How does your immune system work? New Ted Ed talk

For those new to it, Ted Ed is an initiative to create short animated talks for education purposes.

This latest one provides a cute intro to the immune system. Its pretty basic, but still kind of cool. And worth a look if you're currently stuck in bed.

https://www.youtube.com/watch?v=PSRJfaAYkW4

 

As a fun introduction to the basic ideas I agree this is pretty clever.

My only reservation, for those who might want to try to use it to understand specific illnesses, is that it does not give a clear idea of which compartments which event is happening in. For instance, it does not make it clear that T cells actually go out into tissues where the microbes are and do work there. B cells have no purpose in the inflamed tissues so do not normally go there. They generate antibody responses far away in spleen and lymph node. Phagocytes do not eat things in the blood much - everything is moving around too fast. They only eat things once they have got into tissues and grown arms. These might seem like details but lots of muddled theories about 'inflammation' are muddled because things are not put in the right compartment.

Still, as far as it goes this cartoon gives a pretty good summary.

 

@Jonathan Edwards, they describe helper T cells as having a role in antibody driven immunity (detecting antigens, I think it said). Is this their primary role, or do different helper T cells do different things?

 

T helper cells (CD4+) are specialised in that they recognise peptide fragments of antigens mostly derived from outside cells, that are presented to them in association with HLA-D (MHC ClassII) rather than HLA-A, B or C (Class I). CD8+ cells tend to recognise antigens formalised cells.

What the cells do once they have recognised antigen is probably almost anything, including helping B cells to make antibody, helping other T cells to make cytokines, or helping killer cells to kill with granzyme etc. There was a time when it was thought that different T helper subset stuck to different jobs (TH2 for helping B cells, TH1 for helping other T cells) but it became clear that there is no hard and fast distinction.

But I have always tended to think that your initial question is fair. The way T helper cells help B cells make antibody is very well understood and it is the one thing we have evidence that they do very well. I tend to think of it as their 'primary job'. Immune responses mediated by T cells on their own tend to be CD8+ mediated. Helper cells will help them along but exactly how that works and how essential it is much of the time is less clear to me. Things are complicated by the fact that 'classic' T cell mediated immunity of the sort seen to TB may very often be a strange aberration in response engineered by clever bacteria, not a normal protective response.

 

Thanks, @Jonathan Edwards!