March 25, 1942

Dr. Warren Weaver

Rockefeller Foundation

49 West 49th Street

New York, New York

Dear Warren:

I submit this letter to you as a brief report on the work which my collaborators and I have been doing this year on problems of immunochemistry with the support of the grant which you made us last year, and an application for an additional sum for the coming year to speed up our work along one particular line.

During the period since July 1, 1941, work in immunochemistry has been carried on by Dr. Dan H. Campbell, Dr. David Pressman, Mr. Carol Ikeda, Mr. Stanley Swingle, and other assistants and students. A number of interesting results have been obtained, and several papers describing them have been or are being submitted for publication. One field in which a large amount of work has been done is the study of precipitation reactions between antibodies and simple chemical substances containing two or more haptenic groups. It was observed by Landsteiner and van der Scheer that certain azo dyes gave precipitates with antisera. I interpreted this observation as evidence for the framework theory of precipitates. In order to test this we prepared a large number of substances containing one or more phenylarsonic groups in the molecule. We found that all of the substances with two or more of these groups in a molecule gave precipitates with antisera made with use of azo proteins containing the phenylarsonic acid group, whereas the substances with only one group per molecule did not precipitate. Quantitative analytical data were obtained for the precipitates, giving strong support to the framework theory and also providing evidence that antibodies are bivalent. Some preliminary results of this nature were described in a publication in the Proceedings of the National Academy, and a detailed account of the work is to be published in three papers in the Journal of the American Chemical Society.

A technique has been developed whereby diazotized amines can be coupled with red blood cells without destroying the cells. Using this technique a number of investigations have been carried on to obtain information regarding the nature of the agglutination reaction. An account of some of these results is being published in the Journal of Immunology.

The most interesting results obtained are those dealing with the manufacture of antibodies in vitro. It has been found possible to convert a normal protein solution into a solution with the properties of an animal antiserum to a specific antigen. A representative experiment is that in which a solution containing 1 per cent of pneumococcus polysaccharide Type III and 1 per cent of bovine gamma globulin was heated at 57° for two weeks. At the end of this treatment the solution was found to precipitate pneumococcus Type III polysaccharide, and not Type I and VIII, and it also was found to agglutinate Type III pneumococcy and not Type I or II. A purified protein solution obtained by removing the polysaccharides was found to have the same properties of a specific antiserum to Type III pneumococcus polysaccharide.

Our results indicate that our general method may be used to prepare an antiserum in the laboratory toward antigens of varied types, including those for which animal antisera are not available. We are planning to carry on experiments using toxin, viruses, bacteria, and other antigens. An interesting possibility is the use of human globulin as the protein from which to manufacture antisera, thus eliminating the danger of serum sickness.

I think that there exists a reasonable possibility that antisera of value in the protection against and treatment of disease may be made by our technique. In order that the investigation of this possibility may be carried out without delay, I respectfully apply for an additional grant of money from your Foundation, for the period July 1, 1942 to June 30. 1943. I propose that our general program of experiment on the nature of immunological phenomena be continued with the support of the grant of $11,000.00 previously made, and that an intensive investigation of our new technique, especially with respect to its practical application, be supported by an additional grant of $20,000.00. This would cover the salaries of about three men trained in immunology or bacteriology and about three assistants, and the expense of chemicals, apparatus, and experimental animals. Although the Gates and Crellin Laboratories are becoming rather crowded because of the defense projects being carried out here, there is still room to take care of this expanded research program in immunology.

Because of the generality of the new method of making antibodies in vitro, I have some confidence that the proposed program will lead to interesting results.

Sincerely yours,

Linus Pauling

LP:jr