The downside to lymphocytes

Lymphocytes are required to fight off invading microbes—T cells to seek out and kill infected cells, and B cells to produce pathogen-specific antibodies. But a study by Carrero and colleagues (page 933) suggests that, in some situations, having lymphocytes is not such a good thing.

Two decades ago, this group showed that lymphocyte-deficient mice are up to 1,000 times better than normal mice at controlling bacterial growth during the first few days of infection with Listeria monocytogenes. They speculated that mice born without lymphocytes might have developed a more efficient innate immune response—much like people who are born blind develop a heightened sense of smell and more acute hearing. This idea made sense because innate immune cells—such as macrophages and neutrophils—are responsible for killing the bacteria during the initial...