IL-4 is able to reverse the CD2-mediated negative apoptotic signal to CD4-CD8- alpha beta and/or gamma delta T lymphocytes.
Activation of immature thymocytes or transformed T lymphocytes via T-cell receptor (TCR)/CD3 signalling can induce programmed cell death (apoptosis). Recent data indicate that anti-CD3/TCR monoclonal antibodies (mAb) also trigger apoptosis in activated (but not resting) mature peripheral blood T lymphocytes. Here we report that triggering of resting CD4-CD8-TCR alpha beta+ and/or TCR gamma delta+ via the alternative CD2-dependent activation pathway is able to induce programmed cell death. A pair of mitogenic anti-CD2 mAb provoked a dramatic rise in [Ca2+]i that was almost entirely sustained by extracellular fluxes, and the inhibition of membrane [Ca2+/Mg2+] ATPase. The resulting endonuclease activation was able to induce DNA fragmentation, as revealed by propidium iodide staining and gel electrophoresis. Induction of apoptosis was prevented by the presence of interleukin-4 (IL-4) as well as by endonuclease inactivation with 100 microM ZnCl2, but enhanced by the contemporary block of protein kinase C. Thus it seems that in resting T lymphocytes the strong calcium signal delivered by the alternative CD2 activation pathway may act as a negative apoptotic signal in both alpha beta and gamma delta T cells with low (non-major histocompatibility complex restricted) antigenic affinity, so limiting the extension of polyclonal T-cell growth.
Spinozzi
F
F
Department of Internal Medicine, University of Perugia, Italy.
Nicoletti
I
I
Agea
E
E
Belia
S
S
Moraca
R
R
Migliorati
G
G
Riccardi
C
C
Grignani
F
F
Bertotto
A
A
D000911:Antibodies, Monoclonal; D017209:Apoptosis / Q000276:immunology; D018801:CD2 Antigens / Q000378:metabolism*; D015704:CD4 Antigens; D016827:CD8 Antigens; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002478:Cells, Cultured; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D015847:Interleukin-4 / Q000378:metabolism*; D008213:Lymphocyte Activation; D018655:Lymphocyte Count; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000378:metabolism*; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D016176:T-Lymphocyte Subsets / Q000276:immunology; D013601:T-Lymphocytes / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D018801:CD2 Antigens; D015704:CD4 Antigens; D016827:CD8 Antigens; D016693:Receptors, Antigen, T-Cell, alpha-beta; D016692:Receptors, Antigen, T-Cell, gamma-delta; D015847:Interleukin-4; D015544:Inositol 1,4,5-Trisphosphate; D000252:Calcium-Transporting ATPases; D002118:Calcium