Research: Size is important

7 November 2005

Activation of T cells seems to depend on an intimate interaction between T cell and antigen-presenting cell.

Activation of T cells is a crucial part of our immune response. T cells are activated when an antibody-like surface protein (the T-cell receptor) comes into contact with a specific small peptide from a target microbe. This peptide is 'presented' to the T cell: it sits within a special groove in a major histocompatibility complex (MHC) protein on the surface of an antigen-presenting cell.

How this interaction between T-cell receptor and MHC–peptide complex activates the T cell has been controversial. Of particular contention has been the importance of the size of other externally facing molecules around the T-cell receptor.

Kaushik Choudhuri, a Wellcome Training Fellow in Anton van der Merwe's lab in Oxford, has with colleagues now shown that increasing the size of the MHC–peptide complex inhibits T-cell activation without affecting the interaction between the complex and the T-cell receptor. The small size does therefore appear to be important. The authors suggest that size-based segregation of complexes at the T-cell surface is important for kick-starting the T cell.

External links

Choudhuri K et al. T-cell receptor triggering is critically dependent on the dimensions of its peptide–MHC ligand. Nature 2005;436(7050):578–82.