Impaired calcium mobilization and differential tyrosine phosphorylation in intestinal intraepithelial lymphocytes.
Intestinal intraepithelial lymphocytes (iIEL) exhibit a unique activation state characterized by the expression of activation markers and effector functions, but a minimal response to mitogenic signals in vitro. To further characterize this activation status, iIEL were compared with splenic T cells for two key activation signals, calcium mobilization and tyrosine phosphorylation. Calcium mobilization was impaired in iIEL treated with the calcium ionophores ionomycin or A23187, thapsigargin, or by CD3-cross-linking. The calcium mobilization defect is shared by mature and embryonic iIEL. Anti-phosphotyrosine Western blot analysis revealed that the iIEL are able to respond to T-cell receptor (TCR)-mediated signals by tyrosine phosphorylation, although the patterns of phosphorylation differ from those seen in splenic T cells. We conclude that iIEL are unable to mobilize calcium in vitro, which may be due to modulation of TCR-mediated signal transduction pathways by the microenvironment of the intestinal epithelium and/or caused by the standard isolation procedure used to prepare iIEL, which must be considered in future in vitro studies of iIEL function.
Sanchez-Garcia
F J
FJ
Department of Pathology, University of Florida College of Medicine, Gainesville 32610-0275, USA.
Aller
W W
WW
Mccormack
W T
WT
D000818:Animals; D000941:Antigens / Q000276:immunology; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D002455:Cell Division; D002645:Chickens; D004848:Epithelium / Q000276:immunology / Q000378:metabolism; D007413:Intestinal Mucosa / Q000276:immunology / Q000378:metabolism*; D008214:Lymphocytes / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D010766:Phosphorylation; D011948:Receptors, Antigen, T-Cell / Q000276:immunology; D015398:Signal Transduction / Q000276:immunology; D013154:Spleen / Q000276:immunology; D014443:Tyrosine / Q000378:metabolism*
D000941:Antigens; D011948:Receptors, Antigen, T-Cell; D014443:Tyrosine; D002118:Calcium