A Bitter Sweet Nobel - Beutler, Janeway, and the Dawn of Innate Immunity
This post initially appeared on Science Blogs
Monday's announcement for the Nobel Prize in physiology or medicine should have been a happy occasion for my lab. On the one hand, it was given for early discoveries in the field of innate immunity - my field! On the other hand, it was given to a scientist that many* feel is undeserving of the honor, while at the same time sullying the legacy of my scientific great-grandfather.
Let me explain.
In the late 1980's, immunologists were riding high. Much of the experimental attention in previous decades had focused on T-cells and B-cells, the drivers of "adaptive immunity," and it seemed as if they had almost everything figured out. B-cells were known to make antibodies that could be released into the blood and fight infections all over the body. The activity of antibodies was discovered by German scientists over 100 years earlier (which is maybe why it is known by the archaic-sounding term "humoral" immunity), but it was only in the second half of the 20th century that scientists started uncovering the mechanisms behind antibody function. At the same time, the closely related T-cell was yielding its secrets to ingenious experiments. T-cells are behind "cell-mediated" immunity. Where antibodies can be released into blood and carry out their activities independent of the cells that make them, T-cells kill infected cells by sidling up next to them and giving them a kiss of death.
T-cells and B-cells are called "adaptive," because the receptors that they use to recognize pathogens are generated at random by cutting and rearranging pieces of genes and stitching them together in a random order. These receptors are therefore capable of recognizing functionally any molecule. In addition, both types of cells can learn during the course of an infection and remember what they learned, so that future infections with the same agent can be dealt with more quickly. By the late 80's immunologists thought they had a handle on how all of this worked.Charlie Janeway's Insight
In 1989, as an introduction to the Cold Spring Harbor Symposium on Immune Recognition, Charles Janeway wrote1:
I believe it is safe to state that our understanding of immunological recognition is approaching some sort of asymptote, where future experiments are obvious, technically difficult to perform, and aim to achieve ever higher degrees of precision rather than revolutionary changes in our understanding.
But Charlie was just being coy with this paragraph. The title of this paper is "Approaching the Asymptote?" And it turns out that question mark is vital to his thesis. Later on in the same paper, Janeway wrote:
I believe that ideas, especially good ideas, can so satisfy our desire to explain what we're studying that they can inhibit our ability to explore and to understand.
In the preceding decades, a group of scientists had been quietly plugging away at another, less flashy aspect of immunity. The receptors that controlled recognition for this type of immunity seemed boring next to their T-cell and B-cell counterparts; they are present from birth, don't rearrange genes and recognized a small, fixed set of microbial products. These so-called "innate" immune receptors were made by cells that are present at all times in tissues (rather than being recruited there during an infection like B-cells and T-cells) and it was widely believed that these cells' only job was to hold an infection at bay while waiting for B-cells and T-cells to show up and dominate the show.
But T-cell and B-cell immunologists had what Janeway called their "dirty little secret." T-cells and B-cells could recognize any protein, but they can't mount an immune response on their own. Injection of purified proteins doesn't lead to immunity, or activation of T-cells and B-cells. Janeway:
In order to obtain readily detectable responses to these [proteins], they must be incorporated into a remarkable mixture termed complete Freund's adjuvant, heavily laced with killed Mycobacteriam tuberculosis organisms or precipitated in alum and mixed with dead Bordetella pertussis organisms
These special additions are called "adjuvants," and they are absolutely necessary to get immune activation with pure proteins.
Why do we need to use adjuvants? To be quite honest, the answer is not known.
But Janeway had a theory. In the preceding years, scientists had discovered that in addition to the signal T-cells and B-cells received through their main receptors, they required a second signal, or "co-stimulation." Other researchers had independently shown that certain microbial products like LPS, a component of bacterial cell walls, had strong adjuvent activities. Janeway's insight was that the 2nd signal for T-cell and B-cell activation was linked to recognition of particular molecular patterns associated with infection.
I contend that the immune system has evolved specificalty to recognize and respond to infectious microorganisms, and that this involves recognition not only of specific [proteins], but also of certain characteristics or patterns common on infectious agents but absent from the host[...] By ignoring the importance of this microbial component of immunological recognition, I contend that we have collectively ignored a critical feature of self/nonself discrimination, the requirement for a microbially induced second signal[...] Indeed, I believe that if we fail to incorporate such ideas into our thinking, we shall fail to understand immune recognition at its most fundamental level, that is, the discrimination of self from nonself, and in the defense of the host against infection.
