Background: The functional importance of CD2 in vivo is currently the subject of discussion.
Objective: To describe a 47-year-old white man with systemic Rhodococcus infection, a rarely observed opportunistic disease, secondary to severe lymphopenia.
Methods: We extensively characterized lymphocyte phenotype and function.
Results: Both CD4+ and CD8+ T cells were severely diminished, with a particular reduction in alpha:beta T cells. Human immunodeficiency virus infection was excluded. CD2 expression was decreased not only on T cells but also on nonaffected natural killer cells. Production of interferon-gamma interleukin 2, and tumor necrosis factor a was normal. Neither B-cell numbers nor humoral immune responses were affected. In addition, adhesion molecules CD11a, CD54, and CD154 were normally expressed, as were the costimulatory molecules CD28, CD80, and CD86.
Conclusions: We hypothesize that prolonged disturbance of CD2 expression led to an acquired severe cellular immunodeficiency. This underlines the importance of CD2 in vivo, where it may play a role in the fine regulation of T-cell proliferation.