T cells don't fight infections from particular viruses or bacteria until they somehow perceive that they are needed. Special cells, called antigen-presenting cells (APCs), get the T cell's attention with very specific, tiny, bits of pathogen. In the January issue of Nature Immunology, scientists from Stanford University show that, paradoxically, to achieve the strongest response, completely unrelated bits of protein, normally from the host itself, must also be carried into the zone of contact between the two cells, called the "immunological synapse".
This surprising result was found during a study of the discrete geometrical patterns of key receptor-ligand molecules that accumulate at the immunological synapse. Mark Davis and colleagues tracked the nonspecific bits (peptides), by fluorescently tagging the molecule that offers the bits to the T cell, the major histocompatibility complex (MHC) proteins. They then used video microscopy to directly watch the peptide-MHC complexes flow along the surface and form the synapse. Even though the "nonspecific bits" of peptides in their test system could not contact the T cell recognition unit itself (they are considered nonspecific because they don't have the right shape to make the contacts), they accumulated in the synapse anyway and enhanced the activation of the T cell. Illuminating this intricate dance at the interface has revealed, therefore, that although specificity is the bedrock upon which all of T cell biology is understood, the system cannot function optimally without contributions from the nonspecific, as well.
Mark M. Davis
Howard Hughes Medical Institute
Stanford, CA, USA
Tel: +1 650 725-4755
Additional contact for comment on paper:
P. Anton van der Merwe
Sir William Dunn School of Pathology
Oxford, United Kingdom
(C) Nature Immunology press release.
Message posted by: Trevor M. D'Souza
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