Possibility of detecting human embryonal leukemia antigen]

A possibility of detecting embryonic leukemic antigen on human leukemic blast cells in an acute human leukemia cytotoxicity test with the sera and 7S and 19S serum immunoglobulins of the placental blood was studied. The presence on the blast cells of patients suffering from acute leukemia of an antigen detectable by antibodies of placental blood (of parturients) was demonstrated; this antigen was absent on the leukocytes of healthy donors.     

Enzyme-linked immunosorbent assay in screening of leukemia-associated nuclear proteins

Our previous data revealed some diversities in electrophoretic characteristics of nuclear fraction proteins isolated from peripheral blood mononuclear cells of B-cell chronic lymphocytic leukemia (B-CLL) patients and healthy donors. Two electrophoretically-specific nuclear non-histones in the molecular mass zone of 38/39 and 44/46 kDa of leukemic mononuclear cells were used as immunogens to produce rabbit antisera. The Western blot analysis indicated that both nuclear components are expressed only in mononuclear cells isolated from peripheral blood of B-CLL patients, but not in those isolated from the blood of healthy donors. For further investigations of nuclear fraction from normal and B-CLL mononuclear cells, an enzyme-linked immunosorbent assay (ELISA) was used. The results obtained by ELISA with the antisera raised against both electrophoretically-specific B-CLL nuclear polypeptides revealed a different extend of cross-reactivity of nuclear fraction preparations isolated from normal cells and those isolated from leukemic ones. We noticed that nuclear fraction preparations which originated from leukemic mononuclear cells are much more reactive than normal ones with both antisera (at a broad range of antisera dilutions).     

Reactivity of B leukemic lymphocytes of patients with chronic lymphocytic leukemia to PWM and PHA

The ability of leukemic B lymphocytes to proliferate after in vitro stimulation with PWM and PHA was studied in 15 patients with chronic lymphocytic leukemia. Peripheral blood lymphocytes of five healthy subjects as well as purified normal B lymphocytes were used as controls. Leukemic lymphocytes of all donors expressed the same membrane phenotype, M receptor, and B7 and Ia antigens. The lymphocyte populations investigated were not completely free from myelomonocytic cells and contained small numbers of T lymphocytes. DNA synthesis was determined on days 3, 5, and 7 of culture by measuring the incorporation of tritiated thymidine. PWM-induced proliferation of leukemic B lymphocytes of nine patients was within normal limits, while the response of leukemic cells of six patients was very low. On the other hand, all CLL donors responded very well to PHA. Moreover, the response of leukemic B lymphocytes was significantly higher than the response of normal B cells. It was concluded that leukemic B lymphocytes of CLL patients are capable of proliferation after stimulation with PWM and PHA. The mechanisms underlying these responses to PWM and PHA are likely to be different.     

Detection of B-cell antigen on the blast cells in chronic myeloid leukemia]

The presence of the common antigen on B lymphocytes of healthy donors and myeloblasts of patients with chronic myeloid leukemia in blastic crisis was observed with antimyeloblastic serum in the indirect surface immunofluorescence test. The cytotoxic test showed this antigen in the blastic cells in 27 out of 57 patients with CML BC, in 3 of 11 patients with acute lymphoid leukemia, in 1 of 8 patients with chronic lymphoid leukemia and in 2 of 2 patients with undifferentiated leukemia. The antigen was not found in the peripheral blood cells of healthy donors.     

