title: Expression of beta 2m-free HLA class I heavy chains in neuroblastoma cell lines.
abstract: Flow cytometry with the specific monoclonal antibody (MoAb) L31 was used to analyse the expression of HLA class I heavy chains not bound with beta 2-microglobulin (beta 2m) by neuroblastoma (NB) cell lines IMR-32 and LA-N-1. The cells, which express barely detectable amounts of beta 2m-free (L31-positive molecules) and beta 2m-complexed HLA class I antigens (W6.32- and BBM.1-reactive molecules), expressed MHC class I molecules not bound to light chains upon differentiation with either retinoic acid or serum starvation. The expression was not accompanied by an increase of surface heterodimers. Conversely, recombinant interferon-gamma (rIFN-gamma) treatment led IMR-32 and LA-N-1 cells to almost exclusively express beta 2m-complexes HLA class I heavy chains. Surface beta 2m-free MHC class I molecules displayed a molecular mass of approximately 45 kDa and did not bind exogenously added beta 2m. No changes in the synthesis of either HLA class I and beta 2m mRNAs or of L31 proteins were observed in differentiated NB cells, thus suggesting that the surface exposure of unusual HLA class I antigens is regulated post-translationally. These findings indicate that, in addition to activated lymphocytes, the surface expression of beta 2m-free class I heavy chains is a feature of other cell types, such as NB cells.
authors.affiliation: Dipartimento di Biologia e Genetica per le Scienze Mediche, Università di Milano, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Marozzi
authors.forename: R
authors.initials: R
authors.lastname: Meneveri
authors.forename: G
authors.initials: G
authors.lastname: Bunone
authors.forename: C
authors.initials: C
authors.lastname: De Santis
authors.forename: L
authors.initials: L
authors.lastname: Lopalco
authors.forename: A
authors.initials: A
authors.lastname: Beretta
authors.forename: A
authors.initials: A
authors.lastname: Agresti
authors.forename: A G
authors.initials: AG
authors.lastname: Siccardi
authors.forename: G
authors.initials: G
authors.lastname: Della Valle
authors.forename: E
authors.initials: E
authors.lastname: Ginelli
mesh_terms: D000954:Antigens, Surface / Q000032:analysis; D001483:Base Sequence; D005434:Flow Cytometry; D015395:Histocompatibility Antigens Class I / Q000737:chemistry* / Q000235:genetics / Q000276:immunology*; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000032:analysis; D007371:Interferon-gamma / Q000494:pharmacology; D008969:Molecular Sequence Data; D009447:Neuroblastoma / Q000235:genetics / Q000276:immunology* / Q000473:pathology; D012333:RNA, Messenger / Q000032:analysis; D014407:Tumor Cells, Cultured / Q000187:drug effects; D001613:beta 2-Microglobulin / Q000032:analysis* / Q000378:metabolism
chemical_list: D000954:Antigens, Surface; D015395:Histocompatibility Antigens Class I; D007143:Immunoglobulin Heavy Chains; D012333:RNA, Messenger; D001613:beta 2-Microglobulin; D007371:Interferon-gamma