Erythrocyte membrane phosphatidylcholine and Rh (D) antigen cryolatency

The extent of binding of anti-D antibody to intact RH (D) positive human erythrocytes at -2.5 degrees was approximately one-third that at 3- degrees. An Arrhenius plot of the temperature dependence of antibody binding showed a clear and reproducible discontinuity at approximately 6-8 degrees. Phospholipase A2 digestion of the intact erythrocytes resulted in a diminution of exclusively phosphatidylcholine (PC) from the membrane, and an approximately parallel loss of Rh antigen activity at 37 degrees to about 50% of the original. An Arrhenius plot showed no change in the temperature dependence below 6-8 degrees but significant diminution above that point suggesting that the outer membrane PC is involved in Rh (D) antigen activity manifested above that temperature.