Outside the lab, looking in

After quite a busy couple of weeks in the lab, I have a bit of a breathing room to think about the world outside the lab.

Outside the lab

But not too far outside…

I’ve been trying to drum up interest in the lab to enter a competition. The university is running a competition for short videos that explain our research to the public. While everyone is quite enthusiastic about the research we’re doing, they are somewhat less enthusiastic about being on camera to discuss it. As I may have mentioned (ahem, repeatedly) on this blog, I am committed to talking to the public about science. In this case, that means shedding the shyness and choosing the cleanest lab coat to wear in the video.

In the interest of not being totally awful, I went to a seminar about speaking on camera. During an exercise to get used to use talking aloud as a form of outlining, I listened to a few other academics talk about their projects. While I may not be ready for my prime time close up, it was a great reminder of what it’s like to be the lay audience for a presentation on a very specialized topic. Hopefully that will serve me well, not only in the video competition, but also in addressing you, here at this blog.

Are there any common obstacles that prevent you from truly engaging with a new, potentially difficult topic? How about any shows, books, or other media that are really getting it right, particularly when it comes to addressing a broad audience about tough scientific topics?

Who knows what happens in the nose?

Today’s topic is related to the question in the last post. Even before the innate immune system kicks in, your body is protected from marauding bugs by your epithelial surfaces. Those include your skin and the linings of your respiratory, digestive, and urinogenital tracts. Epithelial cells are big, immobile cells that are tightly connected to their neighbors, making them excellent barriers. We also refer to some of our epithelial surfaces as mucosal surfaces. Mucus is also key to today’s post.

Thus, I present to you: snot.

We typically refer to nasal mucus as snot. It’s produced by epithelial cells in the nose, and acts as a kind of fly paper to catch pathogens, allergens, and air impurities that you breathe in. When a danger signal is detected, neutrophils (a type of innate immune cell) are called to fight your infection. The neutrophils are also killed in this process, releasing iron into your mucus and turning it green.

I won’t go into anymore detail here. This information comes from the British Society for Immunology’s Secret Life of Snot, and you should check out their page for more snot facts. They’ve also got a recipe for making your own snot that doesn’t involve introducing any pathogens into your airways, and lots more information about a range of immunology topics.

The major goal of this blog is to reach out to the public to answer questions about immunology and build interest in science. In March 2014, I pursued that same goal by volunteering with the British Society for Immunology (BSI) at the Big Bang Fair. The Big Bang Fair was an outstanding opportunity to talk to school kids, teachers, and parents about science that is relevant to our everyday lives. Absolutely check out a Big Bang Fair event if it’s in your neighborhood.

Feel free to share information about any science events you’ve attended, or that may be coming up, in the comments!

Quick, quick, slow- innate and adaptive immunity

In addition to falling into myeloid and lymphoid subdivisions, immune cells can also be classified based on how they function. The cells that act quickly in an immune response, using premade defenses, are part of the innate immune system. On the other hand, cells that respond more slowly and specifically are part of the adaptive immune system.

Innate immunity

Although myeloid and lymphoid cells make up the innate immune system, I’ll focus mostly on myeloid cells like neutrophils, macrophages, and dendritic cells.

Innate immune cells typically act at the site of infection. If you eat something that contains an intestinal pathogen or stomach bug, the innate cells in your gut will launch the first attack against it. Innate cells need to act fast, so they recognize patterns that are common among pathogens rather than pieces of specific bacteria or viruses. That means your innate cells will register “bacteria that use a whip-like structure to move around” rather than “Salmonella enterica Typhimurium.” That pattern recognition results in innate cells releasing their defenses against the bacteria, which are often ready-made and stored in pockets inside the cells.

This early defense mechanism is critical for keeping the vast majority of nasty stuff in check. But sometimes you need a more sophisticated approach.

Adaptive immunity

As an example of the lymphoid cells acting in adaptive immunity, I’ll focus on T cells.

Unlike neutrophils or macrophages, T cells cannot directly recognize pathogens. They need help from other cells in order to respond to a threat. An innate cell, often a dendritic cell, will become activated at the site of infection, then travel to an organ that specializes in immune activation. It will display parts of the bacteria on its surface and present them to a lot of T cells, along with additional information that specifies “Salmonella enterica Typhimurium.” Eventually it will find a T cell that recognizes the part of the bacteria, which will then make copies of itself and tools to fight against the infection. Finally the T cells will travel to the site of infection to fight the pathogen. As you can imagine, this takes considerably longer than the innate immune response.

