Spontaneous, persistent, T cell–dependent IFN-γ release in patients who progress to Long Covid, 2024, Krishna et al

Jonathan Edwards said:
I must have missed this study. I rather like it. Which is not surprising since I am in the process of writing a hypothesis that predicts excessive gamma interferon production probably from CD8 cells that should be demonstrable using ELISPOT. Now of course ELISPOT is just the old-fashioned form of FluoroSpot. ELISPOT picks up cell products using enzyme linked systems which are messy and difficult to overlay. My colleague Linda Wilkinson developed an overlay version which we called PhenELISPOT but ELISPOT never caught on that much because of the difficulty in measuring lots of things at once.

Around that time multichannel fluorescence was coming on line. My brother was soon to use FISH multichannel fluorescence to light up chromosomes with fluorescent tags with 21 colours if I remember rightly. I guess that the FluoroSpot people have dug up ELISPOT and done the obvious thing - to overlay signals using multichannel fluorescence. It may be an untested new-fangled device but having played with this sort of system my thought is that it is an obvious and very likely reliable approach.

The fact that soluble g-IFN levels have not shown up would be an expected part of the story. The signal is likely to be operating close up at much lower secretion levels than would give systemic rises.

The only caveat is that I was thinking of ME/CFS and this might be a signal system for ordinary post viral fatigue type LC. But the signal may be the same for both, just the regulation different.
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Wait, excessive IFN-γ means inflammation, right? (Isn't that quite a new direction for you?)

Is the idea then that excessive IFN-γ activates macrophages as part of the innate immune response?

If so, the difference between PVFS and ME/CFS might then be:

  1. The level and duration of this inflammation, and

  2. How well each patient is genetically equipped to deal with it—and where the macrophages unleash havoc?
Didn't Montoya's group, many years ago, already show that IFN-γ is elevated in ME/CFS patients and then drops again after two years or so?
 
Jonathan Edwards said:
I must have missed this study. I rather like it. Which is not surprising since I am in the process of writing a hypothesis that predicts excessive gamma interferon production probably from CD8 cells that should be demonstrable using ELISPOT.
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Is the hypothesis using data from Dr Cliff's team and their recent published paper?
Abnormal T-Cell Activation And Cytotoxic T-Cell Frequency Discriminates Symptom Severity In Myalgic Encephalomyelitis/Chronic Fatigue Syndrome,'25,Lee
Dolphin said:
We found that people with mild/moderate ME/CFS had increased expression of cytotoxic effector molecules alongside enhanced proportions of early-immunosenescence cells, determined by the CD28-CD57- phenotype.

In contrast, people with severe ME/CFS had higher proportions of activated circulating lymphocytes, determined by CD69+ and CD38+ expression, and expressed more pro-inflammatory cytokines, including IFNγ, TNF and IL-17, following stimulation in vitro.
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Also mentioned in this recent video by Dr Cliff showing IFN gamma data.
https://cureme.lshtm.ac.uk/index.php/2025/03/10/first-cure-me-webinar/
 
butter. said:
Wait, excessive IFN-γ means inflammation, right?
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wrong.

One of the major effects of IFN-gamma is to support B cell follicles. That interaction occurs without any inflammation. B cell follicles are there to generate antibody-producing plasma cells whose main job is to ensure enough antibody to mediate silent clearance of antigen using complement and CR1 every day. That prevents inflammation.
 
wigglethemouse said:
Is the hypothesis using data from Dr Cliff's team and their recent published paper?
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I don't know yet!! I sent the draft to Jackie Cliff on Sunday and she is going to see if she agrees with enough of it to get involved with supporting data! The basic idea does not depend on her findings but I get the impression it would blend with her ideas quite nicely.
 
butter. said:
Wait, excessive IFN-γ means inflammation, right? (Isn't that quite a new direction for you?)

Is the idea then that excessive IFN-γ activates macrophages as part of the innate immune response?

If so, the difference between PVFS and ME/CFS might then be:

  1. The level and duration of this inflammation, and

  2. How well each patient is genetically equipped to deal with it—and where the macrophages unleash havoc?
Didn't Montoya's group, many years ago, already show that IFN-γ is elevated in ME/CFS patients and then drops again after two years or so?
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The study that I linked in an earlier comment also shows that prolonged exposure to interferon gamma activation only causes them to release IL-6 and TNF-a for the first 24 hours, then it drops off.

The model in that paper uses newly differentiated macrophages as well, I believe. So we don’t actually know what the behavior of macrophages might be in ME/CFS with chronic interferon gamma stimulation and then, for example, a new stimulus.
 
Jonathan Edwards said:
wrong.

One of the major effects of IFN-gamma is to support B cell follicles. That interaction occurs without any inflammation. B cell follicles are there to generate antibody-producing plasma cells whose main job is to ensure enough antibody to mediate silent clearance of antigen using complement and CR1 every day. That prevents inflammation.
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What you are describing is only one of many effects of IFNg? So, while what you are describing as silent, might not be the whole story? I am certainly very interested to see how this will pan out in your paper!
 
jnmaciuch said:
The study that I linked in an earlier comment also shows that prolonged exposure to interferon gamma activation only causes them to release IL-6 and TNF-a for the first 24 hours, then it drops off.

The model in that paper uses newly differentiated macrophages as well, I believe. So we don’t actually know what the behavior of macrophages might be in ME/CFS with chronic interferon gamma stimulation and then, for example, a new stimulus.
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Very interesting, thank you!

