Constant TCR triggering suggests that the TCR expressed on intestinal intraepithelial γδ T cells is functional in vivo.
Intestinal intraepithelial lymphocytes carrying the γδ TCR (γδ iIEL) are involved in the maintenance of epithelial integrity. γδ iIEL have an activated phenotype, characterized by CD69 expression and increased cell size compared with systemic T lymphocytes. As an additional activation marker, the majority of γδ iIEL express the CD8αα homodimer. However, our knowledge about cognate ligands for most γδ TCR remains fragmentary and recent advances show that γδ T cells including iIEL may be directly activated by cytokines or through NK-receptors, TLR and other pattern recognition receptors. We therefore asked whether the TCR of γδ iIEL was functional beyond its role during thymic selection. Using TcrdH2BeGFP (Tcrd, T-cell receptor δ locus; H2B, histone 2B) reporter mice to identify γδ T cells, we measured their intracellular free calcium concentration in response to TCR-crosslinking. In contrast to systemic γδ T cells, CD8αα(+) γδ iIEL showed high basal calcium levels and were refractory to TCR-dependent calcium-flux induction; however, they readily produced CC chemokine ligand 4 (CCL4) and IFN-γ upon TCR triggering in vitro. Notably, in vivo blocking of the γδ TCR with specific mAb led to a decrease of basal calcium levels in CD8αα(+) γδ iIEL. This suggests that the γδ TCR of CD8αα(+) γδ iIEL is constantly being triggered and therefore functional in vivo.
Hannover Medical School, Institute for Immunology, Hannover, Germany.
Frano H
FH
Malinarich
Elena
E
Grabski
Tim
T
Worbs
Vijaykumar
V
Chennupati
Jan D
JD
Haas
Susanne
S
Schmitz
Enzo
E
Candia
Rodrigo
R
Quera
Bernard
B
Malissen
Reinhold
R
Förster
Marcela
M
Hermoso
Immo
I
Prinz
D000818:Animals; D019138:Antibodies, Blocking / Q000494:pharmacology; D015703:Antigens, CD / Q000096:biosynthesis; D000945:Antigens, Differentiation, T-Lymphocyte / Q000096:biosynthesis; D016827:CD8 Antigens / Q000096:biosynthesis; D020013:Calcium Signaling / Q000187:drug effects / Q000276:immunology; D002478:Cells, Cultured; D054407:Chemokine CCL4 / Q000378:metabolism*; D007371:Interferon-gamma / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000166:cytology*; D037181:Lectins, C-Type / Q000096:biosynthesis; D008213:Lymphocyte Activation / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D013601:T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D000099192:CD69 Antigens
D019138:Antibodies, Blocking; D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D016827:CD8 Antigens; D054407:Chemokine CCL4; D007371:Interferon-gamma; D037181:Lectins, C-Type; D016692:Receptors, Antigen, T-Cell, gamma-delta; D000099192:CD69 Antigens; C409469:CD8 antigen, alpha chain