The New Encyclopaedia Britannica (1998 Edition) states that,
"Most of the leukocytes are outside the circulation, and the few in the bloodstream are in transit from one site to another".
This means that if a brother accepts an organ transplant (which is permitted), he will receive into his body many times more white cells than if he had them as a transfusion (which is not permitted).
Consider also that fractions like albumin have been deemed a matter of conscience by the Society on the consideration that such pass naturally from mother to child in the womb. However leukocytes also pass naturally from mother to child during breastfeeding, particularly in the first few days when colostrum is produced. On this matter, La Leche League International state,
"Colostrum also contains high concentrations of leukocytes, protective white cells which can destroy disease-causing bacteria and viruses".
The highly respected British Medical Association in their Complete Family Health Encyclopaedia state on page 291 under the heading 'COLOSTRUM',
"It has a high content of lymphocytes (white blood cells) and immunoglobulins, which help protect the baby from infection".