Selective depletion of myelin-reactive T cells with the anti-OX-40 antibody ameliorates autoimmune encephalomyelitis

The OX-40 protein was selectively upregulated on encephalitogenic myelin basic protein (MBP)-specific T cells at the site of inflammation during the onset of experimental autoimmune encephalomyelitis (EAE). An OX-40 immunotoxin was used to target and eliminate MBP-specific T cells within the central nervous system without affecting peripheral T cells. When injected in vivo, the OX-40 immunotoxin bound exclusively to myelin-reactive T cells isolated from the CNS, which resulted in amelioration of EAE. Expression of the human OX-40 antigen was also found in peripheral blood of patients with acute graft-versus-host disease and the synovia of patients with rheumatoid arthritis during active disease. The unique expression of the OX-40 molecule may provide a novel therapeutic strategy for eliminating autoreactive CD4+T cells that does not require prior knowledge of the pathogenic autoantigen.

Association of HER2/neu expression with sensitivity to tumor-specific CTL in human ovarian cancer

To study potential sources of tumor-associated Ags in human ovarian cancer, we have established two ovarian tumor cell lines (OvS1 and OvA2) from two ovarian cancer patients, which express the cellular oncogene HER2/neu. Corresponding tumor infiltrating lymphocyte cultures have also been established and display an autologous tumor-specific pattern of cytotoxicity that is HLA-A2 restricted. To determine the potential relationship between HER2/neu expression and CTL-mediated cytolysis, we first established tumor cell clones from OvS1. These were categorized as high or low expressors of HER2/neu (cOvS1+ or cOvS1-, respectively), and cOvS1+ clones displayed a significantly higher sensitivity to CTL killing as compared with cOvS1- clones. To modulate the expression of HER2/neu, ovarian cancer cells were treated with IFN-gamma. After this exposure, HER2/neu expression was significantly decreased, whereas the expression of HLA Class I was significantly increased. Despite the increase in HLA Class I molecules on the cell surface, CTL-mediated cytolysis of both OvS1 and OvA2 was significantly decreased. IFN-gamma treated cOvS1+ clones displayed a similar decrease in sensitivity to CTL killing, whereas IFN-gamma treated cOvS1- clones displayed an increase or no change in sensitivity to CTL. To confirm this apparent association between HER2/neu expression and CTL recognition, melanoma tumor cell lines that were insensitive to ovarian tumor-specific CTL were transfected with the HER2/neu gene. An HLA-A2+ HER2/neu-transfected melanoma cell line was made sensitive to HLA-A2 restricted ovarian tumor-specific CTL but not to HLA-A2 unrestricted CTL, whereas an HLA-A2- HER2/neu-transfected melanoma remained insensitive to HLA-A2 restricted CTL. These results demonstrate that the sensitivity of ovarian epithelial tumor cells to CTL-mediated lysis is associated with the level of expression of HER2/neu, suggesting that this oncogene product may serve as a source of tumor-associated Ags or as an inducer of such peptides. This is the first time in a human tumor system that oncogene expression has been related to the induction of antigenicity. These results prompt us to approach new strategies for immunotherapy of cancer.

Association of HER2/neu expression with sensitivity to tumor-specific CTL in human ovarian cancer

To study potential sources of tumor-associated Ags in human ovarian cancer, we have established two ovarian tumor cell lines (OvS1 and OvA2) from two ovarian cancer patients, which express the cellular oncogene HER2/neu. Corresponding tumor infiltrating lymphocyte cultures have also been established and display an autologous tumor-specific pattern of cytotoxicity that is HLA-A2 restricted. To determine the potential relationship between HER2/neu expression and CTL-mediated cytolysis, we first established tumor cell clones from OvS1. These were categorized as high or low expressors of HER2/neu (cOvS1+ or cOvS1-, respectively), and cOvS1+ clones displayed a significantly higher sensitivity to CTL killing as compared with cOvS1- clones. To modulate the expression of HER2/neu, ovarian cancer cells were treated with IFN-gamma. After this exposure, HER2/neu expression was significantly decreased, whereas the expression of HLA Class I was significantly increased. Despite the increase in HLA Class I molecules on the cell surface, CTL-mediated cytolysis of both OvS1 and OvA2 was significantly decreased. IFN-gamma treated cOvS1+ clones displayed a similar decrease in sensitivity to CTL killing, whereas IFN-gamma treated cOvS1- clones displayed an increase or no change in sensitivity to CTL. To confirm this apparent association between HER2/neu expression and CTL recognition, melanoma tumor cell lines that were insensitive to ovarian tumor-specific CTL were transfected with the HER2/neu gene. An HLA-A2+ HER2/neu-transfected melanoma cell line was made sensitive to HLA-A2 restricted ovarian tumor-specific CTL but not to HLA-A2 unrestricted CTL, whereas an HLA-A2- HER2/neu-transfected melanoma remained insensitive to HLA-A2 restricted CTL. These results demonstrate that the sensitivity of ovarian epithelial tumor cells to CTL-mediated lysis is associated with the level of expression of HER2/neu, suggesting that this oncogene product may serve as a source of tumor-associated Ags or as an inducer of such peptides. This is the first time in a human tumor system that oncogene expression has been related to the induction of antigenicity. These results prompt us to approach new strategies for immunotherapy of cancer.

