CD40L+ CD4+ memory T cells migrate in a CD62P-dependent fashion into reactive lymph nodes and license dendritic cells for T cell priming.

Martín-Fontecha A, Baumjohann D, Guarda G, Reboldi A, Hons M, Lanzavecchia A, Sallusto F.
J Exp Med. 2008 Oct 27;205(11):2561-74. Epub 2008 Oct 6.

There is growing evidence that the maturation state of dendritic cells (DCs) is a critical parameter determining the balance between tolerance and immunity. We report that mouse CD4(+) effector memory T (T(EM)) cells, but not naive or central memory T cells, constitutively expressed CD40L at levels sufficient to induce DC maturation in vitro and in vivo in the absence of antigenic stimulation. CD4(+) T(EM) cells were excluded from resting lymph nodes but migrated in a CD62P-dependent fashion into reactive lymph nodes that were induced to express CD62P, in a transient or sustained fashion, on high endothelial venules. Trafficking of CD4(+) T(EM) cells into chronic reactive lymph nodes maintained resident DCs in a mature state and promoted naive T cell responses and experimental autoimmune encephalomyelitis (EAE) to antigens administered in the absence of adjuvants. Antibodies to CD62P, which blocked CD4(+) T(EM) cell migration into reactive lymph nodes, inhibited DC maturation, T cell priming, and induction of EAE. These results show that T(EM) cells can behave as endogenous adjuvants and suggest a mechanistic link between lymphocyte traffic in lymph nodes and induction of autoimmunity.

URL: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2571931/?tool=pubmed

Pub Med: http://www.ncbi.nlm.nih.gov/pubmed/18838544

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