T-cell leukemogenesis is an inappropriate lineage decision-making process: implications for precision oncology

Genetic lineage tracing in cell type-specific mouse models of T-cell acute lymphoblastic leukemia (T-ALL) have revealed that tumor cell identity is imposed by expression of the oncogene Lim Domain Only 2 (LMO2), rather than by the target cell phenotype. This approach allowed to identify that secondary genomic alterations, like Notch1 mutations, appeared late and only took place within the thymus during T-ALL development. These concepts are therefore critical for the development of modern therapies aimed at curing T-ALL.

CD8(+) T cell-mediated injury in vivo progresses in the absence of effector T cells

Tissue injury is a common sequela of acute virus infection localized to a specific organ such as the lung. Tissue injury is an immediate consequence of infection with lytic viruses. It can also result from the direct destruction of infected cells by effector CD8(+) T lymphocytes and indirectly through the action of the T cell-derived proinflammatory cytokines and recruited inflammatory cells on infected and uninfected tissue. We have examined CD8(+) T cell-mediated pulmonary injury in a transgenic model in which adoptively transferred, virus-specific cytotoxic T lymphocytes (CTLs) produce lethal, progressive pulmonary injury in recipient mice expressing the viral target transgene exclusively in the lungs. We have found that over the 4-5 day course of the development of lethal pulmonary injury, the effector CTLs, while necessary for the induction of injury, are present only transiently (24-48 h) in the lung. We provide evidence that the target of the antiviral CD8(+) T cells, the transgene expressing type II alveolar cells, are not immediately destroyed by the effector T cells. Rather, after T cell-target interaction, the type II alveolar cells are stimulated to produce the chemokine monocyte chemoattractant protein 1. These results reinforce the concept that, in vivo, the cellular targets of specific CTLs may participate directly in the development of progressive tissue injury by activating in response to interaction with the T cells and producing proinflammatory mediators without sustained in vivo activation of CD8(+) T cell effectors.

Sensitization of resting T cells to autologous natural-killer-cell-mediated lysis by phytohemagglutinin

Natural killer (NK) cells are non-T, non-B cell lymphocytes that lyse a variety of tumor and virus-infected cells. In this study, we demonstrated that phytohemagglutinin (PHA) rendered resistant autologous T cells extremely sensitive to natural-killer(NK)-cell-mediated lysis. The sensitization was very rapid and concentration-dependent (0.01-1 microg/ml); 62% and 95% of autologous T cells were lysed by interleukin-2-activated NK cells 5 min and 18 h respectively after treatment with PHA (1 microg/ml). The maximal decrease in the level of MHC class I molecules observed on T cells was 22%. Induction of susceptibility to NK-mediated lysis was correlated with the expression of activation markers on T cells treated for relatively long intervals (more than 18 h) with high concentrations of PHA (more than 0.1 microg/ml). Sensitization of T cells required RNA and protein synthesis, although DNA synthesis was not essential. We propose that this unique system is suitable for studying the mechanisms involved in recognition and killing of target cells by NK cells.

A strategy for evaluating lymphokine activation and novel monoclonal antibodies in antibody-dependent cell-mediated cytotoxicity and effector cell retargeting assays

As novel antibody therapeutics are developed for different malignancies and require evaluation with cells previously uncharacterized as antibody-dependent cell-mediated cytotoxicity (ADCC) targets, efficient description of key parameters of the assay system expedites the preclinical assessment. A strategy is presented to define the behavior of cell lines or cell cultures as targets in ADCC assays, with emphasis on cytokine activation of effectors and attention to contributions of natural killer cells. Features of the target cell, the effector cell, and the assay itself are separately assessed. Target cells are evaluated for the kinetics of chromium labelling and release, and positive and negative control antibodies are selected. Effector cells are evaluated in ADCC for the impact of different donor sources, storage conditions, lymphokine concentration and duration of activation. The assay itself is assessed for the impact of the type of liquid medium, incubation duration, and effector-to-target ratio. Representative data are presented with a model human malignant T cell line, HuT102.