Expression of epidermal-growth-factor receptor in the K562 cell line by transfection. Altered receptor biochemistry

The epidermal-growth-factor (EGF) receptor was expressed in the human erythroleukaemic cell line K562 by transfection of the receptor cDNA. EGF-receptor biochemistry appears altered in the K562 transfectants. Autophosphorylation of the K562 receptor is not stimulated substantially by EGF. Tyrosine kinase activity of the receptor is high in the absence of EGF, whereas receptor affinity for EGF is low. K562 cells are shown to lack mRNA for transforming growth factor alpha (TGF alpha). Therefore autocrine stimulation of the K562 receptor, at least by TGF alpha, does not explain the observed receptor biochemistry. The K562 receptor is phosphorylated at a single major site in intact cells, a threonine residue that may be Thr-669. Possible mechanisms of regulation of the EGF receptor in the K562 transfectants are discussed.

Characterization of the T cell-mediated cellular cytotoxicity during acute infectious mononucleosis

Primary infection with EBV during acute infectious mononucleosis (IM) is associated with a cytotoxic response against allogeneic target cells. C depletion with anti-CD3 (OKT3) and anti-CD8 (OKT8) mAb decreased the allogeneic cytolysis of two EBV-infected lymphoblastoid cell lines (LCL) by 96% and 89%, respectively. Complement depletion with the NK cell-specific mAb Leu-11b and NKH-1a resulted in only a slight decrease (less than 35%) in the lysis of these LCL. mAb inhibition studies with OKT3 and OKT8 inhibited the allogeneic lysis of two LCL by 87% and 82%, respectively. The alloreactive cytotoxic response was strongly inhibited by mAb specific for MHC class I determinants (W6/32, 65% inhibition and BBM.1, 58% inhibition). Acute IM lymphocytes lysed the allogeneic EBV-negative cell lines HSB2 (45%) and HTLV-1 T cell lines (16%). NK cell-depleted lymphocytes from an acute IM patient demonstrated preferential lysis of K562 transfected with human HLA-A2 (73%) compared with the K562 transfected control (20%). Cold target competition studies with allogeneic and autologous target and competitor LCL demonstrated no significant competitive inhibition between allogeneic and autologous cells. We interpret these results as evidence that 1) the acute IM-alloreactive cytotoxic response is mediated primarily by CTL; 2) these alloreactive CTL lyse allogeneic target cells irrespective of EBV antigenic expression; 3) MHC class I expression is sufficient for allogeneic recognition and lysis of target cells; 4) distinct effector CTL populations mediate lysis of autologous and allogeneic target cells; and 5) during acute IM, EBV infection results in the induction of both virus-specific and alloreactive CTL populations.

Characterization of the T cell-mediated cellular cytotoxicity during acute infectious mononucleosis

Primary infection with EBV during acute infectious mononucleosis (IM) is associated with a cytotoxic response against allogeneic target cells. C depletion with anti-CD3 (OKT3) and anti-CD8 (OKT8) mAb decreased the allogeneic cytolysis of two EBV-infected lymphoblastoid cell lines (LCL) by 96% and 89%, respectively. Complement depletion with the NK cell-specific mAb Leu-11b and NKH-1a resulted in only a slight decrease (less than 35%) in the lysis of these LCL. mAb inhibition studies with OKT3 and OKT8 inhibited the allogeneic lysis of two LCL by 87% and 82%, respectively. The alloreactive cytotoxic response was strongly inhibited by mAb specific for MHC class I determinants (W6/32, 65% inhibition and BBM.1, 58% inhibition). Acute IM lymphocytes lysed the allogeneic EBV-negative cell lines HSB2 (45%) and HTLV-1 T cell lines (16%). NK cell-depleted lymphocytes from an acute IM patient demonstrated preferential lysis of K562 transfected with human HLA-A2 (73%) compared with the K562 transfected control (20%). Cold target competition studies with allogeneic and autologous target and competitor LCL demonstrated no significant competitive inhibition between allogeneic and autologous cells. We interpret these results as evidence that 1) the acute IM-alloreactive cytotoxic response is mediated primarily by CTL; 2) these alloreactive CTL lyse allogeneic target cells irrespective of EBV antigenic expression; 3) MHC class I expression is sufficient for allogeneic recognition and lysis of target cells; 4) distinct effector CTL populations mediate lysis of autologous and allogeneic target cells; and 5) during acute IM, EBV infection results in the induction of both virus-specific and alloreactive CTL populations.

