Test models » Whole blood cultures

Whenever testing the performance of leukocytes from volunteers or patients it has to kept in mind that the procedure used to isolate these cells as well as their preparation for different tests (e.g. the determination of cytokine synthesis in isolated leukocyte cultures or of CD-markers in flow-cytometry) usually causes a loss of current activities or the artificial induction of new ones.
Another drawback of cultures of isolated leukocytes or – even worse – sub-populations hereof is that these cells are only able to set up a fraction of the multi-layered signalling network required for a sufficient inter-cellular communication (as would be the case in vivo).
Even the smallest (and in most instances almost completely neglected) "cellular" elements of the blood, the platelets, contribute substantially to this messaging network. They not only secrete arachidonic acid metabolites (prostaglandins, leukotrienes, lipoxins, etc.), but also modify the expression of important activating receptors on leukocytes.
Not less important, the availability of biologically active cytokines in the cultures is strongly modified by enzymes released from activated neutrophil granulocytes.
Last, but not least, also red blood cells contribute to the development of an in vivo like condition by forming buffer surfaces for excess mediators.
These examples demonstrate clearly the importance of having all active elements of the blood present in experimental cultures. Only this way artificial findings can be avoided. This is particularly true in the pre-clinical and clinical evaluation of immunologically active drugs (anti-inflammatory substances, immunosuppressors, immunomodulators, adjuvants, vaccines etc.).
Another critical issue in the experimental detection of cytokines is the choice of methods by which this is accomplished. Despite the wide spread use of mRNA based technologies to detect cytokines, it is highly important to mention that the amount of mRNA of a given cytokine does not necessarily reflect that of the secreted mediator. Lots of post-transcriptional events modify the nature as well as the amount of mediators released in the end. The high degree of complexity in these signalling networks is matched at EDI GmbH by using multiplexed protein bioarray tests in many instances.
And finally, it has to be kept in mind that a whole range of mediators cannot be detected on the RNA level (histamine, lipid mediators, reactive oxygen products, ATP, peptide hormones released from pre-formed precursors, etc.).
Therefore, whole-blood cultures, combined with a thorough selection of endpoint measurement systems represent the best available tools for an optimized substance profiling.