Phototoxic liposomes coupled to an antibody that alone cannot modulate its cell-surface antigen kill selected target cells

Molecules such as antibodies that bind to cell surfaces can be used to deliver cytotoxic drugs to selected cells. To be effective the drug must usually be taken into the cells by endocytosis. In this study a T-cell line (CCRF-CEM) was effectively killed by liposomes carrying a photosensitizer and bearing the antibody OKT4 (anti-CD4). The unconjugated antibody does not induce antigenic modulation in the target cells, an indication of the absence of endocytosis, and would therefore not normally have been selected as an agent for drug delivery. It cannot, however, be concluded with certainty that the conjugates act at the cell surface and several alternative explanations of their efficacy are offered.

Lysis by interleukin 2-stimulated tumor-infiltrating lymphocytes of autologous and allogeneic tumor target cells

Peripheral blood lymphocytes (PBL) and tumor-infiltrating lymphocytes (TIL) were isolated from six cancer patients and cultured in the presence of 100 units/ml of recombinant interleukin 2 (IL2). Both IL2-stimulated PBL (IL2-PBL) and IL2-stimulated TIL (IL2-TIL) lysed fresh and short-term cultured autologous tumor cells in four and six cases, respectively. In four out of six patients IL2-TIL showed a slightly higher tumor cytotoxicity than IL2-PBL without lysing autologous normal PBL or TIL. Like IL2-PBL, IL2-TIL also killed allogeneic fresh and cultured targets of different histotypes, suggesting a lack of autologous tumor cytotoxic specificity. TIL cultured for 3 weeks in IL2 maintained their killing activity against autologous and allogeneic tumor targets. Phenotypic analysis of uncultured TIL showed a predominance of CD3+ T cells (approximately 70%) with CD4+ (approximately 60%) and CD8+ (20%) lymphocyte subsets, whereas less than or equal to 3% of CD16+ natural killer cells were present. TIL but not PBL contained 12%-19% of lymphocytes which expressed activation markers such as DR and TAC. The culture of both TIL and PBL in IL2 for 2-3 weeks induced an increase in the percentage of CD8+ and a decrease in CD4+ and augmentation of Leu 19+, DR+, and TAC+ cells. These results indicate that IL2-TIL can lyse autologous tumor cells slightly better than IL2-PBL, although such an effect was also evident against allogeneic neoplastic targets.

Granulocyte-monocyte-colony-stimulating factor augments the cytotoxic capacity of lymphocytes and monocytes in antibody-dependent cellular cytotoxicity

Human peripheral blood mononuclear cells (lymphocytes and monocytes) were preincubated for 0-24 h with human recombinant granulocyte-monocyte-colony-stimulating factor (GM-CSF) and used as effector cells in an 18 h antibody-dependent cellular cytotoxicity (ADCC) assay with SW948 (a human colorectal carcinoma cell line) as target cells and mAb 17-1A. A significant increase in the lytic capability was noted after 0.5-2 h of preactivation while longer preincubation times did not significantly increase the lytic potential. GM-CSF at 0.01 microgram/ml induced the best tumor cell lysis while higher concentrations were inhibitory. GM-CSF pretreatment induced a statistically significant increase in the lytic capacity of both monocytes and lymphocytes in ADCC as well as in the spontaneous cytotoxicity.

MHC nonrestricted cytotoxic T cell clones with selective specificity from patients with transitional cell carcinoma (TCC) of the urinary bladder

