Corticosteroids are known to inhibit NK cell functions. However no information is available on whether such inhibition may affect the expression and/or the function of receptors involved in NK cell activation. In an attempt to analyze this point, we studied peripheral blood NK cells isolated from pediatric patients undergoing allogeneic BM transplantation. NK cells were analyzed before, during and after methylprednisolone administration to treat acute graftversus-host disease. In NK cells freshly isolated from peripheral blood during methylprednisolone treatment, the surface expression of activating receptors, particularly NKp46 and NKp30, was consistently reduced. Such impaired expression could also be detected after 5 days of culture in IL-2. Such cultured NK cells also failed to express the IL-2-inducible NKp44 receptor. Accordingly, cytotoxicity against different tumor target cell lines was sharply reduced. The effect on NK cells isolated from healthy individuals and cultured in the presence of methylprednisolone was also analyzed. A similar inhibitory effect occurred in the expression of activating NK receptors. In addition, a sharp impairment of NK cytotoxicity against different tumor target cell lines or immature DC was detected.

Upon specific recognition of HLA class I molecules, the HLA class I-specific inhibitory receptors suppress NK-cell cytolytic activity, whereas target-cell lysis will require a partial or complete downregulation of HLA class I molecules. [3][4][5][6][7] Several structurally different activating receptors are involved in NK cell-mediated cytotoxicity. The CD16 receptor, expressed on the majority of peripheral-blood NK cells, mediates antibodydependent cytotoxicity (ADCC) against IgG-coated target cells. CD16 associates with CD3 and Fc⑀R␥, which carry cytoplasmic immunoreceptor tyrosine-based activation motifs (ITAMs). 8 NKmediated lysis of tumor cells or virus-infected cells is mainly mediated by NKp46, NKp30, and NKp44 (collectively referred to as natural cytotoxicity receptors [NCRs]) and by NKG2D. 5,[9][10][11] NKp46 and NKp30 are present on both resting and activated NK cells, whereas NKp44 is expressed only upon NK-cell activation. NKp30 and NKp46 deliver intracellular signals, thanks to their association with CD3 or CD3 plus Fc⑀R␥, respectively, whereas NKp44 associates with the KARAP/DAP12 molecules. 12 Other activating receptors include DNAM-1, 2B4, NTBA, and NKp80. Notably, 2B4, NTBA, and NKp80 are considered coreceptors, as they can significantly increase the NK-cell cytotoxicity against some cellular targets when they are coengaged with NCRs or NKG2D. [13][14][15][16][17] It is evident that the surface expression of activating receptors is crucial for the NK-mediated killing of various target cells. Therefore, it appeared conceivable that immunosuppressive drugs such as glucocorticoids (GCs) could impair the NK-cell function by affecting the surface expression and/or the function of activating NK receptors. In this context, we have recently shown that pediatric patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT) display a profound down-regulation of most activating NK receptors and coreceptors and an impaired cytolytic activity. This effect appeared to be related to the administration of methylprednisolone (MePDN) to treat graftversus-host disease (GvHD). Indeed, in vitro analysis of NK cells from healthy donors confirmed that MePDN could induce both down-regulation of the NKp30 and NKG2D activating NK receptors and a sharp impairment of NK-cell function. Moreover, in spite of its unaltered surface expression, NKp46 failed to efficiently transduce triggering signals. 18 In this context, however, it should be stressed that NK-cell cytotoxicity is a complex process that requires adhesion to target cells, synapse formation, signal transduction leading to granule polarization, and exocytosis. Accordingly, it is conceivable that MePDN might also interfere with different steps of this process.In previous studies, GCs have been shown to inhibit different T-cell functional activities (including proliferation, cytotoxicity, The online version of this article contains a data supplement.The publication costs of this article were defrayed in part by page charge payment. Therefore, and sole...

BACKGROUND AND PURPOSE: Intra-arterial chemotherapy for retinoblastoma is not always a straightforward procedure, and it may require an adaptable approach. This study illustrates strategies used when the ophthalmic artery is difficult to catheterize or not visible, and it ascertains the effectiveness and safety of these strategies.

The HLA-DR expression pattern in mild and moderate dry eyes appears to reflect disease progression. Overexpression of HLA-DR in mild dry eyes showing no vital staining suggests that inflammation may be a primary cause of ocular surface damage. These data support the use of immunomodulatory drugs in the treatment of dry eye disease.

Patients undergoing allogeneic bone marrow transplantation offer a unique system to analyze NK cell development in vivo. We analyzed NK cells from 23 such patients to assess the acquisition of activating receptors. Four patients displayed an immature NK cell surface phenotype at engraftment, as their cells were CD16 -KIR -and NKG2D -but expressed low levels of NKp46, NKp30, 2B4 and NKG2A. These NK cells had particularly low cytolytic activity against the HLA-class-I -melanoma F01 cell line and the 721-221 EBV-infected B cell line. Moreover, cytoxicity was inhibited upon mAb-mediated crosslinking of 2B4. Analysis of NK cells at day 30 after bone marrow transplantation revealed the occurrence of both phenotypic and functional maturation. These data are in agreement with a previous in vitro study showing that immature NK cell precursors express CD16, NKG2D and KIR only at a late stage of differentiation and also express inhibitory 2B4. Our present study allows a better understanding of the NK cell differentiation in vivo.