Recent evidence supports the idea that T cells in neonatal animals are developmentally mature in their capacity to mount protective helper and cytotoxic responses. Nonetheless, neonates fall prey to infections which have little effect on adults and they often fail to mount mature responses to environmental, experimental, or vaccine antigens. To reconcile these observations, it may be important to consider the potential role of apoptosis in neonatal immune responses. In adults, apoptosis is well established as a centrally important process in the homeostasis of cellular immune responses. Activated T cells deprived of IL-2 undergo cytokine withdrawal-induced apoptosis. Previously activated T cells can also be triggered by secondary stimulation to undergo activation induced apoptosis. This review summarizes our current state of knowledge of apoptosis of murine neonatal T cells and discusses the possible impact(s) of this apoptosis on neonatal immune responses in vivo.
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