Salivary gland epithelial cells (SGEC): carriers of exquisite B7-2 (CD86) costimulatory molecules.
Costimulatory molecules are cell-surface glycoproteins that can direct, modulate and fine tune immune responses. B7-2(CD86) costimulatory molecules are considered as major regulators of T cell responses, acting by appropriate interactions with the stimulatory CD28 or inhibitory CTLA-4 receptors found on T cells. Although their expression is thought to be restricted in lymphoid cells, evidence raised during the last decade show their expression in other types of cells, including human non-neoplastic salivary gland epithelial cells (SGEC). The expression of B7-2 molecules by SGECs requires special attention, due to their unique expression pattern and distinctive binding properties. Thus, SGECs express three B7-2 alternate transcripts that encode the full-length protein, the soluble form and a truncated membrane-bound molecule, that lacks the IgV-like counter-receptor binding domain and has a negative regulatory role. A similar pattern of expression is observed in monocytes, but not in several other types of cells, including dendritic cells. Furthermore, the full-length B7-2 molecules in SGEC display unique binding properties, denoted by the functional interaction with CD28 receptor, but reduced binding of the negative regulator CTLA-4. These distinctive features suggest the tight regulation of B7-2 molecules expression and indicate the key immunoregulatory role of SGECs.
Kapsogeorgou
Efstathia K
EK
Department of Pathophysiology, School of Medicine, National University of Athens, Greece. ekapso@med.uoa.gr
Manoussakis
Menelaos N
MN
D017398:Alternative Splicing; D015703:Antigens, CD / Q000378:metabolism; D051940:B7-2 Antigen / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D018106:CD28 Antigens / Q000378:metabolism*; D060908:CTLA-4 Antigen; D004847:Epithelial Cells / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D025461:Feedback, Physiological; D020869:Gene Expression Profiling; D006801:Humans; D018448:Models, Immunological; D009000:Monocytes / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D011485:Protein Binding / Q000235:genetics; D020033:Protein Isoforms / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D012469:Salivary Glands / Q000473:pathology; D012859:Sjogren's Syndrome / Q000276:immunology*
D015703:Antigens, CD; D051940:B7-2 Antigen; D018106:CD28 Antigens; D060908:CTLA-4 Antigen; C556706:CTLA4 protein, human; D020033:Protein Isoforms