Daisy chains: cyclosporine link.

The normally round nuclei of white blood cells known as helper T lymphocytes take on a daisy shape (above) after exposure to cyclosporine, an immune-suppressive drug. The morphological change suggests that cyclosporine alters the matrix supporting the chromosomes in the nucleus, says one of the phenomenon's discoverers, Allan Hess of Johns Hopkins University in Baltimore. And by doing so, he suggests, the drug halts genetic activity in the helper T cells, the orchestrators of the immune system.

The unusual shape change has also been reported in the nuclei of helper T lymphocytes infected by HTLV-I and -II, two leukemia-causing viruses related but not identical to the AIDS-associated virus, known variously as HTLV-III, LAV and ARV. But with the viral infection the change is irreversible, whereas two hours after cyclosporine exposure ends, the nuclei return to their round shape.

On the biochemical level, Hess and his colleagues have found that cyclosporine binds to calmodulin, a cell protein with many functions. The binding, they previously reported in the April 9 SCIENCE, is a necessary step in the cell's activation and replication, and can be interpreted by cyclosporine. A report of the shape change is scheduled to appear in the January 1986 JOURNAL OF CELL BIOLOGY.