PS: I am not certain, but I think IL6 and TNFa were also elevated in Montoya's paper?
 
butter. said:
What you are describing is only one of many effects of IFNg? So, while what you are describing as silent, might not be the whole story?
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Well, it would be the whole story for the interaction in the lymph node because there is no inflammation there. I did actually give a whole story of how that can be anti-inflammatory.

The point is the the habit of assuming that 'inflammation' is a package deal with each cytokine either increasing or decreasing it, has never been plausible. Gamma interferon contributes to inflammation in some situations but not others, so it isn't a question of being short of a whole story but being one of many different stories, surely?
 
Montoya:
Seventeen cytokines had a statistically significant upward linear trend that correlated with ME/CFS severity: CCL11 (Eotaxin-1), CXCL1 (GROα), CXCL10 (IP-10), IFN-γ, IL-4, IL-5, IL-7, IL-12p70, IL-13, IL-17F, leptin, G-CSF, GM-CSF, LIF, NGF, SCF, and TGF-α.

Not Il-6 or TNF -a.

Interesting to see the meme there in the next sentence though:
Of the 17 cytokines that correlated with severity, 13 are proinflammatory, likely contributing to many of the symptoms ...
 
Jonathan Edwards said:
Well, it would be the whole story for the interaction in the lymph node because there is no inflammation there. I did actually give a whole story of how that can be anti-inflammatory.

The point is the the habit of assuming that 'inflammation' is a package deal with each cytokine either increasing or decreasing it, has never been plausible. Gamma interferon contributes to inflammation in some situations but not others, so it isn't a question of being short of a whole story but being one of many different stories, surely?
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Missing the different stories? Then you’re surely missing the whole story. :)
 
If I’m remembering correctly, Rob Phair had evidence of a slight difference in interferon alpha levels in ME/CFS related to the itaconate shunt hypothesis. I’m not sure if they measured gamma as well.
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Some slides in this video (1h04+) from Phair's presentation re IFNα.

Also, from this small pilot study:
It can be seen that levels of TNF-α were higher in both the ME/CFS and long COVID groups, in comparison with matched sedentary healthy controls (both p<0.01). Furthermore, compared with matched sedentary healthy controls, ME/CFS patients had higher levels of IL-1β (p<0.005), IL-4 (p<0.005), IL-6 (p<0.005), IL-10 (p<0.001), and IP-10 (p<0.05). No differences among the three cohorts were found for IL-8, IL-13, MCP-1 or IFNγ.
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butter. said:
Missing the different stories? Then you’re surely missing the whole story. :)
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The different stories were the stories of other disease states. Whatever the story is for ME/CFS I don't see why it should have to involve the stories for other diseases. Would the story for an immune complex disease like RA have to include the local T cell response of psoriasis?
 
I've been trying to fathom whether the study authors collected enough data on symptoms to be able to identify a subset of PwME post-hoc and see if the finding holds up for them alone. Table S2 doesn't include PEM among 'cases where there was a single, predominant symptom at point of study recruitment' so probably they didn't, but I wonder if it would be worth contacting them to check.

It strikes me as a massive missed opportunity that LC studies don't look for PEM and analyse PEM cases separately as standard.
 
The authors say:

'At this stage, it is not clear whether IFN-γ is a mediator or a biomarker of Long Covid symptoms. For future work, it is worthwhile investigating whether patients with chronic postviral symptoms also exhibit high IFN-γ secretion, and if this is the case, then it could be a biomarker with wider utility. As both the buildup of inflammatory cytokines in the central nervous system have been proposed as a cause for Long Covid and chronic fatigue syndrome (CFS) (33, 47) and since CFS can be triggered by viral infections (43), it will be interesting to see whether IFN-γ secretion is higher in patients with CFS as well.'

Which further suggests that they didn't ask patients about PEM.

But if the finding held up for PwME, could IFN-γ be a diagnostic test? Or wouldn't it be sufficient, given that it wouldn't differentiate from non-PEM postviral illness?
 
Sasha said:
But if the finding held up for PwME, could IFN-γ be a diagnostic test? Or wouldn't it be sufficient, given that it wouldn't differentiate from non-PEM postviral illness?
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I would forget about diagnostic tests. We don't use diagnostic tests in other situations. We use a combination of clinical and laboratory findings to delineate each person's illness. If game interferon production by CD8 T cells is part of the process in ME/CFS it doesn't matter a jot how specific it is. It would be useful, however specific.
 
Jonathan Edwards said:
I would forget about diagnostic tests. We don't use diagnostic tests in other situations.
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I may not have understood the context in which you're framing this but so many PwME are disbelieved about their illness, by everyone from family members to their doctors, that a diagnostic test would be life-changing. And a diagnostic test would surely change how society as a whole views PwME. We've had a whole, 'Look, it's real! No, now look, it's really real! No, now it is!' thing going on for decades with every vaguely real-looking biological finding. A diagnostic test would be transformational, surely?
 
Jonathan Edwards said:
No, what would be transformational would be evidence of pathological physiology. It doesn't matter a bean how specific that is. As long as it includes ME/CFS. If it is shown to be the mechanism of normal viral myalgia and exhaustion all the better because everyone will then realise how real it is!!
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What do you mean by ‘how specific it is’?
 
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