The key to understanding autoimmune diseases like rheumatoid arthritis and lupus may have been hiding in our genes all along—and two scientists found it.
In January 1972, a scientific paper appeared in the journal Science that would forever change our understanding of how our genes influence our susceptibility to disease. Baruj Benacerraf and Hugh McDevitt proposed a revolutionary idea: that our immune responses are genetically controlled by genes within the major histocompatibility complex (MHC), known in humans as the Human Leukocyte Antigen (HLA) system 1 .
Their insight created an entirely new field of research, earned Benacerraf a Nobel Prize (though many colleagues felt McDevitt was unjustly overlooked) 2 , and laid the foundation for fifty years of investigation into the genetic underpinnings of autoimmune diseases like rheumatoid arthritis, systemic lupus erythematosus, and ankylosing spondylitis 1 2 .
Before this discovery, scientists struggled to explain why some people developed autoimmune diseases while others didn't. Families often had multiple affected members, suggesting a genetic component.
The MHC was already known for its role in organ transplant rejection, but Benacerraf and McDevitt revealed its function as a master controller of immune responses.
Born in Caracas to a Sephardic Jewish family, Benacerraf spent part of his childhood in Paris before his family returned to Venezuela in 1939, narrowly avoiding the Nazi occupation of France 2 .
He was accepted to only one medical school, the Medical College of Virginia, likely due to his foreign birth and Jewish heritage—significant obstacles in that era 2 .
McDevitt grew up in Wyoming, Ohio, just outside Cincinnati. His father was a general surgeon who began taking him on morning rounds beginning in third grade 2 .
His father shared medical stories including one about Paul Ehrlich, who won the Nobel in 1908 for his "side chain theory"—a forerunner of McDevitt's work on antigen presentation 2 .
Benacerraf, along with colleagues Bill Paul and Ira Green, began by working with guinea pigs, showing that immune responses to simple antigens were under clear genetic control 2 .
McDevitt and his collaborators identified the precise location of immune response genes within the major histocompatibility complex through meticulous breeding experiments in mice 2 .
About fifteen months after their paper was published, two independent research teams discovered that the HLA antigen known as HLA-B27 profoundly affected susceptibility to ankylosing spondylitis 2 . This represented the first clear evidence that genetic variations in the MHC could dramatically influence disease risk.
| Disease | HLA Variant | Increased Risk | Year Identified |
|---|---|---|---|
| Ankylosing Spondylitis | HLA-B27 | Substantial (Over 90% of patients carry this marker) | 1973 |
| Celiac Disease | HLA-DQ2.5 | Very High | Late 1970s |
| Rheumatoid Arthritis | HLA-DRB1 shared epitope | Significant | Late 1970s |
| Type 1 Diabetes | HLA-DQ8 | Moderate to High | 1970s-1980s |
The connection between HLA-B27 and ankylosing spondylitis was the first clear evidence that genetic variations in the MHC could dramatically influence disease risk, exactly as Benacerraf and McDevitt had predicted 2 .
One of the most clinically valuable applications of HLA research has been in understanding severe adverse drug reactions.
Fifty years after the original paper, one of the most exciting new hypotheses is that HLA molecules may influence disease susceptibility by shaping our gut microbiome 2 .
Research has shown that the MHC does affect the intestinal microbiome in both rodent models and humans 2 . Healthy individuals with HLA alleles like HLA-B27 have detectably different gut bacteria compared to those without these alleles, even before any disease develops 2 .
HLA binding groove structure determines which antigens can be presented to immune cells.
Example: Celiac disease: HLA-DQ2.5 presents gluten peptides differently than HLA-DQ2.2
Foreign antigens resemble self-antigens, leading to accidental autoimmunity.
Example: Rheumatic fever: Streptococcal proteins mimic heart tissue
Certain HLA proteins misfold, triggering cellular stress responses.
Example: Spondyloarthritis: HLA-B27 misfolding may activate unfolded protein response 2
HLA type shapes which gut bacteria thrive, influencing immune development.
Example: Multiple diseases: HLA-B27 carriers have different gut bacteria composition 2
Fifty years after Benacerraf and McDevitt's landmark paper, their fundamental insight has been overwhelmingly validated. However, many mysteries remain, and some have deepened with further investigation.
As researchers noted in a 2022 anniversary reflection, "there remains a dearth of evidence that the human MHC controls the immune response to a self-antigen" 2 . Despite strong statistical associations between specific HLA types and autoimmune diseases, scientists have struggled to prove that the predisposing HLA allele directly causes an immune response to a particular self-antigen.
| Research Tool | Function/Application | Modern Advances |
|---|---|---|
| ELISPOT Assays | Detect antigen-specific T cells | Increased sensitivity, automation |
| Tetramer Staining | Identify T cells recognizing specific HLA-peptide complexes | Multiplex tetramers for complex diseases |
| DNA Sequencing | Identify HLA gene variants | Next-generation sequencing for complete HLA typing |
| Flow Cytometry | Characterize immune cell populations | Mass cytometry (CyTOF) for 40+ parameters |
| Animal Models | Study disease mechanisms in controlled settings | Humanized mice with HLA transgenes |
| Microbiome Analysis | Profile gut bacteria composition | 16S rRNA sequencing, metagenomics |
Years of Research
Diseases Linked to HLA
HLA Variants Identified
The authors of the 2022 anniversary paper suggest that "many HLA alleles predispose to disease by virtue of their effect on the immune response to the microbiome" 2 .
This represents a subtle but important shift from the original framework—focusing not on how we respond to our own tissues, but on how we respond to the microbes that live within us.
Benacerraf and McDevitt's 1972 paper represents what the 2022 anniversary reflection calls a "paradigm shift in rheumatology" 2 . Like Watson and Crick's suggestion about DNA replication, their insight opened entire new fields of investigation 2 .
The two scientists took different paths—Benacerraf from Venezuelan-French-Jewish heritage through medical school obstacles to Nobel Prize recognition; McDevitt from childhood rounds with his surgeon father to being considered by many "seriously overlooked" by the Nobel committee 2 . Yet together, they established a fundamental principle that continues to guide research today.
Fifty years later, the question "Did Baruj Benacerraf and Hugh McDevitt get it right?" has a nuanced answer. They were profoundly correct that HLA molecules are master controllers of immune response and disease susceptibility. The specific mechanisms, however, have proven more complex than anyone could have imagined in 1972.
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