It would take almost 10 years to validate Janeway's prediction. In 1996, Jules Hoffman and colleagues published the paper2 for which Hoffman received the Nobel, showing that a receptor called "Toll" was essential for fruit flies to mount an immune response against fungus. At the same time, Janeway and his post-doc, Ruslan Medzhitov, were investigating a protein they were calling "human Toll" (now known as Toll-like receptor 4 or TLR4), and had shown that when cells expressed a version of the receptor that was always active, it turned on a pathway known to be important in immunity. Galvanized by Hoffman's discovery3, Medzhitov and Janeway published a paper4 in 1997 showing that this human toll also turned on proteins known to be involved in co-stimulating T-cells and B-cells.
Medzhitov and Janeway didn't know the natural activator of human Toll, but based on their evidence and the known immune function of the fly toll, they hypothesized that it was involved in the innate recognition of microbial products, and would lead to co-stimulation for the adaptive immune system. After that, the discoveries came fast. In September of 1998, Paul Godowsky and colleagues showed5 that TLR2 responded directly to microbial products, and in December of the same year, Bruce Beutler published his Nobel paper6, showing that TLR4 was the receptor for LPS.
The 2011 Nobel Prize for physiology or medicine was awarded to Ralph Steinman, Bruce Beutler and Jules Hoffmann. According to the press release:
Bruce Beutler and Jules Hoffmann discovered receptor proteins that can recognize such microorganisms and activate innate immunity, the first step in the body's immune response.
No one denies that Jules Hoffman's discovery of the immune function of Toll in flies is significant, but Beutler's contribution is a bit more dubious. Before Beutler's paper, Medzhitov and Janeway had shown that TLR4 could activate innate immune signals that led to the activation of co-stimulation, and Godowsky had shown that a different receptor, TLR2, could recognize microbial products. Though Beutler's paper was the first to actually knock out the gene for one of these receptors and show a loss of function in the mouse, the conceptual groundwork for its importance in the immune response had already been laid.
This Nobel was awarded for
the mechanisms triggering the activation of innate immunity and mediating the communication between innate and adaptive immunity.
This was the paradigm suggested by Janeway in 1989 and validated by discoveries in the late 90's. Beutler just found a receptor that bound to LPS. Janeway and Medzhitov were the first to establish the link to adaptive immunity, and Medzhitov and others (not Beutler) followed his initial discovery by showing the direct links to T-cell activation, B-cell activation and establishing adaptive immune responses. In fact, Beutler has recently been disavowing the idea that pattern recognition is important for adaptive responses7.
I should note here that I'm not exactly an unbiased source (though I think the publication record speaks for itself). My boss was a post-doc in Medzhitov's lab, putting him (and me) in Janeway's direct lineage. And there's no love lost between Medzhitov and Beutler. For the past decade, Beutler has been publishing review articles playing up his own contribution and down-playing that of Janeway. And the feud isn't restricted to the peer reviewed journals. The latest sortie in this rivalry occurred earlier this year, after Medzhitov gave a presentation to an audience of innate immunologists (including Beutler). At the end of his talk, Medzhitov announced that he wouldn't take questions, but wanted to comment on the fact that "someone" had changed the wikipedia entry on Charlie Janeway to read:
Janeway and coworkers did not actually demonstrate the existence of receptors for LPS or any other PAMPs. However, receptors for specific molecules made by microbes were eventually identified by other workers, notably [[Bruce Beutler]] , who discovered the LPS receptor[...]
He didn't name names, but said "there's only one person that would do this, and we all know who." And I don't think he was referring to Sarah Palin.
Janeway couldn't be awarded the Nobel, since they aren't granted posthumously. One could argue that Medzhitov shouldn't get it either, since he wasn't the principal investigator when his TLR paper was published. But his initial discovery, and his later work as an independent investigator firmly established the role of pattern recognition in the activation of adaptive immunity. In addition, Ralph Steinman (one of the other winners this year), was not the principal investigator on his key paper.
But regardless of the arguments for or against Medzhitov, giving the reward to Beutler, especially in light of the efforts he took to discredit Janeway and his contribution is a bit of a slap in the face. When the history books are written about this era in immunology, I wonder if this Nobel will help Beutler in sweeping Janeway under the rug.
*That should read "many scientists I know..." See my response to Ed Yong below.
1 Approaching the Asymptote? Evolution and revolution in immunology. [Note: It's a pain in the ass to find the full text of this - shoot me an e-mail if you're looking]
2The dorsoventral regulatory gene cassette spätzle/Toll/cactus controls the potent antifungal response in Drosophila adults.
3Approaching the Asymptote: 20 Years Later
4A human homologue of the Drosophila Toll protein signals activation of adaptive immunity.
5Toll-like receptor-2 mediates lipopolysaccharide-induced cellular signalling.
6Genetic and physical mapping of the Lps locus: identification of the toll-4 receptor as a candidate gene in the critical region.
7Adjuvant-enhanced antibody responses in the absence of toll-like receptor signaling.
Missing image: Image at http://lifeinlegacy.com/2003/0419/JanewayCharles.jpg | http://lifeinlegacy.com/2003/0419/JanewayCharles.jpg