1919 Nobel Prize in Physiology or Medicine — Jules Bordet

What You Will Learn

Understand how the discovery that the immune system is composed of two layers, not just one, led to advancements in the diagnosis of syphilis, antibody testing, and the identification of the bacterium responsible for whooping cough.

Antibodies Were Not Killers

Since the time of Behring and Koch, people believed that antibodies kill pathogens. If there was an antibody, the pathogen died; if there wasn't, it lived — this was the core concept of the first generation of immunology.

Bordet showed that there was a problem with this idea. His crucial experiment was as follows: when antibodies and bacteria were mixed in a test tube, the bacteria died. However, when the serum containing the antibodies was boiled and then cooled, the antibodies still recognized the bacteria, but they did not kill it.

What did this observation mean? It meant that there was something else in the serum besides the antibodies, and that this other factor was responsible for the actual killing, and it was destroyed by heat.

Bordet named this heat-labile component alexine. Today, we call it complement. The name was a perfect metaphor — a component that "complements" the antibody. It cannot kill pathogens on its own, but when combined with antibodies, it becomes a decisive killing tool.

The Landscape of the Time — Belgium, the Year After the Armistice

1919 was the year Belgium was rebuilding from the ruins. During the four years of World War I, Belgium was under German occupation, and much of the country became a battleground for trench warfare and chemical warfare. Ypres, near Brussels, where his Pasteur Institute was located, was one of the most devastated cities in Europe.

Bordet spent most of the war years in Brussels under German occupation. Research was severely restricted, experimental materials were scarce, and communication with international colleagues was virtually cut off. Nevertheless, he maintained his laboratory and, after the armistice, became one of the first Belgian scientists to reconnect with the international scientific community.

His 1919 Nobel Prize had political significance in this context. It was a symbolic event, recognizing the scientific achievements of Belgium, which had been trampled upon by Germany for four years.

At this time, all of Europe was in the midst of negotiating the Treaty of Versailles (June 28) and designing the League of Nations (early 1920). After four years of bloodshed, people were determined to create a system of international cooperation to ensure that "this would never happen again." This optimism was shattered by World War II twenty years later, but the spirit of international cooperation in this period became the foundation for future international scientific cooperation.

In the context of Korean history, 1919 is the year of the March 1st Movement. On March 1st, demonstrations for Korean independence broke out in Seoul and across the country. This movement was part of an effort to send the voice of Korea to the Paris Peace Conference. While international cooperation was being discussed in Europe after the armistice, Koreans were also trying to find their place in that international order. The results were harsh, but the legacy of this effort became the foundation for the Provisional Government and the independence movement.

Biographical Narrative — Director of the Pasteur Institute in Belgium

Bordet was born in Soignes, Belgium, in 1870. After studying medicine at the University of Brussels, he was a precocious talent, receiving the Prix Michon at the age of 19. At the age of 21, he went to Paris and worked under Metchnikoff at the Pasteur Institute.

Metchnikoff was a strong advocate for cellular immunity (phagocytosis), while Ehrlich and Behring led the humoral immunity (antibody) camp. The two camps were engaged in a fierce debate. Interestingly, instead of siding with one of the camps, Bordet took a different path: he demonstrated in the laboratory that both perspectives were partially correct.

At the age of 25, he had already published experimental results distinguishing between the two components in serum — antibodies, which are heat-stable, and alexine, which is heat-labile. This discovery defined his career.

In 1901, the Belgian government entrusted him with the task of establishing the Brussels Pasteur Institute. He led this institute for more than 30 years, becoming the father of Belgian microbiology and immunology. The Nobel Prize was awarded for his overall achievements in Brussels, not in Paris.

He was known for his meticulous and honest observational skills. He never published his experimental results unless they were clear, and he thoroughly verified the results of others when citing them. This scientific integrity was the reason why his in vitro experiments were so decisive.

Key Achievements — Separation of Recognition and Execution

Two-Layer System: Antibodies + Complement

The immune system, as visualized by Bordet, has the following structure:

1. Antibodies (Recognizers) — Recognize and bind to surface molecules of specific pathogens. Heat-stable. Highly specific.
2. Complement (Effectors) — Destroys targets to which antibodies are bound. Heat-labile. Low specificity and general.

