Quantitative Use of Neufeld Reaction with Special Reference to Titration of Type II Antipneumococcic Horse Sera

The Neufeld reaction has recently been advocated1 for the diagnosis of the different types of pneumonia directly from the patient's sputum. For this purpose, he advised a monovalent antipneumococcic rabbit serum in order to avoid the non-specific reactions which he obtained with the use of antipneumococcic horse serum. More recently, Cooper and Walter2 reported this same “swelling” phenomenon when antipneumococcic serum from rabbits was mixed with the homologous pure culture grown in artificial media. This observation led us to examine different samples of antipneumococcic serum by mixing them with specific pure cultures and observing the degree of capsular swelling which resulted. It was found that a serum high in mouse protective units caused much more swelling than a serum low in mouse protective units, also that a serum of high potency could be diluted many times and still give a typical “swelling” reaction. These experiments suggested a possible quantitative application of the Neufeld reaction.Prelim...