Lymphocytes from patients with transitional cell carcinoma (TCC) of the urinary bladder are more cytotoxic to bladder tumor cells than to a variety of control cells. This disease-related cytotoxicity has previously been shown to involve several mechanisms and different types of effector cells. To analyze further the nature of the effector cells operative in this system, peripheral blood lymphocytes from eight TCC patients were stimulated in vitro with TCC extract and cultured in the presence of interleukin 2 and allogeneic feeder cells. When tested for cytotoxicity in vitro on a target cell panel including both adherent and nonadherent cell lines, the lymphocytes killed a broad spectrum of targets in a major histocompatibility complex (MHC)-unrestricted fashion. When cloned by limiting dilution, clones were obtained which displayed a more restricted pattern of target cell killing. Some of the clones were highly but not exclusively selective for TCC-derived target cells. Phenotypically, these cells resembled mature T cells of CTL-type (CD8+/CD4-). They also expressed the CD3/5 T cell antigen receptor complex but target cell killing was not MHC-restricted. The results of various inhibition experiments suggested that the CD3/TCR complex was involved in the cytotoxicity exhibited by these effector cells. However, its precise role in target cell recognition and the identification of the tumor cell structures recognised by the effector cells require further studies.

In vitro activity of R 61837, a new antirhinovirus compound

R 61837 or 3-methoxy-6-[4-(3-methylphenyl)-1-piperazinyl]pyridazine is a new and potent inhibitor of rhinoviruses at concentrations not inhibitory to HeLa cell growth. Different rhinovirus serotypes varied widely in their susceptibility to the antiviral agent. The MICs for 50% CPE reduction ranged from 0.004 to 15 micrograms/ml. The yields of the most susceptible serotypes were reduced by a factor of 1,000 to 10,000 after single round high multiplicity infections in presence of low concentrations of the compound. The inactivation of some but not all serotypes in a time-, concentration- and temperature-dependent way by R 61837 indicated a direct interaction between the drug and the viral particles. The antiviral activity of the compound was confirmed in the human target cells for rhinoviruses by experiments using nasal polyp explant cultures.

Autologous antibodies to human bladder cancer

The autologous serologic reactivity of 13 patients with bladder cancer was evaluated using cell lines derived from each individual's own tumor as targets. Protein A and immune adherence assays were employed to determine antibody binding to the tumor targets at varying passage numbers. Autologous reactivity was found in 6 of the 13 cell lines tested. However, the titer was usually low regardless of the passage number. Seven autologous serum/cell line combinations were tested using both low and high passage cells as targets. In six of these combinations, the degree of antibody binding was similar with both low and high passage target cells. The incidence of autologous reactivity in the 12 patients with urothelial tumors was 50%.

Monocyte-mediated drug-dependent cellular cytotoxicity: effects on different WEHI 164 target cell lines

The contribution of monocyte cytotoxic protein factor (CF) to monocyte-mediated drug-dependent cellular cytotoxicity (DDCC) has been investigated. Cell lines which have been derived from murine WEHI 164 cells (termed WEHI 164 parental) by selecting for high (WEHI 164 clone 3) and low (R-WEHI 164) sensitivity to CF-mediated cytotoxicity were used as target cells in DDCC. By comparing the CF doses which produced 50% dead cells (LD 50) we found that WEHI 164 clone 3 was approximately 30 times more sensitive than WEHI 164 parental which in turn was 70 times more sensitive than R-WEHI 164. Actinomycin D (Act D) treatment of WEHI 164 parental and R-WEHI 164 greatly increase susceptibility to CF-mediated cytotoxicity. The susceptibility of WEHI 164 clone 3 was apparently somewhat increased at low dilutions of CF, whereas no significant increase was observed at high dilutions. The susceptibility to DDCC of the three target cell lines (WEHI 164 parental, WEHI 164 clone 3, and R-WEHI 164) correlated with the sensitivity pattern obtained in CF-mediated cytotoxicity of Act D-treated target cells. Monocyte- and CF-mediated cytotoxicity against Act D-treated WEHI 164 clone 3 and R-WEHI 164 was inhibited by neutralizing CF antiserum. These data indicate that CF is an effector molecule in monocyte-mediated DDCC.

