The B7 adhesion molecule is expressed on activated human T cells: functional involvement in T-T cell interactions.
The B cell antigen B7 delivers a strong co-stimulatory signal for the activation of T cells by binding to its ligands CD28 and CTLA4. Here we demonstrate the surface expression of the B7 molecule on activated human T cells in vitro and under certain conditions in vivo and its functional importance in T-T cell interactions. B7 was detected by flow cytometry on antigen-specific CD4+ and allospecific CD8+ cloned T cells from different donors with anti-B7 monoclonal antibody (mAb) or a soluble CTLA4-C gamma 1 chimera molecule and by reverse transcription-polymerase chain reactions. The expression of B7 was up-regulated following restimulation of the T cell clones and peaked after 7-9 days. Moreover, we show that the B7 molecule on T cells is functionally involved in T-T cell interactions: mAb to CD28 and the CTLA4-Ig fusion protein could inhibit the proliferation of specific T cell clones in response to T cells as antigen-presenting cells (APC) or the proliferation of peripheral blood mononuclear cells in a primary allostimulation with activated T cells as stimulator cells. Finally, we found that B7 can be expressed on freshly isolated circulating T cells since in a preliminary study with a limited number of patients, B7 was present on a subset of CD3+ cells. B7 was expressed on activated T cells (CD4+ and CD8+) of certain human immunodeficiency virus (HIV)-infected individuals (0.5-20% B7+CD8+ cells) or some patients with autoimmune diseases whereas CD3+ cells of healthy individuals did not express B7. The coexpression of major histocompatibility complex class II molecules and B7 may be relevant for the capacity of activated T cells to function as APC. The expression of B7 on T cells in vivo in autoimmune diseases and in HIV infection may be important for a better understanding of these diseases.
Wyss-Coray
T
T
Institute of Clinical Immunology, Inselspital, Switzerland.
Mauri-Hellweg
D
D
Baumann
K
K
Bettens
F
F
Grunow
R
R
Pichler
W J
WJ
D000954:Antigens, Surface / Q000032:analysis* / Q000235:genetics / Q000502:physiology; D018122:B7-1 Antigen; D001483:Base Sequence; D015815:Cell Adhesion Molecules / Q000032:analysis*; D002450:Cell Communication; D002460:Cell Line; D006801:Humans; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis; D013601:T-Lymphocytes / Q000276:immunology* / Q000502:physiology; D015854:Up-Regulation
D000954:Antigens, Surface; D018122:B7-1 Antigen; D015815:Cell Adhesion Molecules; D012333:RNA, Messenger