The nuances of lymphocytopenia.

We have discussed the causes of lymphocytopenia and attempted to categorize them according to pathogenesis. This effort may be tenuous at best, because so much is still unknown about lymphocyte function and kinetics. In describing pathogenesis we have reported what has been published and not speculated on mechanisms when they were not stated. Many of these reports were decades apart, and the technical resources available to the investigators were varied. We suspect, for example, that many of the lymphocyte changes secondary to inflammation and infection will have a common pathogenesis (for example, cytokines and endotoxins). Undoubtedly, the picture will become much clearer in the years ahead.