Analysis of the cellular immune response to and adoptive immunotherapy of a BALB/c lymphoma that cross-reacts with normal DBA/2 cells

We have previously shown that YC8, a Moloney virus-induced BALB/c lymphoma, is susceptible to lysis by BALB/c anti-DBA/2 effector cells. To further evaluate the relationship between non-H-2 antigens of DBA/2 background and tumor-associated determinants, we investigated the pattern of cytotoxic and proliferative responses induced in BALB/c mice by immunization with YC8 lymphoma. Spleen cells from tumor-immunized animals were restimulated in vitro with YC8 cells and tested for cytotoxicity on target cells of different strains and haplotypes. Cytotoxicity was observed only against YC8, DBA/2 blasts, and P815 (a DBA/2 mastocytoma). BALB/c anti-YC8 effectors were equally blocked by unlabeled YC8 and P815 cells when assayed on YC8 labeled targets. A clonal analysis, however, revealed the existence of at least two types of effectors, one lytic for both P815 and YC8 cells, the other lytic for YC8 cells only. BALB/c anti-YC8 cells proliferate when stimulated both with YC8 and DBA/2 cells in the presence of accessory cells. When tested in an adoptive transfer assay, anti-YC8 cells given i.v. cured 100% of i.v. and 75% of i.p. tumor-injected mice, respectively. When given i.p. anti-YC8 effectors cured 100% of i.p. tumor-injected animals. These results confirm the expression of non-H-2, DBA/2-like antigens on the BALB/c lymphoma YC8 and reveal the presence of additional tumor-associated determinants; both sets of antigens may induce a cellular immune response and elicit immune lymphocytes which can eradicate YC8 cells in an adoptive immunotherapy assay.

A microassay for the rapid and selective binding of cells from solid tumors to mouse macrophages

A microassay was developed to study the rapid binding characteristics of murine macrophages activated by gamma interferon and muramyl dipeptide to adherent neoplastic or nonneoplastic target cells. The binding of tumor cells to both activated and nonactivated macrophages was time- and temperature-dependent, and independent of tumor cell type. Activated macrophages bound more tumor cells than nonactivated macrophages. The initial binding of macrophages to target cells did not necessarily lead to lysis. First, primed macrophages bound tumor cells but did not lyse them, and second, nonactivated macrophages bound nontumorigenic cells without subsequent lysis. The rapid binding assay described here could prove useful in investigating the recognition mechanism(s) between macrophages and tumor cells derived from solid primary and metastatic cancers.

In vivo immunization against autologous glioblastoma-associated antigens

A glioblastoma patient was immunized in vivo with a mixture of autologous and homologous glioblastoma cells coupled to adjuvant peptide and cord-factor analog. Immune activity of peripheral blood lymphocytes was measured in a short-term 51chromium-release assay against autologous tumor target cells. The patient developed direct cell-mediated cytotoxicity against tumor-associated antigens, which appeared to be T-cell mediated.

A 3-dimensional tumor growth inhibition assay for testing monoclonal antibody cytotoxicity

A 3-dimensional tumor growth inhibition assay [18] has been adapted to test the cytotoxic activity of a panel of monoclonal antibodies directed to various antigenic determinants on the surface of mouse mammary tumor cells. Target cells can be prepared from either cultured cells or from pieces of fresh tumor. Antibody and complement are added when cells are growing actively and cell growth can be measured, non destructively, over a 7-10-day period. Effective diffusion of antibody through collagen gel and binding to target cells embedded in the gel is demonstrated by indirect immunofluorescent staining. The specificity of monoclonal antibody AMT 101 cytotoxicity for mouse mammary tumor cells is the same in trypan blue exclusion assays of single-cell suspensions as in collagen gel assays, with complete killing seen in the collagen gel assay only. The collagen gel assay allows the testing of repeated treatments in vitro, as well as combined treatment with multiple antibodies. It also allows cell-cell interaction and preserves all cell components in the tumor. The collagen gel assay has potential as a method of predicting the outcome of monoclonal antibody treatment of solid tumors.

