Studies on the isolation of rheumatoid factor.

The need for the isolation of rheumatoid factor in a high state of purity and in sufficient quantity for antiserum production has led to an appraisal of the various purification methods available. Ziff, Brown, Lospalluto, Badin, and McEwen (1956) demonstrated that the sensitized sheep cell agglutinating activity of rheumatoid serum was precipitated in the euglobulin fraction, and Svartz and Schlossmann (1954) showed that this factor precipitated in the "cold globulin" fraction and were thus able to obtain a serologically active but heterogenous concentrate. Later, both these groups of workers applied the cellulose ion exchange resins, diethylaminoethyl and carboyxmethyl cellulose, developed by Peterson and Sober (1956) to further fractionate euglobulin fractions (Lospalluto and Ziff, 1959; Svartz, Carlson, Schlossmann, and Ehrenberg, 1958). Ultracentrifugal studies of rheumatoid sera and euglobulin fractions showed that the factor circulated as a high molecular weight component of sedimentation coefficient 19 or 22S and this property has been used by Kunkel, Franklin, and MullerEberhard (1959) and Heimer, Federico, and Freyberg (1958) to separate rheumatoid factor from lower molecular weight proteins. Most of these workers were able to obtain reasonably pure 19S globulin with a considerable concentration of serological activity. In these investigations, however, little attention was paid to immunochemical analyses of individual proteins, and the relative merits in each step in the concentration of rheumatoid factor were not determined. In the investigations now reported, an attempt has been made to determine the most efficient procedure available for the isolation of rheumatoid factor in a relatively pure form. The recovery of rheumatoid factor activity has been measured after each pro-