Len Herzenberg (1931–2013)

Abstract

Leonard Arthur Herzenberg was born the 5th November 1931 in New York, USA. He studied Biology and Chemistry at Brooklyn College. Len did his PhD in biochemistry and immunology at the CalTech (Pasadena, CA, USA). When he finished his PhD in 1955 he moved to France for a Postdoc in the Institute Pasteur, where he worked with Jacques Monod. In 1957, he joined Harry Eagle at the National Institutes of Health (NIH), adding pyruvate to the recipe of “Eagle's medium”, and working on somatic cell genetics of cell lines. In 1959, Joshua Lederberg recruited Len to the Department of Genetics of the Stanford University (CA, USA). At that time, when somatic cell genetics were introduced into immunology, Len worked on H-2 and IgH genetics, in particular on IgH allotypes. The lack of methods to isolate rare genetic variants from cell lines was a limitation for his studies. Looking for technologies to solve this bottleneck, Len discovered that a group of engineers headed by Mack Fulwyler at Los Alamos National Laboratories (New Mexico, USA) had developed a particle sorter by combining a Coulter volume sensor with an ink jet printer device. Len asked them to add a detector for fluorescence of the particles, but they rather gave him the construction plans. Len collected the 14 000 $ required to build a prototype at the Stanford instrumentation laboratory. This prototype was presented in 1969 1, improved and in 1972, the instrument was baptized “Fluorescence-activated Cell Sorter”, also known as FACS. Soon, it turned out to be a key instrument for the analysis of the immune system. For the first time ever, FACS allowed the quantitation of expression of a particular protein in individual cells, stained with fluorescent, specific antibodies, and the isolation of individual cells according to their protein expression. Soon several proteins could be detected simultaneously, using antibodies with different fluorescent dyes. It was a breakthrough for cytometry and immunology. And although todays “flow-in-air” FACS machines incorporate all kind of devices not available in the 70's, they still operate according to the original principle. Today, the speed of sorting has increased from 2 000 cells per second to 40 000 cells per second, and the number of fluorescent parameters from 1 to 20. There is hardly no modern scientific concept in immunology that has not benefited from cytometric immunofluorescence and cell sorting. I personally, as a young scientist, was completely dependent on FACS, to isolate somatic variants of immunoglobulin expression for a molecular analysis of somatic hypermutation and antibody class switching 2. And the MACS technology was essentially developed to complement FACS too 3. The FACS technology continues to challenge engineers and immunologists alike and this is Len's heritage 4. At the beginning, two points were essential for the success of the FACS. First, Len succeeded in convincing Becton-Dickinson (BD) to commercialize the FACS technology, though initially, neither he nor BD believed that there was really a huge market for such machines 5. Second, the advent of monoclonal antibodies in 1975 was catapulting immunofluorescence into a new era. Len immediately recognized that, and in 1976 spent a sabbatical with Cesar Milstein at the MRC in Cambridge, UK. He returned then to Stanford with the new monoclonal antibody technology. The triade of immunofluorescence, cytometry and cell sorting became a unique and precious tool that we are still using today. Len himself, together with Lee, his wife of 60 years, and a host of talented young scientists, used the FACS technology from the start, to dissect the immune system. They visualized allelic exclusion, B cells as plasma cell precursors, discovered B1 cells, T-cell imbalances in diseases like HIV and isolated genetic variants of hybridoma cell lines. In short, they contributed essentially to our current understanding of the cellularity of the immune system 5. For his seminal contributions to immunology, Len was awarded with the Novartis Immunology prize and the Kyoto prize. Len's activities were not restricted to science, though. He was severely concerned about and reacting to McCarthyism, eugenics and HIV stigmas, activities he considered to be the responsibility of a scientist 6. Len Herzenberg died on the 27th of October 2013. Immunology has lost a great personality and scientist, an inspiring mentor and a dear friend to many of us!