Human Alloreactive CTL Interactions with Gliomas and with Those Having Upregulated HLA Expression from Exogenous IFN-γ or IFN-γ Gene Modification

Abstract

By flow cytometry, a panel of 18 primary glioma cell explants exhibited high expression of class I HLA-A, B, C, but class II HLA-DR expression was absent. Freshly isolated normal brain cells displayed little or no HLA antigens. Alloreactive cytotoxic T lymphocytes (aCTL), sensitized to the HLA of the patient, were generated in a one-way mixed lymphocyte response (MLR). The specificity of aCTL was confirmed to be to target cells (patient glioma cells or lymphoblasts) expressing the relevant HLA antigens. However, nontumor patient-specific aCTL did not lyse normal brain cells. Titration of antibodies to HLA class I into cytotoxicity assays blocked lysis of gliomas by aCTL, confirming aCTL T cell receptor (TCR) interactions with the class I antigen on gliomas. Furthermore, aCTL interactions with glioma cells caused their apoptosis. Coincubations of aCTL with gliomas resulted in upregulated cytokine secretion. Importantly, dexamethasone, an immunosuppressive steroid used for brain edema, did not affect aCTL lytic function against tumor, indicating that steroid-dependent patients may benefit from the immunotherapy. We also explored the use of interferon-gamma (IFN-gamma) to increase aCTL tumor recognition. Coincubation of gliomas with exogenous IFN-gamma (500 U/ml, 48 h) caused a 3-fold upregulation of HLA class I and a slight induction of class II antigen expression. Gene-modified glioma cells producing IFN-gamma similarly displayed upregulated HLA expression. Glioma cells incubated with exogenous IFN-gamma or IFN-gamma-transduced glioma cells were more susceptible to lysis by aCTL than their parental counterparts, thus supporting the concept of combining IFN-gamma cytokine gene therapy with adoptive aCTL immunotherapy for brain tumor treatment.

γδ T cells as immune effectors against high-grade gliomas

“…Placement of unrelated allogeneic T lymphocytes into the tumor bed has produced isolated cases of prolonged remission. However, a significant survival benefit has not been shown, and the success of therapy was found to be highly dependent on the degree of MHC Class I expression of the individual tumor [7,27].…”

“…Immunotherapy is an attractive approach, but the unique nature of the brain's microenvironment and the immunosuppressive properties of glioblastoma multiforme (GBM) tumors present a substantial challenge to the deployment of this line of therapy [2][3][4][5]. Requirements for initiation of immune responses in the brain are more stringent due to relative isolation from the systemic circulation [6], poor expression of HLA antigens on brain cells [7], and unconventional lymphatic drainage [2]. …”

Glioma Cells Display Complex Cell Surface Topographies That Resist the Actions of Cytolytic Effector Lymphocytes

“…The known requirements for initiation of immune responses in the brain are more stringent than those cancers found elsewhere in the body because of the relative isolation from the systemic circulation via the blood-brain barrier (9), poor expression of HLA Ags on brain cells (10), and unconventional lymphatic drainage (11). Local microglial cells can process and present tumorassociated Ags to CTL (12)(13)(14).…”

Immunizations With IFNγ Secreting Tumor Cells can Eliminate Fully Established and Invasive Rat Gliomas

“…27,28 However, the base-line levels of MHC class I in the healthy central nervous system, unlike other tissues, are very low or undetectable. 29,30 Interestingly, primary human glioma cell explants and frozen glioblastoma tissue samples have been shown to stain positively for MHC class I. 30,31 In this context it is noteworthy that N29 cells expressed very low levels of MHC I, whereas N32 cells expressed higher levels.…”

“…29,30 Interestingly, primary human glioma cell explants and frozen glioblastoma tissue samples have been shown to stain positively for MHC class I. 30,31 In this context it is noteworthy that N29 cells expressed very low levels of MHC I, whereas N32 cells expressed higher levels. Whether this is linked to the more invasive growth of N29 tumors is yet to be investigated.…”