The National Institutes of Health researchers said the protein enables T and B cells to interact in a way that's crucial to establishing long-lasting immunity after an infection. Their finding, they said, might explain why some individuals who have a genetic defect that prevents them from making the protein -- called SAP -- suffer from lethal infections with a common virus that otherwise is rarely fatal, while others with the genetic defect have problems with B-cell lymphomas.

The research that included Dr. Ronald Germain at the National Institute of Allergy and Infectious Diseases and Dr. Pamela Schwartzberg of the National Human Genome Research Institute -- both NIH facilities -- is reported in the journal Nature.