Could anyone beokind and give a quick tutorial on t-cell immunity?

[meditrina]

Or if that's a bit much to ask on a fine Sunday morning, is there a good Intro to the subject I couid read?

I've just seen on another thread some discussion of how many people have had absolutely classic symptoms (and in one case a positive swab) but are testing negative for antibodies.

This could mean that any immune response they have formed was fleeting/poor. Or, as one post mentioned, involves T cells . What does that mean? Can it be tested for? And is that why one treatment they are evaluating involves blood cancer drugs which act on T cells (as well as other things) ?

(And is it likely to be connected to something I read years ago but don't properly remember about 'hidden' immunity?)

Medcram, John Campbell and Mike Hanson are good on medical/covid topics on youtube. Have a search through their past videos. JC is most accessible for a mass audience as he does nurse teaching, Medcram is much more technical, it’s still engaging to watch even though some of it goes over my head. I found this good immunity video in my watch history:

Thank you, I'll have a watch this afternoon

Is there a particular bit in those for how T-cell immunity works?

Is it known in other diseases - I could search for them too