (UTC)