Private lives: reflections and challenges in understanding the cell biology of the immune system.

The immune system comprises a variety of cell types whose activities must be carefully regulated to act as a coherent unit for the purpose of host defense. To perform their autonomous functions, immune cells must rely on the same basic organizational features that apply to all cells, although immune cells often exhibit remarkable degrees of specialization and adaptation. The study of these specializations has lagged behind advances in understanding the immune response and cell biology individually. As a result, there are great opportunities, but also great challenges, for new conceptual discoveries by taking a more cell-biological approach to probing the function of the immune system.