Innate and adaptive immunity work together to keep us healthy. Before these systems get activated, however, there’s a first line of defense that pathogens have to make it through. Can you name it?

Two flavors of immune cells: myeloid and lymphoid

The distinction between myeloid cells and lymphoid cells

We recently covered the fact that hematopoietic (blood) stem cells can make all the blood cell types in the body, including white blood (immune) cells. The immune cells are broadly broken down into two categories: myeloid and lymphoid.

 

Myeloid cells

Myeloid cells include neutrophils, macrophages, dendritic cells, mast cells, and granulocytes. These cells tend to be found in the tissues- your skin, organs, and other locations where an infection might rear its head. They have three main jobs.

1. Pick up information from their environment, which will tell them if any threats are nearby.
2. Kill infected cells and pathogens like bacteria.
3. Communicate with other immune cells, including lymphoid cells, sounding the alert when danger is detected.

Myeloid cells are part of the innate immune system.

Lymphoid cells

Lymphoid cells, or lymphocytes, include T cells, B cells, and natural killer (NK) cells. As the name suggests, these cells are prominent in the lymph, a fluid that drains from the tissues containing cells and debris. These cells tend to have a large nucleus and few granules (the pockets that contain their ammunition). Lymphocytes mount a more sophisticated, targeted attack against threats than myeloid cells. B cells and T cells are part of the adaptive immune system, while NK cells are known to have properties of innate and adaptive immune cells.

We think about myeloid and lymphoid cells separately, since they are made and live in distinct areas in the body, plus they have different jobs. But as we continue, you’ll see how closely linked they must be to keep us healthy- no immune cell is an island.

Next time we’ll talk about the key differences between the innate and adaptive immune responses. As you may guess from the names, innate immunity uses techniques that cells are “born” with to fight infections. Adaptive immunity requires adaptation. For me, that’s where things start to get really interesting!

Drop me a line in the comments if you have thoughts about which type of cells, myeloid or lymphoid, would respond first if you cut your finger.

Let’s chalk it up to cultural differences – pipetting aid

My transition to the United Kingdom has been largely smooth. No language barrier, very similar social expectations. I’ve done the requisite amount of grumbling about cars (ahem, or buses) driving on the wrong side of the road. I grouse with the best of them about rainy days and gray skies. Overall, though, I’ve been quite happy here, feeling right at home. There are a few instances, however, where the cultural differences have made themselves known. Here, then, the first in a series of anecdotes about being an American scientist in the UK,

Scientists use a lot of unfamiliar tools for doing familiar tasks. Enter: the electric pipetting aid. One of the ways that scientists measure liquids is by drawing them up into a plastic tube that is marked with precise volume measurements. In order to suck the liquid up, we use an electric pipetting aid. You hold it in your hand, fit the upper end of the plastic tube into the nozzle, place the bottom of the plastic tube into the liquid, then press a button to suck up the liquid.

The electric pipetting aid

At home, we referred to these as pipet guns.

Here, the first time I said it, my coworkers looked at me like I was a mustachioed, diminutive, cowboy hat-wearing, pistol-toting cartoon character.

Lesson learned. Now, like my coworkers, I refer to it by its trademarked name or simply as a pipettor.

The birds and the bees of immune cells

Where do immune cells come from?

Before we get into the logistics of how the cells of our immune system do their jobs, let’s talk about where they come from. You may be more familiar with the term white blood cells, which also describes immune cells. White blood cells share a common ancestor with red blood cells and platelets, the hematopoietic stem cell.

Hematopoietic stem cells

The term stem cell has become loaded with political baggage recently, but has a rather simple definition. When a stem cell undergoes cell division, which is to say it splits into two cells, it makes one stem cell (self-renewal) and one cell that is more specialized or developed. Self-renewal and the ability to give rise to all the cells in a family (for instance, all blood cells) are the hallmarks of stem cells. The hematopoietic stem cell (HSC) is able to make all the cells in the hematopoietic (or blood) family. HSCs are typically found in the bone marrow, the inner core of the bones.

