Cold-fighting cells.

The immune system has two ways of dealing with foreign invaders--with a genearlized response, called cellular immunity, and a more specific response that involves antibodies. Susan C. Kiley and her colleagues at the Food and Drug Administration in Bethesda, Md., and George Washington University in Washington, D.C., are studying the action of cytotoxic T lymphocytes, cellular immune responders that attack foreign or infected cells. They have found a genetic factor in the ability of the cellular immune system to fight flu viruses.

They added T lymphocytes from 51 people to influenza-A infected cells. Cell types were defined by their HLA genes, a set of genes coding for proteins involved in cell recognition. There was a correlation between genetic subtype and disease-fighting ability -- cells bearing HLA-DR4 genes were better able to kill infected cells, and HLA-DR7 cells were less able, than the rest of the subtypes tested. "The cells of some people seem to be more reactive in response to infection by viruses than others," says Kiley. "We speculate that means they're more protective, but that would have to be followed up in future studies."