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Antigenicity of glutamyl polypeptides has been the subject of many studies. Early interest arose from the fact that these peptides were one of the components of the capsule of Anthrax Bacillus and of Subtilis-Mesentericus group of organisms ( 1,2). Another more recent source of interest in antigenicity of these glutamyl peptides is the fact that polymers of them have been shown to have promise as plasma volume expanders (3). Interest has centered both on polymerized glutamyl peptides synthesized from straight chain peptide obtained from culture filtrates of B . mesentericus and on synthetic glutamyl peptides. The antigenicity of synthetic peptides has been studied by Stahman(4) and by Maurer ( 5 ) with somewhat discrepant results. This report presents data on antigenicity in humans of a branched chain glutamyl polymer which by actual test had molecular dimensions required for a satisfactory plasma volume expander in humans. As the question of antigenicity in humans of an otherwise suitable expander is of critical significance the findings are of considerable interest but must be confirmed by further studies.Materials and methods. The glutamyl peptide polymer was prepared by previously described methods (3,6). The backbone and side chains were gamma linked peptides obtained from B . mesentericus culture filtrates. The molecular weight was approximately 80,-000 by light scattering methods. The half life in blood stream of humans was approximately 15 hours. The material was essentially free of polysaccharide by the anthrone test, showing less than 2 pg of color-producing materia1/200 mg of peptide. It was dissolved as polysodium salt in isotonic saline to give a 2.5% solution. Immunization procedure in 24 human volunteers was essentially the same as that of Kabat and Berg (7) in testing mtigenicity of dextran preparations. After preimmunization bleeding, subjects were skin tested on one forearm with intracutaneous injection of 5'0 pg of polymer, and with a saline control on the other forearm. Skin tests were read in 20 minutes, 24 hours and 72 hours. After the 72-hour reading 2.5 mg of polymer in saline solution was injected subcutaneously. Another similar strength immunizing dose was given 12 days later. Two weeks later the skin test was repeated and read at the same time intervals. Then blood was taken for serological studies. Those subjects showing any evidence of reaction were skin tested again one month later. Quantitative precipitin tests were performed by the method of Heidelberger and McPherson (8) using the Folin-Ciocalteu tyrosine reagent as described by Kabat(9). Sera were kept in refrigerator for 2 weeks to remove complement. Three ml aliquots of pre-and postimmunization sera were mixed in 15 ml conical bottom centrifuge tubes with varying amounts of polymer (Table 11) and incubated at 37°C for 1 hour. They were then kept in refrigerator for 1 week with mixing twice a day. Any precipitate was collected by cold centrifugation and washed twice with cold saline prior to analysis. Complement fixation test ...

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Experiments on the inhibiting effect of hunian and sheep red blood cell extracts on the hemagglutinating action of mumps and influenza viruses have been described in a previous report (1). Results were presented which suggested that the inhibiting agent found in these red cell extracts was a derivative of, or identical with, the material which in the intact cell constitutes the receptor site for the virus in the hemagglutination reaction. These results consisted partly in a demonstration that, in the systems studied, the species specificity of the inhibition reaction paralleled that of the hemagglutination reaction. Thus it is known that influenza (PR8) virus will agglutinate human and chicken red cells, but not sheep cells; and that mumps virus will agglutinate all three types of red cells. It was found that the human red cell extracts inhibited the agglutination of human and chicken cells by influenza virus; and that of human, chicken, and sheep red cells by mumps virus. Extracts of sheep ceils, however, inhibited the agglutination of sheep cells by mumps virus, but did not inhibit agglutination of human and chicken cells by influenza virus. Further support for the view above mentioned was provided by the discovery that in a mixture of virus and inhibitor at 37°C. the latter was inactivated, just as is the receptor of intact cells under similar conditions in the elution phenomenon described by Hirst (2).Recently three other laboratories have reported interesting data in relation to the effect of various tissue and cell extracts and other substances on virus hemagglutination and multiplication. Friedewald, Miller, and Whafley (3) described the hemagglutination-inhibiting effects of saline extracts of various human and animal tissues and red cells. HorsfaU and McCarty (4) produced evidence to show that certain bacterial and plant polysaccharides seem capable of interrupting the multiplication of PVM virus in mouse lung. The intrapulmonary multiplication of virus was reflected by a rise in hemagglutination titer of triturated infected mouse lung. Administration of the polysaccharides diminished or prevented this increase in titer after infection. Green and Woolley (5) have demonstrated the inhibitory effect of various animal and * Aided by a grant from the National Foundation for Infantile Paralysis.