Class II cytoplasmic and transmembrane domains are not required for class II-mediated B cell spreading

• Published in: Immunology letters Vol. 44; no. 1; pp. 67 - 74
• Main Authors: Wade, William F., Dickman, Dion K., Peterson, Daniel, McCluskey, James, Khrebtukova, Irina
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 1995
• Subjects: Actin; Actins - metabolism; Antibodies, Monoclonal - immunology; Antigen presentation; B cell; B-Lymphocytes - pathology; Cyclic AMP - metabolism; Cytoskeleton; Histocompatibility Antigens Class II - chemistry; Histocompatibility Antigens Class II - immunology; MHC class II; Microscopy, Fluorescence; Protein Kinase C - immunology; Recombinant Fusion Proteins - chemistry; Recombinant Fusion Proteins - immunology; Signal transduction; Signal Transduction - immunology; Tumor Cells, Cultured; Antigen presentation; Ig, immunoglobulin; PKC, protein kinase C; mAb, monoclonal antibody; Cy, cytoplasmic; db cAMP, dibutyryl cAMP; MHC class II; MHC, major histocompatibility complex; Ag, Antigen; B cell; Signal transduction; APC, antigen-presenting cell; Actin; Cytoskeleton
• ISSN: 0165-2478; 1879-0542
• DOI: 10.1016/0165-2478(94)00178-T

B cells cultured on immobilized anti-class II monoclonal antibody (mAb) change from round to flattened cells, with lamellipodia and filopodia. This change in cell morphology, termed ‘spiders’, occurs within 30 min upon culture and is mediated through either I-A or I-E molecules. Class II molecules that are defective in mediating protein kinase C (PKC) due to the deletions of both α and β chain's cytoplasmic (Cy) domain sequences can induce spider formation. B-cell transfectants that express chimeric MHC class II/class I molecules, where the ectodomains are class II sequences and the transmembrane and Cy domains are class I sequences also form spiders when cultured on anti-class II mAb. The spider morphology is not induced by either anti-immunoglobulin (Ig) or anti-MHC class I mAb. Treatment of B cells to increase intracellular cAMP, a component of the class II signaling pathway also results in spider formation with the same kinetics and percent change in the responding population as that induced by anti-class II mAb. Cytochalasin A treatment which disrupts cytoskeletal actin filaments and the tyrosine kinase inhibitor, genistein, both inhibit spider formation. Actin redistributes from a concentric ring in round cells to the ends of the filopodia in the spiders. The mechanism of spider induction
whether resultant from second messengers following class II signaling
or from non-signaling-induced physical interactions of class II with intracellular cytoskeletal components only requires the extracellular domains of class II. The biologic relevance of B-cell spiders is currently not known but has been reported to be associated with class II signal transduction and efficient Ag presentation.