Distinct patterns of transmembrane calcium flux and intracellular calcium mobilization after differentiation antigen cluster 2 (E rosette receptor) or 3 (T3) stimulation of human lymphocytes.
We evaluated CD2 (E rosette) and CD3 (T3)-triggered activation of resting lymphocytes by measuring the intracellular free calcium concentration ([Ca2+]i) of individual cells. The [Ca2+]i of indo-1-loaded cells was measured by flow cytometry and responses were correlated with cell surface phenotype. Stimulation with anti-CD3 antibody caused an increase in [Ca2+]i in greater than 90% of CD3+ cells within 1 min, and furthermore, the response was restricted to cells bearing the CD3 marker. In contrast, stimulation of cells with anti-CD2 antibodies produced a biphasic response pattern with an early component in CD3- cells and a late component in CD3+ cells. Thus, the CD2 response does not require cell surface expression of CD3. In addition, stimulation of a single CD2 epitope was sufficient for activation of CD3- cells, whereas stimulation of two CD2 epitopes was required for activation of CD3+ cells. Both the CD2 and CD3 responses were diminished in magnitude and duration by EGTA. However, approximately 50% of T cells still had a brief response in the presence of EGTA, indicating that the increased [Ca2+]i results in part from intracellular calcium mobilization, and furthermore demonstrates that extracellular calcium is required for a full and sustained response. Our results support the concept that CD2 represents the trigger for a distinct pathway of activation both for T cells that express the CD3 molecular complex and for large granular lymphocytes that do not.
C H
CH
June
J A
JA
Ledbetter
P S
PS
Rabinovitch
P J
PJ
Martin
P G
PG
Beatty
J A
JA
Hansen
D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D000939:Epitopes / Q000276:immunology; D005434:Flow Cytometry; D006801:Humans; D007700:Kinetics; D008214:Lymphocytes / Q000187:drug effects*; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism
D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface; D000939:Epitopes; D011948:Receptors, Antigen, T-Cell; D002118:Calcium