The third bowl of porridge

The paradox of donor T cells in stem cell transplants is that too many may cause graft-versus-host disease, while too few will leave patients with weakened immune systems susceptible to infection and hinder stem cell engraftment. Cerus Corp. believes its S-59 psoralen compound may have found a middle ground that provides a solution.

Psoralens are a class of planar aromatic molecules with a natural affinity for nucleic acids. In the presence of ultraviolet light, the molecules form covalent additions to pyrimidine bases in DNA or RNA - thereby blocking nucleic acid replication...