Isoimmunity to Blood Platelets in the Rabbit

The occurrence of platelet isoimmunity was studied in rabbits sensitized by 3 to 12 transfusions of homologous blood. Platelet isoimmunity in the transfused animals was detected and measured by two different technics: (1) determination of the survival of homologous platelets labeled in vivo with P³² and infused in the sensitized recipient rabbits; and (2) study of platelet agglutinins in the serum of the multitransfused animals.

It was found that:

1. After 3 to 12 blood transfusions, platelet sensitization, as determined by reduction in survival of homologous platelets in the transfused rabbits, occurred in most animals.

2. Survival of homologous specific platelets, i.e., platelets collected from the sensitizing donor and infused in the respective recipient, usually had lower values than the survival of homologous non-specific platelets.

3. Higher degrees of depression in survival of homologous platelets were found in the rabbits which had received larger numbers of blood transfusions.

4. Platelet isoagglutinins could be found only in three of the five rabbits which had been sensitized with 12 blood transfusions and the test was strongly positive in only one rabbit.

5. Repeat studies performed 2½ months after the transfusions demonstrated persistence of platelet isosensitization, while after 15 months isosensitization had greatly decreased; although in one rabbit a good degree of depression in homologous platelet survival wa still present after this time interval.

These studies mainly demonstrate the high frequency of platelet isoimmunity in multitransfused rabbits and the inadequacy of the agglutinin test in the detection of even relatively severe degrees of platelet isosensitization.