Heterogeneity of B-cell growth factor receptor reactivity in healthy donors and in patients with chronic lymphatic leukemia: relationship to B-cell-derived lymphokines

Twenty-five long-term B-cell lines were studied for B-BCGF activity. The cell lines were cultured in the presence or absence of the new tumor promoter teleocidin, and control and teleocidin-treated derived supernatants were cocultured with purified B cells obtained from healthy donors and patients with B chronic lymphatic leukemia (B-CLL), in the presence of anti-mu. In attempt to delineate the role of other B-cell lymphokines in promoting proliferation of activated B cells, the supernatants were also studied for interleukin 1 (IL-1), interleukin 2 (IL-2), and interferon gamma (IFN-gamma). The effect of B-cell-derived lymphokines on the proliferation of activated B cells obtained from the 14 donors was heterogeneous, and three types of response were observed: In four healthy donors there was induction of B-cell proliferation by B-cell lymphokines derived from both control cells and teleocidin-treated cells. In cells obtained from the other five healthy donors there was induction of B-cell proliferation by B-cell lymphokines derived from teleocidin-treated cells. In the five B-CLL patients, B-cell proliferative response to B-cell lymphokines derived from both control cells and teleocidin-activated cells was absent. Comparison of B-BCGF reactivity to T-BCGF reactivity demonstrated that B-CLL B lymphocytes did not respond to either B-BCGF or T-BCGF, whereas normal B cells responded to T-BCGF and may proliferate upon stimulation with B-cell-derived IL-2 and/or B-BCGF. These results suggest heterogeneity of B-BCGF receptor reactivity in B lymphocytes derived from healthy donors, and lack of both B-BCGF and T-BCGF receptor reactivities in B lymphocytes derived from B-CLL patients; B-cell-derived lymphokines influence normal B-cell response but not leukemic B cells; B-BCGF optimal effect is in large part due to other B-cell lymphokines, especially B-cell-derived IL-2; the possible existence of various B-BCGFs.     

T cells from indolent CLL patients prevent apoptosis of leukemic B cells in vitro and have altered gene expression profile

T cells may have a role in sustaining the leukemic clone in chronic lymphocytic leukemia (CLL). In this study, we have examined the ability of T cells from CLL patients to support the survival of the leukemic B cells in vitro. Additionally, we compared global gene expression of T cells from indolent CLL patients with healthy individuals and multiple myeloma (MM) patients. Apoptosis of purified leukemic B cells was inhibited in vitro when co-cultured with increasing numbers of autologous T cells (p < 0.01) but not autologous B and T cells of normal donors. The anti-apoptotic effect exceeded that of the anti-apoptotic cytokine IL-4 (p = 0.002) and was greater with CD8+ cells (p = 0.02) than with CD4+ cells (p = 0.05). The effect was depended mainly on cell–cell contact although a significant effect was also observed in transwell experiments (p = 0.05). About 356 genes involved in different cellular pathways were deregulated in T cells of CLL patients compared to healthy individuals and MM patients. The results of gene expression profiling were verified for 6 genes (CCL4, CCL5 (RANTES), XCL1, XCL2, KLF6, and TRAF1) using qRT–PCR and immunoblotting. Our results demonstrate that CLL-derived T cells can prevent apoptosis of leukemic B cells and have altered expression of genes that may facilitate the survival of the leukemic clone.     

HLA and leukemia

HLA-A, -B, -C characteristics were determined in 85 AML patients and in 47 ALL patients as well as in 95 pairs of parents of leukemic patients. The detected antigen frequencies of patients were compared with those of 2,947 donors from Leipzig. A significant increase of frequency was found for Cw4 and in the group of ALL patients (p = 0.05), an increase of frequency could be observed for B22 and in the group of PR/NR patients for pcor = 0.05. A correlation between A9 and longer survival time in leukemic patients could not be found. Parents of leukemic patients (but not the patients themselves) showed a limited genetic heterogeneity with respect to the HLA system.     

‘Conservative’ and ‘variable’ clusters of Alu-family DNA repeats in human chromosomes

The distribution of Alu-family DNA repeats (AFRs) in chromosomes of phytohaemagglutinin-stimulated peripheral blood lymphocytes of four normal donors and non-stimulated bone marrow cells of four patients with acute leukemia (ALL and ANLL) was studied by in situ hybridization using DNA of recombinant phage lambda containing multiple inserts of AFR as a probe. Over some chromosome bands (14cen, 16p13, 16cen) from normal donors and from leukemic patients clusters of silver grains were detected. Over other three bands (3q26, 8p11-p12 and 14q24) the clusters were found only in chromosomes from the four acute leukemia patients, and were absent from chromosomes of healthy donors. The results suggest non-random long-range distribution of AFRs in human chromosomes, and somatic variations in the distribution of the repeats.     

