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Science 5 November 1999:
Vol. 286. no. 5442, p. 1049
DOI: 10.1126/science.286.5442.1049q
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Not all T cells are alike. One of the first developmental commitments a T cell must make is whether it will ultimately express CD4 or CD8, proteins that mark mature T cells primarily as "helpers" or "killers," respectively. Because this lineage decision is made at about the time when immature cells are selected to either live (positive selection) or die (negative selection), based on the specificity of their antigen receptors, these two decisions could be inextricably linked. Keefe et al. (p. 1149) used a mutant mouse, HD, that does not have CD4 cells to investigate this question. The T cells that normally would be CD4 instead entered the CD8 lineage, yet their positive selection was normal. Thus, these two processes are not linked.




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Science. ISSN 0036-8075 (print), 1095-9203 (online)