“What’s your favourite immune cell, and why is it the T cell?”

Last weekend, I ran an IamA on Reddit where I welcomed questions from the community around immunology. I posted that after the session, I’d pick one lucky winner’s question to illustrate here!

The most upvoted question was, “What’s your favorite immune cell, and why is it the T cell?” Which is pretty funny to me because for some reason, the T cell is kind of a celebrity cell.

So this post is about why T cells are awesome.

T cells have an arm/hand (“receptor”) that goes around scanning for invaders that other cells are showing off. There are several types of T cells, and we’ll talk about three of the major players here. Even within these three subtypes, you have hundreds of thousands of T cells with different “T cell receptors” that give you coverage against virtually any invader that could strike. This is why they are called “adaptive.”

Helper T Cells


Helper T cells scan for invaders that “Professional Antigen Presenting Cells” (like B cells, Macrophage, and Dendritic cells) are showing off. When they detect an invader, they release messengers called “cytokines” that signal for other cells to come help. These cytokines also help the other cells get activated.

Cytotoxic T Cell


Cytotoxic T cells also scan for invaders, but they can see invaders that *any nucleated cell* (pretty much any cell) is showing off. They’re not limited to interacting only with the Professionals. When they detect a cancer cell or virus-infected cell, they release toxic pellets that poke holes in that cell and destroy it, preventing the virus from using that cell to make copies of itself.

3. Regulatory T Cells


Regulatory T cells tell the other cells when the job is done and it’s time to wind up. They send out a “stop” signal to the other immune cells. Researchers are exploring how to use this to help patients that have diseases where their immune cells are too active (autoimmune diseases), and are exploring how to turn these cells off in cancer patients where we want the immune response to be more profound.

These are just some of the basic functions of the three major classes of T cells. Part of why the Reddit poster’s question was funny is that it seems like every year, a new sub-type of T cell is discovered. In my response, I also alluded to my graduate research where I discovered a novel signaling pathway in T cells — in other words, a new way that T cells respond to signal. It was traditionally thought that T cells did not respond to these signals. We’re discovering new things about T cells every year, and they’re so versatile and effective from multiple angles. That’s why T cells are so awesome!

And as featured in my earlier posts, T cells play an important role in many approaches to make the immune system attack cancer. You can revisit this here, here, and here.

That said, there are many other awesome immune cell types, and you can read more about them in my immunology book and immune cell playing cards. We reached 50% of goal today on our campaign, and I’d love your support and help spread the word! Let’s make learning about our immune cells detailed and FUN!

Have a look at the playing cards, which feature fun facts and stats.

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