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°C. 51Cr survival studies were performed using 2 ml of labeled blood. There was normal circulation of M(M+N—) cells at 37°C and no accelerated loss of these cells at blood temperatures between 16 and 28°C. One patient received 187 ml of MN (M+N+) red cells when the blood temperature was 25°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°C