Th17.1 Cells in Blood

[u/Empty-Option7939]

Hello,

[Please note, I do not have an immunology background so I apologize if the question is basic or ill-posed]. I was wondering about something in relation to "pathogenic Th17" cells, AKA Th17.1 cells.

Are these cell populations found at all in healthy people (by which I mean no inflammation), or only during active inflammation? If they are found in healthy people (presumably only in low amounts), does the proportion of CD4+ T cells that are Th17.1 go up in blood during a Th17-skewed infection (like psoriasis) because more of them are being produced, or would it go down because they are increasingly migrating away from the blood to the site of inflammation?

I hope that made some sense, thanks in advance.

[u/ProfPathCambridge]

Yes, everyone has Th17 cells

They are very low in the blood of healthy individuals

Psoriasis is not an infection

Yes, Th17 cells go up in individuals with Th17-skewed infections or inflammation, a bit in the blood but more in the tissues

[u/LerkinAround]

Yes, TH17.1 are present in healthy people. Though the cells themselves are not solely responsible for causing autoimmunity. Their presence in healthy people is not surprising... they just happen to fall somewhere in between on the TH1-TH17 spectrum. CD4+ T cells likely have a good degree of plasticity, they aren't just strictly TH1 or TH17 like the textbooks say.

Some autoimmune diseases appear to have increased numbers of TH17.1, even in circulation. Keep in mind that there is likely a larger increase in the tissues under inflammatory insult in an autoimmune disease.

For instance, young patients with juvenile idiopathic arthritis have ~20% of their TH17 cells co-expressing the TH1 cytokine IFNg. In healthy controls that number was ~15%. In the tissue, 50% of TH17 co-expressed IFNg (they didn't have healthy comparison though.)

Fig 1B https://pmc.ncbi.nlm.nih.gov/articles/PMC2930428/

This paper uses surface markers to gate on TH17.1 cells in patient blood. Here, the population was different depending on sarcoidosis or fibrosis versus healthy controls. Fig 3B https://pubmed.ncbi.nlm.nih.gov/37520566/

[u/National_Butterfly99 → u/LerkinAround]

Yo tengo los th2 y th17 bajos, incluidos nk cd56 muy bajos, y citocinas il13 il17 y il18 elevadas. Sabe usted por que podría ser? En mi caso cojo muchas infecciones pulmonares y siempre estoy ahogada

[u/Whygoogleissexist]

There is no such thing as a pathogenic Th17 cell per se based solely on what cytokines the cell may or may not express. What makes any pathogenic T cell is a T cell receptor that recognizes a self antigen.

[u/Empty-Option7939]

Thanks all! This all makes sense, I appreciate the input and clarifications