Stimulated Cytokine testing: Biomarkers of Immune Status

 

 

 

Why test immune cytokines?
At NeuroScience, Inc., we always strive to raise awareness about the complex interplay of the neurological, endocrine, and immune subsystems that constitute the NEI Supersystem^TM. Because of this interconnectedness,  symptoms such as fatigue, low mood, anxiousness, or insomnia may be due to any number of contributors, not least of which is inflammation. Potential root causes of inflammation include infections, autoimmune disorders, environmental toxins, or disrupted gut microbiota. Even psychosocial stress can result in inflammation!

During inflammation, there is increased production of certain cytokines (small messenger proteins) by white blood cells and other cell types. This can impact neurological and endocrine functions in a number of ways, including the litany of symptoms described above which are sometimes collectively termed “sickness syndrome” or the “sickness response”, an adaptive state that “minimizes risk by limiting normal behavior and social interactions and forcing recuperation” (Chapman et al., 2008).

Not only are these cytokines players in the pathology of a given disorder, they are also reporters of immune imbalance. That’s where Stimulated Cytokine testing comes in.

What is Stimulated Cytokine testing?
Stimulated Cytokine testing is intended to assess whether an individual’s symptoms could be attributable to an imbalanced immune response. Our goal is to understand as best we can where to target therapeutic interventions, minimizing empiricism and guesswork in the therapeutic protocol.

In the test, white blood cells (which include many immune cells) are isolated from a sample of the patient’s blood. These cells are then placed in culture, either without stimulation (defined as baseline), or stimulated with phytohemagglutinin (PHA, a potent stimulator primarily of T cells) or lipopolysaccharide (LPS, principally a powerful stimulator of innate immune cells such as monocytes/macrophages and dendritic cells). After 24 hours, levels of cytokines are measured in the culture medium and compared to the normal range observed in asymptomatic individuals.

Why not just measure serum cytokines?
Many practitioners wonder why they should run a Stimulated Cytokine test; wouldn’t measuring serum cytokines give the same results? The answer is “not necessarily”. That’s because serum cytokine testing can have issues related to reliability and reproducibility, as summarized by de Jager et al. (2009), that are not encountered with stimulated cytokine testing. These issues pertain to sample handling and storage, as well as interference of endogenous plasma proteins.

Another thing to consider is that, unless the patient has a serious case of systemic inflammation, cytokine concentrations in the serum may be too low to detect. In contrast, stimulated cytokine testing first cultures white blood cells over a 24-hour time period, so any cytokines that are secreted in that time frame are concentrated in a small volume of culture medium. Furthermore, being able to stimulate the patient’s white blood cells with PHA and LPS provides a means to expand the dynamic range of the cytokines, while provocation is of course not possible when testing serum cytokines.

What do stimulated cytokine results tell us?
There are a few key proinflammatory cytokines, such as TNF-α and interleukin-1β, for which we know a fair amount about how they may impact the NEI Supersystem^TM. For example, IL-1β has been documented to activate the HPA axis, increase norepinephrine release in the hypothalamus, and increase metabolism of 5-hydroxytryptophan toward excitatory quinolinic acid, at the expense of serotonin.

However, at the same time it’s important to recognize that even a test that measures up to 17 cytokines, as NeuroScience, Inc.’s Stimulated Cytokines Comprehensive panel does, is far from actually being “comprehensive”, considering that over 100 cytokines have been described to date! Scientists still do not understand the precise function of many of these cytokines, and partly as a consequence, commercial detection assays do not include them (though this will certainly evolve over the coming years).

Therefore, we need to stay humble and realize that the cytokines we can test for today are unlikely to give us the whole story about what is going on in an individual. Imagine you were trying to understand someone who was speaking in a language for which you only knew 17 words! Nonetheless, if you heard the words “danger”, “help”, and “fire”, you would have a decent idea as to the meaning of the message. Similarly, perturbations in the cytokines that we are able to commercially assess are extremely useful as indicators of the patient’s immune status, or to use the more formal lingo, they are biomarkers of the immune system.

Thus ends Part 1 of my commentary on cytokine testing – In an upcoming entry, I’ll walk through a couple of Stimulated Cytokine test cases and provide some interpretative guidelines to apply in practice! Remember, in order to appropriately target interventions, we need to understand whether immune imbalances are an underlying issue.

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