The Age of International Serology, 1900-50

In spite of the popular appeal of the struggle of phagocytes, it was not cells but serum that set the style. The key event of this period is the discovery of the striking clinical effectiveness of diphtheria anti­toxin.

Although it was the diphtheria serum and its prob­lems that lent them much of their significance, the first of the national serum institutes was established just before the appearance of the serum. The Institut Pasteur was set up in 1888, following the national enthusiasm in France created by Pasteur’s success with rabies immunization (Delaunay 1962). The in­stitute was not, strictly speaking, a state concern, because it was independently funded, but it had na­tional status. Its opening marked the end of Pasteur’s active life; he had had a stroke the previous year, and the new institute was to be run not by Pasteur him­self, but by his successors, the Pastoriens.

From its beginning, the institute offered courses on bacteriological technique. Among the students were young bacteriologists from all over the world; many were medical officers of the French colonies, which led to the establishment of the Institute Pasteur d’Outre-Mer. The first four of these, in Saigon, Nhatrang, Algeria, and Tunis, were founded be­tween 1891 and 1894. Among them may also be men­tioned the HafEkine Institute in Bombay, founded in 1899 and led by a Pastorien, Waldemar Hafifkine. As Noel Bernard points out, the vulnerability of the whites in these new areas of colonization stimulated interest in the diseases endemic in them; the In­stitute Pasteur d’Outre-Mer concentrated on plague, cholera, and malaria - and snake bite (Bernard 1960). In Europe, needs were different: Centers that had begun by working on vaccines turned their atten­tion to the large-scale production of diphtheria anti­serum.

A similar evolution took place in London, leading to the foundation of the British Institute of Preven­tive Medicine, renamed the Lister Institute in 1891 (Chick, Hume, and Macfarlane 1971). Rabies at that time was an uncommon, but fatal result of animal bites in England, as on the Continent; no one could predict which bite might be fatal. Pasteur himself suggested a Pastorien, Marc-Armand Rufifer, who had connections in England and Germany, as well as Paris, to head it. In 1893 Ruffer reported on the astonishing effectiveness of Behring’s diphtheria se­rum, and in 1894 a serum department was created at the Lister. Soon after, the Wellcome Laboratories were founded to make the serum commercially.

In the same year Carl Salomonsen, director of the University Bacteriology Laboratory in Copenhagen, went to Paris to learn the techniques. On Salomon- sen’s return, he applied to his government for funding for a laboratory for Serotherapeutic experiments and undertook at the same time to produce diphtheria serum in quantity for free distribution. The Statens Serum Institutet under Thorwald Madsen became independent of the University in 1901 (Salomonsen 1902). Elsewhere too, rabies vaccination led the way to the manufacture of diphtheria serum, which was not only a tremendous therapeutic success, but a com­mercial success as well (Defries 1968).

The most important of the problems raised by the clinical use of the serum was that of standardization. The first attempt at a biological assay was made by Behring. His method was to standardize the anti­serum against the toxin. The minimum fatal dose of toxin was first established, and one unit of antitoxin was defined as the amount necessary to protect a guinea pig against IOO fatal doses of toxin. The method seemed logical, but in practice the results were unreliable.

The problem was taken up by Paul Ehrlich, head of the newly established Institut fur Serumprufung und Serumforschung in Berlin.

Ehrlich interpreted this in terms of his side-chain theory as meaning that there were two different side chains on the toxin molecule, which he called the toxophore and the haptophore groups, responsible for the toxic property and the property of neutraliz­ing antitoxin, respectively. The toxophore group, he thought, was labile, so that toxicity declined over time. A further difficulty lay in the fact that succes­sive additions of antiserum had unequal effects on the toxicity: The first few additions might not dimin­ish the toxicity at all, though antibody was being absorbed. Ehrlich thought this meant that the toxin consisted of a mixture of different components, each giving a different ratio of antigen to antibody.

The most “avid” components took up the highest proportion of antibody and took it first; the less avid, later. He illustrated this by a stepped diagram, the profile of which represented the relationship between toxicity and avidity for antiserum at each stage of neutralization. Each step represented a separate, named component, which he called toxin, toxone, and toxoid, each with named subdivisions (Ehrlich 1887­8). The development of a clearly visualized, but quite speculative chemistry, along with a new vocabulary to describe the visualized substances, was very typi­cal of Ehrlich’s thinking (Mazumdar 1976). It was the first statement of his side-chain theory, the theory of immunity around which argument raged for the next 20 years and which has never quite disappeared from immunology.

The feature of Ehrlich’s assay procedure that made it so successful was his insistence on measur­ing all new serum samples against a standard se­rum. The standard was preserved desiccated, frozen, and under vacuum, at Ehrlich’s own new specialized laboratory in Frankfurt, which continued to provide for international standardization up to World War I. Dxiring the war, communications with Frankfurt were cut off, and standards began to drift.

The decision to take over the regulation of serum standards was made by the League of Nations Health Committee in 1921. A series OfInternational Conferences on the Standardization of Sera and Sero­logical Tests was held; it was decided to keep the Ehrlich unit as the international standard, but since Germany was excluded from the League of Nations, the standard serum was to be in Copenhagen. Madsen suggested that similar agreements could be reached for other biologicals, such as hormone prepa­rations and plant extracts. In 1924, the Permanent Commission on Biological Standardization was set up with Madsen as its chairman (Hartley 1945). Copenhagen became the center of coordination for all work on serum standards, with individual sam­ples of diphtheria antitoxin and other antibacterial sera kept at Cophenhagen, Frankfurt, Hampstead, and Toronto, and at Paris at the Institut Pasteur (Jensen 1936).