Regulation of cytotoxic T lymphocyte-mediated graft rejection following bone marrow transplantation

Cytotoxic T lymphocytes have been implicated as the effector cell mediating graft rejection following human allogeneic bone marrow transplantation. We have studied a BMT patient who rejected haploidentical T cell-depleted marrow. In vitro studies demonstrated that the circulating lymphocytes were CD3+ and CD8+, of recipient origin, and exhibited selective cytotoxicity against donor-specific class I major histocompatibility complex antigens. Cytotoxicity was inhibited by monoclonal antibodies directed against CD3, CD8, CD2, and lymphocyte function-associated antigen-1 on the T cell, and against MHC class I proteins on the target cell. Furthermore, these circulating cells inhibited the in vitro growth and differentiation of enriched donor bone marrow progenitor cells, an inhibition that was partially reversed by anti-CD3 MAb. Donor-specific recipient-derived CTL may mediate resistance to engraftment, and CTL activity may be inhibited by a number of MAb. The implications of these findings for host preparation and treatment are discussed.

Recognition of interspecies hybrid class I histocompatibility antigens by antigen-specific cytolytic T lymphocytes

Two reciprocal interspecies hybrid class I histocompatibility genes have been constructed between genomic clones of human HLA-A2 and murine H-2Kb. The proteins encoded by these genes have been designated A21+2/Kb, where the polymorphic domains, alpha 1 and alpha 2, of HLA-A2 are linked to the carboxyl-terminal domains (alpha 3, transmembrane, and intracytoplasmic domains) of H-2Kb, and Kb1+2/A2, where the alpha 1 and alpha 2 domains of the H-2Kb antigen are linked to the carboxyl-terminal domains of HLA-A2. These genes have been transfected and expressed in recipient mouse L cells and human RD (rhabdomyosarcoma) cells. Both hybrid antigens were found to be serologically intact when tested with a panel of antigen-specific monoclonal antibodies. The monoclonal antibody W6/32, which recognizes a monomorphic determinant on all HLA-A, -B, and -C antigens, recognizes the alpha 1 and/or the alpha 2 domain, rather than the more conserved alpha 3 domain. Human cytolytic T lymphocytes (CTL) specific for the HLA-A2 antigen recognized the A2 and A21+2/Kb proteins only when expressed in human cells and not when expressed in mouse cells, even when surface antigen levels were 10-fold greater on the mouse cells than on the human cells. In contrast, a long-term, murine anti-H-2b CTL line not only lysed mouse L-cell lines that expressed the parental Kb and hybrid Kb1+2/A2 antigens but also lysed the Kb and Kb1+2/A2 human cell RD transformants as well. In both cases, the level of CTL recognition and lysis of the transformants that expressed the native antigen Kb was greater than of those transformants that expressed the hybrid antigen Kb1+2/A2. These data suggest that the carboxyl-terminal domains play some role in CTL allorecognition. The lack of human CTL recognition of HLA molecules expressed in mouse L cells, however, cannot be explained by the presence of a xenogeneic carboxyl terminus. Since murine CTL can recognize their target antigen when expressed on the surface of human cells, the possibility remains either that a ligand necessary for other molecular interactions of human CTL may be absent on mouse target cells or that murine and human CTL differ in affinity of binding to target antigens in the absence of accessory-molecule interactions.

beta 2-Microglobulin from serum associates with several class I antigens expressed on the surface of mouse L-cells

Bovine beta 2-microglobulin (beta 2-m) present in fetal calf serum (FCS) is able to replace endogenous beta 2-m associated with several class I antigens from human and mouse cells maintained in culture [Bernabeu et al. (1984) Nature, Lond. 308, 642-645]. Here we show that human HLA-A2 and HLA-B7, as well as mouse H-2Ld and H-2Dd heavy chains expressed after gene transfer in mouse L-cells, associate to a large extent with bovine beta 2-m. We also demonstrate that bovine beta 2-m associated with the endogenous H-2Kk/Dk heavy chains generates an antibody response when L-cells are injected into syngeneic C3H mice.