An overview of blood cell development

Progenitors

When HSCs divide to give rise to one HSC and one more committed cell, the more committed cell is termed a progenitor. A progenitor is not a stem cell, as it can no longer give rise to all of the blood cells. A progenitor is also not a mature immune cell, ready to do battle with an infection. It is at an intermediate phase, capable of making a variety of closely related cells, but no longer able to make more distantly related cells.

In the bone marrow, common myeloid progenitors give rise to myeloid cells, the early response team of the immune system, as well as red blood cells and platelets. Common lymphoid progenitors make lymphoid cells, including B cells, natural killer cells, and T cells. However, the bone marrow cannot make T cells. Lymphoid progenitors have to leave the bone marrow, travel through the bloodstream, and go to the thymus, an organ that specializes in making T cells.

We’ll build on these concepts and diagrams as we go. All questions welcomed in the comments!

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What is immunology?

Perhaps you already know that immunology, or the science of the immune system, is a study of the processes that keep you well and help you get better. You catch a cold because you ride the bus to work everyday and someone is always coughing on the bus. (Just, you know, hypothetically. But I’m looking at you, guy in the flat cap.). Your immune system senses the virus, fights it, then braces itself for another bus commute.

Immunology is, indeed, the study of how you stay healthy and fight infections, but that simplicity greatly underestimates the work of the immune system. Have you ever thought about what it entails for your immune system to sense and fight a virus?

The immune system must make sense of a constant stream of signals

• How does your immune system know it’s dealing with something threatening (virus) as opposed to something unfamiliar but harmless (food, air impurities)?
• How do your cells know that they’re dealing specifically with a virus instead of bacteria, fungi, or cancerous cells?
• Which of your immune (or white blood) cells are involved?
• How do your cells (tiny) find the offending pathogen (teeny tiny) in your body (relatively vast)?
• What do your immune cells do once they locate their targets?
• How do they know when to stop?

Immunology is the study of myriad cell types and several organs, which must be coordinated to protect you from a constant onslaught of nasty microbes. The immune system must determine between harmless and harmful stimuli. It must mount an appropriate response against harmful stimuli, by coordinating various cells with specialized functions. It must turn that response off in order to eliminate threats without causing too much collateral damage.

This is only the briefest introduction to what the immune system does and some of the questions that immunologists study. Hopefully it gave you some food for thought about the complexities of immunological self-defense. We’ll start to get into the science in the next post.

Stay healthy out there, bus commuters.

Some pertinent details about Your Immunology

A little bit about me

My name is Amanda. I’m an American immunologist living and working in the UK. I’ve been studying science since I was 12. I wanted to be a scientist since I extracted DNA and spooled it onto a glass rod in biology class. I’ve loved to write since primary school, but that went on a distant backburner when I went to college and focused on my biology degree. After my BSc, I completed a PhD in immunology and I’m currently doing postdoctoral research. I love science more than ever, but I’m not sure I’ll always be a researcher.

Which is to say…

I know a fair bit about immunology. I love thinking and talking about science, but I miss writing. Despite recent improvements, I think scientists fail to engage with their communities often enough or in the right way. I want to communicate with people who identify as non-scientists, but are still curious about science.

What you can expect

My area of expertise is a sliver of a piece of a slice of science- I am a T cell and thymus biologist. So, I’m going to talk about basic immunological concepts and on-going research. I want to tell you the things I think are fascinating about how your body tries to stay well and regain health after sickness or injury. I’ll also write a bit about the life of a scientist.

 

Our sliver of a piece of a slice

A few notes about the structure of the blog

Many posts will be accompanied by my illustrations. This is because scientists love schematics and diagrams. If you pick up an article written for a scientific audience, you’ll find similar (ahem, but perhaps more professional) illustrations.

Acronyms and abbreviations are an immunologist’s best friends. It’s inevitable that I’ll reference something that you’re not familiar with and I’ve failed to explain adequately. Call me out on those occasions. It’s easy to forget what a non-specialist won’t be familiar with.

Why I think you might care

Immunology answered a lot of questions about health and disease that I’ve had over the years, and I think it can do the same for many of you. I don’t think anyone should be excluded from understanding how the body or the immune system works, even if it’s been a long time since your last biology class. It won’t always be simple and straightforward to understand the concepts, but I’ll do my best to make it worthwhile. I hope you’ll read along and find some interesting, useful information.