The Long and the Short of It

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Science  04 May 2001:
Vol. 292, Issue 5518, pp. 811
DOI: 10.1126/science.292.5518.811e

Rapid clonal expansion is used to generate sufficient numbers of antigen-specific lymphocytes to deal with pathogens. For T cells, this expansion originates through contact with antigen-presenting cells in the lymph nodes, from where dividing antigen-primed T cells move rapidly to contain infection at peripheral sites.

Two studies, by Kaech and Ahmed and by van Stipdonk et al., now suggest a means by which CD8+ T cells balance the need for antigen-driven expansion with the need for rapid deployment to sites of infection. It might be predicted that dose and length of exposure to antigen would dictate the extent of cell division and differentiation undertaken by naïve CD8+ T cells. Instead, however, a short initial encounter with antigen was sufficient to induce naïve T cells to commit to a differentiation program including a minimum of seven cell divisions, resulting in the acquisition of effector and memory cell characteristics. Similar results were found when the length of antigen exposure was carefully regulated. This programming of CD8+ T cells to expand and differentiate independently of antigen-presenting cells after a fleeting first encounter with antigen makes much immunological sense as a strategy for coping with infection. — SJS

Nature Immunol.2, 415; 423 (2001).

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