Our microbiota is determined by many variables including ABO blood groups. The microbiota is not only confined to the gut and skin but is also recoverable from blood of healthy donors. The microbiota shape our immune system through cross reactivity with antigens, the expression of direct molecular patterns, the release of cytokines, the effects on nutrients and micronutrients and even through an interplay with epigenetics. It is likely, therefore, that a donor's microbiota could alter the antigenicity of blood and its components and potentially contribute to transfusion-related immune modulation [TRIM]. It could also potentially transmit infections. The recipient's microbiome contributes, on the other hand, to the tolerance to transfused blood, or to the development of transfusion reactions. Cancer patients are a particularly vulnerable population, often immunosuppressed with a significantly altered microbiota. They are more at risk for transmission of “dormant” bacteria via blood transfusion. Furthermore, chemotherapy and radiation induce mucositis that likely results in significant translocation of gut microbiota and abnormal immune reactions to transfused blood. It is therefore relevant to revisit transfusion thresholds and consider transfusion-saving strategies in cancer patients.
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