The agglutinating factor for sensitized sheep erythrocytes in serum and joint fluid from rheumatoid arthritis patients.

On May 6, 1949, a preliminary account was given before the Swedish Society for Internal Medicine of a special method for the sheep-cell agglutination test based on experiments made by the authors (Svartz and Schlossmann, 1949). A similar account was presented to the Seventh International Congress on Rheumatic Diseases, New York, 1949. First we must emphasize the fact that all human sera contain heterophil haemagglutinins which agglutinate normal (unsensitized) red sheep cells. In certain diseases such agglutinins occur in a higher titre than in the serum of healthy persons. These heterophil agglutinins can always be absorbed by normal sheep cells. In rheumatoid arthritis, and in isolated cases of other diseases, there exists in the blood another type of agglutinating factor, not absorbable by normal sheep cells and unable to agglutinate them. This factor only agglutinates sheep cells which have been sensitized with a small amount of rabbit anti-sheelp-cell serum (amboceptor). The agglutination with normal sheep cells is inhibited by extract from the kidneys of guinea-pigs. This is not the case with the agglutination with sensitized sheep cells. Since February, 1949, the present authors have been studying the agglutinating factor for sensitized sheep cells by an absorption method, which has not hitherto been described in detail. Absorption Method The fresh serum or synovial fluid under test was inactivated in a water bath for 30 minutes at 560 C. For each test, 1 * 5 ml. serum or synovial fluid, 1 *5 ml. packed sheep cells (obtained from fresh defibrinated blood and washed three times with sterile normal saline), and 1 * 5 ml. 0 * 85 per cent. NaCl solution were thoroughly mixed in a tube with a rounded bottom. The mixture was incubated in a water bath for 2 hours at 370 C., being shaken thoroughly several times, and was then kept overnight at 40 C. After centrifugation at 2,000 revolutions per minute for 20 minutes, the supernatant fluid was pipetted off and used for the agglutination test with normal and sensitized sheep cells.