Flow cytometry with the specific monoclonal antibody (MoAb) L31 was used to analyse the expression of HLA class I heavy chains not bound with β2-microglobulin (β2m) by neuroblastoma (NB) cell lines IMR-32 and LA-N-1. The cells, which express barely detectable amounts of β2m-free (E31-positive molecules) and β2m-complexed HLA class 1 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-γ (rIFN-γ) treatment led IMR-32 and LA-N-1 cells to almost exclusively express β2m-complexed HLA class I heavy chains. Surface β2m-free MHC class I molecules displayed a molecular mass of ~45 kDa and did not bind exogenously added β2m. No changes in the synthesis of either HLA class I and β2m 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 β2m-free class I heavy chains is a feature of other cell types, such as NB cells.
|Number of pages||7|
|Journal||Scandinavian Journal of Immunology|
|Publication status||Published - 1993|
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