Deficient expression of class-I HLA in some cases of acute leukemia

Leukemic cells from the blood and marrow of 25 cases of newly diagnosed acute leukemia were presented as target cells to alloreactive effector cells from unrelated normal donors in cell-mediated cytotoxicity assays. In three cases the leukemic targets were poorly killed relative to nonleukemic, HLA-identical target cells. The poor killing of the leukemic cells from one of these cases was shown by competitive inhibition to be due to deficient expression of normal class-I HLA antigens rather than resistance to lysis. Furthermore, the leukemic cells from these three patients were also deficient in binding monoclonal antibodies to nonpolymorphic determinants of class-I HLA and B2 microglobulin. Two additional cases were identified as having a less extensive deficit of HLA, and may be representative of a group with relatively subtle changes in these cell surface antigens. The possible significance of reduced expression of HLA in leukemic progression and in susceptibility to graft-vs-leukemia reactions after bone marrow transplantation is discussed.

Cell-mediated immune reaction against BK virus-transformed cells

Syngeneic or allogeneic cells transformed by BK virus (BKV) were used to immunize C57BL/6J mice. After in vitro stimulation, lymphocytes prepared from the spleens of immunized mice were used in in vitro cytotoxicity tests. The results of these tests revealed the presence of a cell surface antigen, presumably corresponding to the viral transplantation antigen, common to all tested BKV- and SV40-transformed cell lines of C57BL/6J origin. An allogeneic cell line transformed by BKV also contained the same antigen. Immunization, i.e., in vivo priming, did not require syngeneic transformed cells, whereas cytolysis was only observed when the virus-specific antigen on target cells was associated with the same H2 haplotype as was expressed by effector cells. An additional unidentified antigen was shared by some of the BKV-transformed cell lines and cell lines transformed by simian adenovirus SA7.

Antibodies to tumour eluates react preferentially with non-lymphoid tumours

Rabbit antisera raised against eluates from a murine fibrosarcoma were characterised using a 125I-protein A assay and a wide variety of target cells. The sera bound preferentially to rodent tumours of non-lymphoid origin, whereas monkey and human cells did not react. Murine lymphoid cells and macrophages (normal or transformed) and normal liver and kidney cells all bound low amounts of the antibody, while embryonic cells were intermediate in reactivity. Target cell treatments indicated that the surface antigens being detected were sensitive to proteolysis and calcium depletion. In addition actively growing cells bound more antibody than resting cells. Double binding assays with sera specific for plasma membrane components suggested the eluate antigens may play a structural role. Immunofluorescent studies demonstrated that surface antigens detected by the antisera capped and were lost and this was followed by synthesis and surface re-expression. Sera such as these, which can distinguish between normal and malignant cells in the rodent, have obvious applications in many aspects of tumour-related investigations.

A 125I-protein A-binding assay detecting antibodies to cell surface antigens. Evidence for the presence of specific antibodies against leukemia-associated antigens in human leukemias

A 125I-protein A-binding assay detecting antibodies to cell surface antigens on human blood cells was developed and evaluated using sera from multitransfused nonleukemic patients sensitized against HLA antigens. The binding assay was found to be reproducible and more sensitive than conventional HLA testing. Seven patients with acute myelogenous leukemia and two patients with acute lymphoblastic leukemia successfully treated by chemotherapy were then investigated. Sera from seven of the patients studied in partial or complete remission demonstrated significant binding to autochthonous leukemic cells obtained from bone marrow or peripheral blood. In two cases sera taken during the leukemic stage demonstrated the most pronounced binding to the patients' own leukemic cells. Sera from four patients with demonstrable significant binding to autochthonous leukemic cells failed to bind to autochthonous remission cells when both types of target cells were tested in parallel. Differences in serum concentrations of IgG, IgA, and IgM were not the cause of the demonstrated increased binding of leukemic sera to autochthonous target cells. We propose that the 125I-protein A-binding assay presented in this paper detects antibodies reacting selectively with acute leukemia cells.

