Dose-Dependent Destruction of A1 Cells by Anti-A1

Abstract. In a patient of subgroup A₂ the serum contained an unusually potent anti-A₁, giving the following reactions with A₁ red cells in vitro: agglutination of saline-suspended cells up to a temperature of 32°C; a positive indirect antiglobulin test (complement only) at 37°C and lysis of enzyme-treated cells at 37°C. A series of tests was carried out to estimate the ability of the antibody to destroy varying amounts of A₁ red cells in vivo . When about 0.55 ml of red cells was injected, about 65% of the cells were destroyed within 30 min; 2 days later when 18.9 ml of cells were injected, only about 45% were destroyed within 30 min; 5 days after this when a whole unit of A₁ red cells was transfused, survival at 24 h was about 90%. This last figure may indicate that destruction of red cells by anti-A₁ was negligible since at the time of the transfusion of the whole unit the patient was bleeding into her gastrointestinal tract. On the other hand, the titre of anti-A₁ appeared to be declining spontaneously during the period in which tests were carried out so that, if the whole unit of A₁ blood had been transfused at the beginning of this period, survival might have been less good. Nevertheless, from the observed difference in survival between the 0.55 ml and 18.9 ml doses it seems safe to conclude that, even if the unit had been transfused at the time when the antibody concentration was maximal, the percentage of cells destroyed would have been small.