Survival of MM red cells during hypothermia in two patients with anti-M

The in vivo survival of M(M+N-) red cells in two patients with anti-M was studied during hypothermia. The antibodies were IgM, of low titer, and did not react at 30 degrees C. 51Cr survival studies were performed using 2 ml of labeled blood. There was normal circulation of M(M+N-) cells at 37 degrees C and no accelerated loss of these cells at blood temperatures between 16 and 28 degrees C. One patient received 187 ml of MN (M+N +) red cells when the blood temperature was 25 degrees C without evidence of clinical transfusion reactions and without development of positive direct anti-human globulin test. Hypothermia did not adversely affect the immediate survival of M(M+N-) red cells transfused to patients with anti-M antibodies reactive in vitro below 30 degrees C.