Q&A: Understanding the immune system

Dr. Scott Halperin, an associate professor of microbiology and immunology at Dalhousie University, talks about the immune system, progress that has been made in research and what lies ahead for scientists trying to understand how our bodies try to fight foreign invaders.
The microscope that Ralph Steinman used in the early 1970s to make his discovery about dendritic cells is displayed in his lab in New York. (Seth Wenig/Associated Press)

When the work of Montreal-born scientist Ralph Steinman was recognized by the Nobel Foundation, it drew attention to his medical research more than three decades ago into the intricacies of the human immune system.

Steinman discovered the dendritic cell, a key component in regulating how the body can react to foreign invaders.

Dr. Scott Halperin says Ralph Steinman's discovery regarding dendritic cells was a 'critical' step in ongoing efforts to understand how the human immune system works. (IWK Health Centre)

Dr. Scott Halperin, an associate professor of microbiology and immunology at Dalhousie University and head of infectious diseases at the IWK Grace Health Centre in Halifax, says Steinman's discovery was a "critical" step in ongoing efforts to understand how the human immune system works.

The award also highlights the length of time that can elapse between a discovery and understanding exactly what role it could ultimately play in improving people's lives.

"It's taken 30 years to get to the point now where there are very practical implications of the research that was discovered all those years ago," says Halperin.

"It takes that time to translate things from that very basic science to the practical — either preventative or therapeutic tools." spoke with Halperin about the immune system, the progress that has been made in research and what lies ahead for scientists trying to understand how our bodies try to fight off micro-organisms and pathogens.

What is the immune system?

The immune system is really what helps our body monitor what's us and what's not us … because we're swimming in a sea of micro-organisms — pathogens that can do us harm.

The immune system has to basically say when we swallow some food that may have some bacteria in it or when we come into contact with somebody who has a virus that this is a foreign invader that can do harm to our bodies.

How does the system work?

It's a very complex system. It works through a variety of methods which have helped guard against different types of potential invaders. The immune system has … cells that produce different products and those products can … directly kill invading pathogens or can signal other cells to help come fight.

Some dates in immunology history

1798: Edward Jenner shows that inoculation with cowpox could protect against smallpox .

1952: Jonas Salk announces the development of a trial vaccine for polio.

1983: Scientists discover the human immunodeficiency virus, the virus that causes AIDS.

2006: The U.S. Food and Drug Administration approves the first human papillomavirus vaccine.

A simple example: … our immune system has white blood cells [and] you get a cut, and your cut gets infected, and you see puss there. Well, the puss is those white blood cells that have been sent to defend against those invading bacteria.

There are multiple different types of cells that the immune system has. It has lymphocytes. It has neutrophils. And each of these have a different role. When we first get invaded by foreign material, a foreign organism, the body responds with what's called its innate immune system.

That system is really not specific for any given pathogen, but it's … a general response to an invader. It notices that there's an invader … And it does that through receptors. And one of the cells that is involved in that is called a dendritic cell, and that's what the Nobel Prize was awarded for.

How significant are the discoveries recognized by the 2011 Nobel Prize in Medicine for our understanding of the immune system?

All these discoveries are critical because the immune system is such an interwoven, complex cascade. It's a choreographed process and in understanding it we want to be able to understand the whole process from this innate immune system to what's called the adapted immune system and the cell that was discovered by Dr. Steinmann is that sort of pivotal transition cell.…

Where we want to go with this is to fully understand the immune system. If you could fully understand it, then you could control it and manipulate it and there are a lot of diseases that are due to overactivity of the immune system. There are diseases due to underactivity. People who have immuno-deficiencies, for example, or we treat with anti-cancer drugs which cause one to be immuno-suppressed, all the problems people get into — it's because of that immuno-deficiency.

As we understand more about the immune system, we can start changing the type of drugs we use and modifying them to just affect what we want to affect rather than having the side-effects, so ultimately down the road one would be able to design better drugs, design better vaccines. All this comes from understanding the immune system.

What are some of the biggest scientific breakthroughs we've seen in understanding the immune system?

They go back — just identifying what antibodies are is an important one because so much of it is about that, understanding what T-cells do. We've learned a lot about the immune system through HIV infection, the particular way that HIV affects different types of immune cells or different types of lymphocytes.

What do we know about the immune system now that we didn't know 50 years ago?

We've always known the immune system helps prevent against infection, and we've had vaccines…. We've had our understanding as we've developed vaccines through the 20th century that if you give an antigen you can get an antibody produced against it. And that antibody will protect against infection and that antibody stays around….

There are cells that produce that antibody and that can lead to long-term protection if somebody gets exposed to that pathogen again. That's a very simplistic one, that's what all of us who went to medical school back in the late 1970s and '80s … learned.

What we've learned since then is that the immune system has got its hands in so many more things, so that many diseases that are diseases of inflammation are due to overactivity of the immune system or the immune system reacting [when it] shouldn't, things like rheumatoid arthritis, things like Crohn's disease … lupus…

We've also learned that cancer in some aspects is a disease of loss of immune surveillance, because the cancerous process is a very common process that is going on and cells have mutations all the time and our immune system protects us against it.

What are the biggest hurdles facing scientists researching the immune system?

It's finding the mechanisms [of how the immune system works.] Whereas before we said, 'Oh, well, lymphocytes make antibodies, and T-cells kill virus-infected cells,' [now] we say, 'Well, how do they do that?' …

As we learn more about that, then we understand how the body naturally responds to an infection and how we can potentially, from a vaccine standpoint, how we can then use that to make better vaccines.

This interview has been edited and condensed.