Antigenicity and irritancy tests of leukocyte-reduction filters using animal models

We experienced a patient who showed severe allergic symptoms immediately after blood transfusion using a filter for removal of leukocytes. To investigate the cause of this incident, we conducted a maximization test on the antigenicity of substances extracted from filters used for leukocyte removal. The tests were performed in guinea pigs. Acetone extracts were obtained from filters made by three manufacturers (A, B and C) and sensitization and evocation were tested at 10% concentration. It was confirmed that extracts from one filter (B) induced sensitization in guinea pigs. Sensitization of the extracts was also tested at 1%, 0.1% and 0.01%, and was induced at 1% but not at 0.1% and 0.01%. Next, skin irritation and sensitization of the substances were tested using mice. 5%-ethanol extracts were prepared from filters made by 2 manufacturers (A and B) and the extracts (5% or 0.5% concentrations) were injected intradermally into the auricle and the ear swelling was observed 1, 24 and 48 hours and 7 days after injection. Significant ear swelling was induced by the extracts from B-filters. In the skin sensitization test, 5% extracts were injected subcutaneously into the back of mice for 3 continuous days for sensitization, and 0.5% extracts were injected intradermally into the auricle of mice to evoke a response, after which changes in ear swelling were observed. Biphasic ear swelling observed 1 hour (immediate response) and 24 hours (delayed response) after challenge was induced by the extracts from B-filters. In conclusion, our study showed that filters used for leukocyte removal may contain substances that cause skin irritation and sensitization and that antigenicity and irritancy tests of the filters might prevent the adverse reactions after blood transfusion.