Imperial College London


Faculty of MedicineDepartment of Immunology and Inflammation

Visiting Professor



+44 (0)20 7594 1190g.screaton Website




Ms Claire Puddephatt +44 (0)20 7594 1190




2.15Faculty BuildingSouth Kensington Campus






BibTex format

author = {Jonsson, P and Southcombe, JH and Santos, AM and Huo, J and Fernandes, RA and McColl, J and Lever, M and Evans, EJ and Hudson, A and Chang, VT and Hanke, T and Godkin, A and Dunne, PD and Horrocks, MH and Palayret, M and Screaton, GR and Petersen, J and Rossjohn, J and Fugger, L and Dushek, O and Xu, X-N and Davis, SJ and Klenerman, D},
doi = {10.1073/pnas.1513918113},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
pages = {5682--5687},
title = {Remarkably low affinity of CD4/peptide-major histocompatibility complex class II protein interactions},
url = {},
volume = {113},
year = {2016}

RIS format (EndNote, RefMan)

AB - The αβ T-cell coreceptor CD4 enhances immune responses more than 1 million-fold in some assays, and yet the affinity of CD4 for its ligand, peptide-major histocompatibility class II (pMHC II) on antigen-presenting cells, is so weak that it was previously unquantifiable. Here, we report that a soluble form of CD4 failed to bind detectably to pMHC II in surface plasmon resonance-based assays, establishing a new upper limit for the solution affinity at 2.5 mM. However, when presented multivalently on magnetic beads, soluble CD4 bound pMHC II-expressing B cells, confirming that it is active and allowing mapping of the native coreceptor binding site on pMHC II. Whereas binding was undetectable in solution, the affinity of the CD4/pMHC II interaction could be measured in 2D using CD4- and adhesion molecule-functionalized, supported lipid bilayers, yielding a 2D Kd of ∼5,000 molecules/μm2. This value is two to three orders of magnitude higher than previously measured 2D Kd values for interacting leukocyte surface proteins. Calculations indicated, however, that CD4/pMHC II binding would increase rates of T-cell receptor (TCR) complex phosphorylation by threefold via the recruitment of Lck, with only a small, 2–20% increase in the effective affinity of the TCR for pMHC II. The affinity of CD4/pMHC II therefore seems to be set at a value that increases T-cell sensitivity by enhancing phosphorylation, without compromising ligand discrimination.
AU - Jonsson,P
AU - Southcombe,JH
AU - Santos,AM
AU - Huo,J
AU - Fernandes,RA
AU - McColl,J
AU - Lever,M
AU - Evans,EJ
AU - Hudson,A
AU - Chang,VT
AU - Hanke,T
AU - Godkin,A
AU - Dunne,PD
AU - Horrocks,MH
AU - Palayret,M
AU - Screaton,GR
AU - Petersen,J
AU - Rossjohn,J
AU - Fugger,L
AU - Dushek,O
AU - Xu,X-N
AU - Davis,SJ
AU - Klenerman,D
DO - 10.1073/pnas.1513918113
EP - 5687
PY - 2016///
SN - 1091-6490
SP - 5682
TI - Remarkably low affinity of CD4/peptide-major histocompatibility complex class II protein interactions
T2 - Proceedings of the National Academy of Sciences of the United States of America
UR -
UR -
UR -
VL - 113
ER -