Coexpression of the human HLA-A2 or HLA-B7 heavy chain gene and human beta 2-microglobulin gene in L cells

L cells expressing human HLA-A2 or HLA-B7 class I antigen heavy chains are not recognized by human cytotoxic T lymphocytes directed at HLA-A2 or HLA-B7 antigens. To test whether the absence of human beta 2-m was the cause of the lack of recognition by the human cytotoxic T lymphocytes, coexpression of the human beta 2-m gene and the HLA-A2 or HLA-B7 heavy chain in L cells ("double transfectants") was obtained. In addition, L cells expressing HLA-A2 or HLA-B7 antigens in association with human beta 2-m were obtained by an exchange reaction, in which human beta 2-m from serum replaced the endogenous murine beta 2-m. Both types of transfectant cells were used in 51Cr-release assays and cold target inhibition assays for human cytotoxic T cell clones which were directed at HLA-A2 or HLA-B7. Neither human CTL clones nor a mixture of CTL specific for HLA-A2 and HLA-B7 were able to recognize these cells. Several alternative explanations for these observations are discussed.

Coexpression of the human HLA-A2 or HLA-B7 heavy chain gene and human beta 2-microglobulin gene in L cells

L cells expressing human HLA-A2 or HLA-B7 class I antigen heavy chains are not recognized by human cytotoxic T lymphocytes directed at HLA-A2 or HLA-B7 antigens. To test whether the absence of human beta 2-m was the cause of the lack of recognition by the human cytotoxic T lymphocytes, coexpression of the human beta 2-m gene and the HLA-A2 or HLA-B7 heavy chain in L cells ("double transfectants") was obtained. In addition, L cells expressing HLA-A2 or HLA-B7 antigens in association with human beta 2-m were obtained by an exchange reaction, in which human beta 2-m from serum replaced the endogenous murine beta 2-m. Both types of transfectant cells were used in 51Cr-release assays and cold target inhibition assays for human cytotoxic T cell clones which were directed at HLA-A2 or HLA-B7. Neither human CTL clones nor a mixture of CTL specific for HLA-A2 and HLA-B7 were able to recognize these cells. Several alternative explanations for these observations are discussed.

Thymectomized, irradiated, and bone marrow-reconstituted chimeras have normal cytolytic T lymphocyte precursors but a defect in lymphokine production

A model system has been developed to study extrathymic T cell differentiation; mice have been thymectomized, lethally irradiated, and reconstituted with bone marrow cells depleted of Thy-1+ cells. After 8 wk, the spleen cells of these athymic, bone marrow-reconstituted chimeras contain Thy-1+ precytolytic T lymphocytes (CTL) that are able to respond to antigen only if supernatant from Con A-activated T cells is added to culture. The phenotype of these pre-CTL is similar to that of thymocytes, suggesting that they may be immature T cells. Initial evaluation of the CTL repertoire of these athymic mice demonstrated that the CTL generated to trinitrophenyl-modified syngeneic cells are H-2-restricted, and that the CTL generated to alloantigens have many of the cross-reactivities observed in normal mice but not in nude mice. In this report, we demonstrate a helper T cell defect in these thymectomized chimeras. These chimeras lack an Ly-1+ helper cell required for thymocytes to differentiate to CTL. Further studies revealed that when spleen cells from these thymectomized chimeras were stimulated with Con A, they produced normal levels of interleukin 2. However, these splenocytes were defective in the production of another factor needed for CTL differentiation.

Thymectomized, irradiated, and bone marrow-reconstituted chimeras have normal cytolytic T lymphocyte precursors but a defect in lymphokine production

A model system has been developed to study extrathymic T cell differentiation; mice have been thymectomized, lethally irradiated, and reconstituted with bone marrow cells depleted of Thy-1+ cells. After 8 wk, the spleen cells of these athymic, bone marrow-reconstituted chimeras contain Thy-1+ precytolytic T lymphocytes (CTL) that are able to respond to antigen only if supernatant from Con A-activated T cells is added to culture. The phenotype of these pre-CTL is similar to that of thymocytes, suggesting that they may be immature T cells. Initial evaluation of the CTL repertoire of these athymic mice demonstrated that the CTL generated to trinitrophenyl-modified syngeneic cells are H-2-restricted, and that the CTL generated to alloantigens have many of the cross-reactivities observed in normal mice but not in nude mice. In this report, we demonstrate a helper T cell defect in these thymectomized chimeras. These chimeras lack an Ly-1+ helper cell required for thymocytes to differentiate to CTL. Further studies revealed that when spleen cells from these thymectomized chimeras were stimulated with Con A, they produced normal levels of interleukin 2. However, these splenocytes were defective in the production of another factor needed for CTL differentiation.