WORLD OF MICROBIOLOGY AND IMMUNOLOGY Ehrlich, Paul177•
EEhrlich, Paul HRLICH, PAUL(1854-1915)
German physicianPaul Ehrlich’s pioneering experiments with cells and body tis-
sue revealed the fundamental principles of the immune system
and established the legitimacy of chemotherapy—the use of
chemical drugs to treat disease. His discovery of a drug that
cured syphilissaved many lives and demonstrated the poten-
tial of systematic drug research. Ehrlich’s studies of dye reac-
tions in blood cells helped establish hematology, the scientific
field concerned with blood and blood-forming organs, as a
recognized discipline. Many of the new terms he coined as a
way to describe his innovative research, including
“chemotherapy,” are still in use. From 1877 to 1914, Ehrlich
published 232 papers and books, won numerous awards, and
received five honorary degrees. In 1908, Ehrlich received the
Nobel Prize in medicine or physiology.
Ehrlich was born on March 14, 1854, in Strehlen,
Silesia, once a part of Germany, but now a part of Poland
known as Strzelin. He was the fourth child after three sisters
in a Jewish family. His father, Ismar Ehrlich, and mother, Rosa
Weigert, were both innkeepers. As a boy, Ehrlich was influ-
enced by several relatives who studied science. His paternal
grandfather, Heimann Ehrlich, made a living as a liquor mer-
chant but kept a private laboratory and gave lectures on sci-
ence to the citizens of Strehlen. Karl Weigert, cousin of
Ehrlich’s mother, became a well-known pathologist. Ehrlich,
who was close friends with Weigert, often joined his cousin in
his lab, where he learned how to stain cells with dye in order
to see them better under the microscope. Ehrlich’s research
into the dye reactions of cells continued during his time as a
university student. He studied science and medicine at the uni-
versities of Breslau, Strasbourg, Freiburg, and Leipzig.
Although Ehrlich conducted most of his course work at
Breslau, he submitted his final dissertation to the University of
Leipzig, which awarded him a medical degree in 1878.
Ehrlich’s 1878 doctoral thesis, “Contributions to the
Theory and Practice of Histological Staining,” suggests that
even at this early stage in his career he recognized the depth of
possibility and discovery in his chosen research field. In his
experiments with many dyes, Ehrlich had learned how to
manipulate chemicals in order to obtain specific effects:
Methylene blue dye, for example, stained nerve cells without
discoloring the tissue around them. These experiments with
dye reactions formed the backbone of Ehrlich’s career and led
to two important contributions to science. First, improvements
in staining permitted scientists to examine cells, healthy or
unhealthy, and microorganisms, including those that caused
disease. Ehrlich’s work ushered in a new era of medical diag-
nosis and histology (the study of cells), which alone would
have guaranteed Ehrlich a place in scientific history.
Secondly, and more significantly from a scientific standpoint,
Ehrlich’s early experiments revealed that certain cells have an
affinity to certain dyes. To Ehrlich, it was clear that chemical
and physical reactions were taking place in the stained tissue.
He theorized that chemical reactions governed all biological
life processes. If this were true, Ehrlich reasoned, then chem-
icals could perhaps be used to heal diseased cells and to attackharmful microorganisms. Ehrlich began studying the chemical
structure of the dyes he used and postulated theories for what
chemical reactions might be taking place in the body in the
presence of dyes and other chemical agents. These efforts
would eventually lead Ehrlich to study the immune system.
Upon Ehrlich’s graduation, medical clinic director
Friedrich von Frerichs immediately offered the young scientist
a position as head physician at the Charite Hospital in Berlin.
Von Frerichs recognized that Ehrlich, with his penchant for
strong cigars and mineral water, was a unique talent, one that
should be excused from clinical work and be allowed to pur-
sue his research uninterrupted. The late nineteenth century
was a time when infectious diseases like cholera and typhoid
feverwere incurable and fatal. Syphilis, a sexually transmitted
disease caused by a then unidentified microorganism, was an
epidemic, as was tuberculosis, another disease whose cause
had yet to be named. To treat human disease, medical scien-
tists knew they needed a better understanding of harmful
microorganisms.
At the Charite Hospital, Ehrlich studied blood cells
under the microscope. Although blood cells can be found in a
perplexing multiplicity of forms, Ehrlich was with his dyes
able to begin identifying them. His systematic cataloging of
the cells laid the groundwork for what would become the field
of hematology. Ehrlich also furthered his understanding of
chemistry by meeting with professionals from the chemical
industry. These contacts gave him information about the struc-
ture and preparation of new chemicals and kept him supplied
with new dyes and chemicals.
Ehrlich’s slow and steady work with stains resulted in a
sudden and spectacular achievement. On March 24, 1882,
Ehrlich had heard Robert Koch announce to the Berlin
Physiological Society that he had identified the bacillus caus-
ing tuberculosis under the microscope. Koch’s method of
staining the bacillus for study, however, was less than ideal.
Ehrlich immediately began experimenting and was soon able
to show Koch an improved method of staining the tubercle
bacillus. The technique has since remained in use.
On April 14, 1883, Ehrlich married 19-year-old Hedwig
Pinkus in the Neustadt Synagogue. Ehrlich had met Pinkus,
the daughter of an affluent textile manufacturer of Neustadt,
while visiting relatives in Berlin. The marriage brought two
daughters. In March, 1885, von Frerichs committed suicide
and Ehrlich suddenly found himself without a mentor. Von
Frerichs’s successor as director of Charite Hospital, Karl
Gerhardt, was far less impressed with Ehrlich and forced him
to focus on clinical work rather than research. Though com-
plying, Ehrlich was highly dissatisfied with the change. Two
years later, Ehrlich resigned from the Charite Hospital, osten-
sibly because he wished to relocate to a dry climate to cure
himself of tuberculosis. The mild case of the disease, which
Ehrlich had diagnosed using his staining techniques, was
almost certainly contracted from cultures in his lab. In
September of 1888, Ehrlich and his wife embarked on an
extended journey to southern Europe and Egypt and returned
to Berlin in the spring of 1889 with Ehrlich’s health improved.
In Berlin, Ehrlich set up a small private laboratory with
financial help from his father-in-law, and in 1890, he was hon-womi_E 5/6/03 2:12 PM Page 177