They also said the regulators had concerns about possible immune reactions to the drug, though none were seen.
He was best known for his research on the relationship between the white cells in the blood and immune reactions.
It is a result of an immune reaction to infection by group A streptococcus.
They provoke none of the immune reactions in the body that result from other infections.
Questions also have been raised about potential long-term risks like immune reactions and cancer.
Cells whose protein would cause an immune reaction with the body, are removed.
In some cases the immune reaction may be fatal.
Research in 2004 suggested that the disease is due to an immune reaction.
The most likely cause is an immune reaction the body has against its own intestinal tissue.
Concerns about adverse immune reactions are "not much of an issue," he said.