Human spontaneous lymphocyte-mediated cytotoxicity (SLMC) against malignant and normal tissue-derived target cell lines tested in autologous and allogeneic combinations by the microcytotoxicity assay

Effector cell types and effector mechanisms of human spontaneous lymphocyte-mediated cytotoxicity (SLMC) were studied in a 44-h microcytotoxicity titration assay. Peripheral blood lymphocytes from cancer patients and controls were used as effector cells either unfractionated or after fractionation by rosetting techniques or affinity chromatography. The possible immunoglobulin dependency of the reactions was studied by incorporation of specific Fab fragments of rabbit anti-human IgG antibodies in the incubation mixtures. Twelve different target cell lines of either high or low sensitivity to SLMC and with or without easily detectable HLA antigens were used. Most of the target cells were cell lines derived from transitional cell carcinoma of the urinary bladder (TCC). Both allogeneic and autologous lymphocyte target cell combinations were tested. Although high- and low-sensitivity target cells differed significantly in susceptibility to lysis, the predominating SLMC was displayed by Fc-receptor-positive lymphocytes in both allogeneic and autologous combinations. Addition of the Fab anti-immunoglobulin reagent to the incubation mixtures resulted in strong inhibition of cytotoxicity regardless of the type of target cells used and in allogeneic as well as in autologous lymphocyte target cell mixtures. However, in some combinations no inhibition was seen and inhibition was usually not complete, suggesting that both immunoglobulin-dependent (i.e., ADCC-like) and immunoglobulin-independent mechanisms were involved in the cytotoxicity reactions. The results of the microcytotoxicity assay were compared with those obtained with aliquots of the same lymphocytes and target cells in an 18-h 51Cr-release assay. While similar results were obtained with high-sensitivity target cells, with low-sensitivity targets and in some autologous combinations the two assay systems registered lymphocyte/target cell interactions which differed with regard to specificity, effector cell type, and immunoglobulin dependency.

Production of a tumor-specific xenoantiserum from partially purified immunoprotective tumor antigen

Rabbits immunized with the immunoprotective TSTA fraction partially purified by preparative isoelectric focusing of 3 M KCl extracts from a chemically induced murine sarcoma, MCA-F, produced specific xenoantisera as assessed by an indirect membrane immunofluorescence assay. Only the immunizing tumor, MCA-F, and not the antigenically distinct MCA-D or MCA-T target cells were stained by the xenoantiserum. Absorption of anti-MCA-F antiserum with the antigenically distinct MCA-D or MCA-T cells did not reduce its capacity to bind to MCA-F cells. The immunofluorescence reaction was competitively inhibited by MCA-F fractions that induced specific immunoprotection: crude 3 M KCl extract, isoelectrically focused TSTA (fraction 15), and intact irradiated MCA-F cells. The TSTA specificity of these xenoantisera suggests that they may provide useful reagents for rapid isolation and characterization of the immunoprotective moiety.

Regulation of human natural killing by levamisole

The effect of levamisole on human natural killing (NK) has been studied. In short-term chromium release assays, levamisole at a concentration of 10(-3) M was inhibitory to NK when present in the assays. Pretreatment of NK effector cells and K562 target cells with levamisole separately indicated that the effect was on effector cell activity and was not due to any change in target cell susceptibility. Inactivation of the effector cells required greater than 4 h pretreatment with levamisole if NK activity was subsequently tested in the absence of the drug. Pretreatment with levamisole for up to 19 h had no effect on the lymphocyte proliferative response to phytohemagglutinin (PHA). NK activity of drug-inactivated effector cells recovered after further incubation in levamisole-free medium. Levamisole at 10(-4) M or less had no effect on NK either by pretreatment or by its presence in the NK assays.

The immunopathogenesis of chronic HBV induced liver disease

In conclusion, until the cellular biology of hepatitis B virus infection is understood and until the technology for the development of suitable virus infected autologous target cells is available, it will not be possible to definitively establish the mechanism involved in the pathogenesis of hepatitis B virus induced hepatocellular injury. Clearly, considerable effort must now be focused on the basic biology of virus infection, replication, and effects on hepatocellular metabolism before it will be possible to perform the definitive experiments to elucidate the role played by the immune system in the pathogenesis of this disease.