Frontline: Optimal T cell activation requires the engagement of CD6 and CD166

Eur J Immunol. 2004 Apr;34(4):930-40. doi: 10.1002/eji.200424856.


The T cell surface glycoprotein, CD6 binds CD166 in the first example of an interaction between a scavenger receptor cysteine-rich domain and an immunoglobulin-like domain. We report that in human these proteins interact with a K(D) =0.4-1.0 microM and K(off) > or =0.4-0.63 s(-1), typical of many leukocyte membrane protein interactions. CD166 also interacts in a homophilic manner but with around 100-fold lower affinity (K(D) =29-48 microM and K(off) > or = 5.3 s(-1)). At concentrations, that will block the CD6/CD166 interaction, soluble monomeric CD6 and CD166 inhibit antigen-specific human T cell responses. This is consistent with extracellular engagement between CD6 and CD166 being required for an optimal immune response.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Activated-Leukocyte Cell Adhesion Molecule / immunology*
  • Animals
  • Antigen Presentation / immunology*
  • Antigen-Presenting Cells / immunology
  • Antigens, CD / immunology*
  • Antigens, Differentiation, T-Lymphocyte / immunology*
  • Flow Cytometry
  • Humans
  • Lymphocyte Activation / immunology*
  • Polymerase Chain Reaction
  • Rats
  • T-Lymphocytes / immunology*


  • Activated-Leukocyte Cell Adhesion Molecule
  • Antigens, CD
  • Antigens, Differentiation, T-Lymphocyte
  • CD6 antigen