Meta-analysis of Natural Killer (NK) cell cytotoxicity in Myalgic Encephalomyelitis / Chronic Fatigue Syndrome (ME/CFS), 2024, Baraniuk et al

Reduced Natural Killer (NK) cell cytotoxicity is the most consistent immune finding in Myalgic Encephalomyelitis / Chronic Fatigue Syndrome (ME/CFS). Meta-analysis of the published literature determined the effect size of the decrement in ME/CFS. Databases were screened for papers comparing NK cell cytotoxicity in ME/CFS and healthy controls. Twenty-eight papers and 55 effector : target cell ratio (E:T) data points were collected. Cytotoxicity in ME/CFS was significantly reduced to about half of healthy control levels, with an overall Hedges' g of 0.96 [0.75 to 1.18]. Heterogeneity was high but was explained by the range of E:T ratios, different methods and potential outliers. The outcomes confirm reproducible NK cell dysfunction in ME/CFS and will guide studies using the NK cell model system for pathomechanistic investigations.

Front Immunol (September 2024) | Link

 

Curious to see Baraniuk publishing with Marshall-Gradisnik.

 

Pleased to hear this stands up because it's one of those things where I wasn't sure if it was folklore. I've heard it repeated a lot but also seen it questioned in these pages.
A solid finding is a relief.

 

Just to clarify, is this a replication of the Australian studies from Griffith Uni we were discussing/criticising a few weeks back for having no replication attempts? Becuase if so thats big.

 

I doubt it is a solid finding as there has been several studies that could not find a difference with controls. It's mostly this Australian group (and earlier the one by Nancy Klimas in Florida) that has been pushing this narrative.

Eaton-Fitch and Marshall-Gradisnik already did a review on this in 2019, discussed here:
A systematic review of natural killer cells profile and cytotoxic function in ME/CFS. Eaton-Fitch et al. 2019 | Science for ME (s4me.info)

The MCAM study of 174 patients found no significant difference:
Natural killer cytotoxicity in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS): a multi-site clinical assessment of ME/CFS (MCAM) sub-study | Journal of Translational Medicine | Full Text (biomedcentral.com)

 

I think perhaps this should be:Heterogeneity was high but might be explained by the range of E:T ratios, different methods and potential outliers. The whole problem with NK assays is that nobody actually knows what results with any of the methods means much, other than complete failure of function in rare deficiency syndromes.

Otherwise the abstract doesn't tell us anything new.

I may be hallucinating but my memory is that at an IiME meeting James Baraniuk made a comment about Nancy Klimas's NK work that 'she can't even reproduce her own data'.

I think if we want confirmation of the solidity of the NK claim it needs to come from somewhere other than the Klimas/Gradisnik stable.

 

I once consulted with a MD at a local university teaching hospital here in the USA who spent his whole career (he was close to retirement) working in the innate immune system realm because I had a couple anomalous immune system blood test results that were consistently appearing, of which one of them was a Natural Killer (NK) cell cytotoxicity assay. His take was just like Jonathan's. He said in his experience he didn’t trust any of the commercial lab results and only one university lab did he think that it was useful to use their results. He also said that he never relied on one result for NK cells and got multiple results from that Lab before he started making evaluations.

 

Full article now available at Link | PDF

 

Effect sizes for the studies:


They looked at 28 total studies. There are multiple per study in the chart because they were stratified by E:T ratio.

What they said about Mawle et al:

Adjusting for publication bias gave effect size of 0.75 (95% CI, 0.67–0.83):

 

Also, Mawle et al, one of the few negative results, used 1988 Holmes criteria, which does not require PEM.

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The full text says it a little less confidently:

 

This meta-analysis excluded the MCAM study for the following reason:

The chart of studies certainly looks like something real to me, assuming their reasons for excluding papers were sound.

 

Oh, only 2 out of 28 of the studies used ICC, one of which had a small effect size. The rest used Fukuda or Holmes. (Reference 3 is the paper about ICC.)

Still, might give insight into whatever Fukuda is measuring.

 

12 out of the 28 studies in the review came from the same research team as the reviewers at Griffith University. There are also 4 from the Klimas group in Florida who previously advocated this line of research. Other studies are rather old, from before 2000.

 

It also seems that the authors have included multiple estimates from the same study (for example different E:T ratios). I don't think their modelling accounts from the correlation between these, so it is similar to counting some studies multiple times.

 

The MCAM did test their methods first to check if it correlated with the gold standard of chromium-51 release tested on whole blood on the same day.
https://pubmed.ncbi.nlm.nih.gov/33819446/