This is the basic structure of immunology that we know today. A CS analogy fits naturally here. This is an architecture that separates recognition from execution. In software, we often design rule engines in this way:

• Rules — Recognition conditions such as "if the IP is X" or "if the message contains Y".
• Actions — Processing to be executed when a rule matches (blocking, logging, alerting).

The power of this separation is scalability. Rules can be created indefinitely, while actions can be maintained with a small number of standard processes. The immune system works in exactly the same way: antibodies are specific to each pathogen, but complement processes everything in a single standard pipeline.

However, this analogy breaks down here. Software rule engines are deterministic, but the complement system is a biochemical reaction with a cascade amplification. The first activation activates the next component, which activates the next component... This cascade amplifies a single antibody-antigen binding into thousands of destructive complexes. This is a rule engine with built-in non-linear amplification — a type of architecture not found in software.

Complement Fixation Test: Recognizing the System as a Diagnostic Tool

Bordet's discovery immediately led to a powerful diagnostic tool. The principle is sophisticated and beautiful:

1. Obtain serum from the patient's blood and heat-treat it to destroy the complement.
2. Add the antigen to be tested (e.g., a component of the syphilis bacteria) and fresh complement to this serum.
3. If the patient has syphilis, the serum contains antibodies against the syphilis bacteria → antibody-antigen binding → complement is consumed.
4. Add red blood cells (sheep, goat, or ram) and antibodies against them as indicators → If complement remains, the red blood cells are destroyed (hemolysis).
5. Result Interpretation: No hemolysis indicates that the patient has syphilis antibodies (positive), and hemolysis indicates that they do not (negative).

Even from today's perspective, this test is remarkably sophisticated. It is a way of extracting the desired information indirectly through an indirect signal — a similar approach to log-based debugging or side-channel analysis in software. We cannot directly see what we want (the presence of syphilis antibodies), so we measure the residual amount of the resource it consumes (complement).

This test was popularized as the Wassermann test and became the standard method for diagnosing syphilis for much of the 20th century. It is now used as a basis for the diagnosis of various infectious diseases and autoimmune diseases.

Bordetella pertussis: Discovery of Whooping Cough

Bordet's second Nobel-level achievement was the isolation of Bordetella pertussis. In 1906, he isolated the bacteria from Belgian girls and established a method for culturing it. Today, this bacterium is named Bordetella pertussis in his honor.

This discovery was clinically decisive. Until then, whooping cough was a childhood infectious disease that was difficult to diagnose. After the causative agent was isolated, diagnosis became possible, and this led to the development of a whooping cough vaccine (early form in 1914). The "P" in the DTaP vaccine that our children receive today is the vaccine against the bacteria discovered by Bordet.

Why Is It Important?

Bordet's Nobel Prize established the recognition that "the immune system is not a single system but a cooperative system of multiple layers." Without this recognition, it would be impossible to understand the multi-layered structure of T cells, B cells, natural killer cells, antigen-presenting cells, and cytokines that we know today.

More broadly, it established the methodology of "accurate diagnosis through indirect measurement." The complement fixation test showed a way to understand something by looking at the traces it leaves behind when we cannot directly see what we want. All quantitative immunoassays today, such as ELISA, RIA, and Western blotting, trace their lineage from here.

And his name, Bordetella pertussis, is an interesting legacy. Whooping cough is now controlled by vaccines, but the name of the person who discovered and cultured it remains as the scientific name of the bacteria, more than 100 years later. This is a representative example of how an individual's name can be perpetuated in science.

There is a lesson for us: "Design an experiment that can integrate both perspectives, showing that they are partially correct, in the debate between the two camps." In Bordet's time, Metchnikoff (cellular) and Ehrlich (humoral) were engaged in a fierce debate. Most scientists took sides and tried to refute the other side. Bordet took a different approach — he created an experiment that could integrate both perspectives. This integrative approach was the source of his discovery.

Even as you read this sentence, somewhere in the world, an infant is receiving the DTaP vaccine. The "P" component of that vaccine is the immune primer against the bacterium that a microbiologist in Brussels isolated from the throats of girls 100 years ago.

Summary of the Two-Layer Antibody-Complement System and CFT Diagnosis: Antibodies are recognizers, complement is effectors. This separation is used to measure the presence of antibodies indirectly by exploiting the characteristic that complement is consumed when antigen and antibody bind. The discovery of Bordetella pertussis opened a separate track for the diagnosis and vaccination of childhood infectious diseases.

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