Role of the inhibitory KIR ligand HLA-Bw4 and HLA-C expression levels in the recognition of leukemic cells by Natural Killer cells

Transplantation of acute myeloid leukemia (AML) patients with grafts from related haploidentical donors has been shown to result in a potent graft-versus-leukemia effect. This effect is mediated by NK cells because of the lack of activation of inhibitory killer cell immunoglobulin-like receptors (KIRs) which recognize HLA-Bw4 and HLA-C alleles. However, conflicting results have been reported about the impact of KIR ligand mismatching on the outcome of unrelated HLA-mismatched hematopoietic stem cells transplants (HSCT) to leukemic patients. The interpretation of these conflicting results is hampered by the scant information about the level of expression of HLA class I alleles on leukemic cells, although this variable may affect the activation of inhibitory KIRs. Therefore in the present study, utilizing a large panel of human monoclonal antibodies we have measured the level of expression of HLA-A, -B and -C alleles on 20 B-chronic lymphoid leukemic (B-CLL) cell preparations, on 16 B-acute lymphoid leukemic (B-ALL) cell preparations and on 19 AML cell preparations. Comparison of the level of HLA class I antigen expression on leukemic cells and autologous normal T cells identified selective downregulation of HLA-A and HLA-B alleles on 15 and 14 of the 20 B-CLL, on 2 and 5 of the 16 B-ALL and on 7 and 11 of the 19 AML patients tested, respectively. Most interestingly HLA-C alleles were markedly downregulated on all three types of leukemic cells; the downregulation was most pronounced on AML cells. The potential functional relevance of these abnormalities is suggested by the dose-dependent enhancement of NK cell activation caused by coating the HLA-HLA-Bw4 epitope with monoclonal antibodies on leukemic cells which express NK cell activating ligands. Our results suggest that besides the HLA and KIR genotype, expression levels of KIR ligands on leukemic cells should be included among the criteria used to select the donor-recipient combinations for HSCT.     

Natural killer and lymphokine-activated killer cell functions in chronic myeloid leukemia

Summary The natural killer (NK) and lymphokine-activated killer (LAK) cell activities of peripheral blood lymphocytes from chronic myeloid leukemia (CML) patients in remission and from healthy donors have been studied. Regression analysis to compare both cytotoxic responses in individual donors and the frequency of LAK cell precursors was also carried out. About 42% of CML patients in remission showed low NK activity (less than the mean percentage NK activity of healthy donors — 2 SD) and were categorised as low NK responders. The stage of remission or the drugs used to bring about remission did not influence the NK status. The LAK activity of low NK as well as normal NK responder CML patients was significantly low against the NK-sensitive K562 cell line and the NK-resistant VIP (melanoma) and T-24 (bladder carcinoma) tumor targets, as assessed by linear regression analysis. Allogeneic leukemic cells were more resistant to killing, especially by patients' LAK cells. The frequency analysis of LAK cell precursors revealed a significant reduction in the LAK cell progenitor frequency in CML patients in remission.     

Identification of Novel HLA-A*24:02-Restricted Epitope Derived from a Homeobox Protein Expressed in Hematological Malignancies

The homeobox protein, PEPP2 (RHOXF2), has been suggested as a cancer/testis (CT) antigen based on its expression pattern. However, the peptide epitope of PEPP2 that is recognized by cytotoxic T cells (CTLs) is unknown. In this study, we revealed that PEPP2 gene was highly expressed in myeloid leukemia cells and some other hematological malignancies. This gene was also expressed in leukemic stem-like cells. We next identified the first reported epitope peptide (PEPP2^271-279). The CTLs induced by PEPP2^271-279 recognized PEPP2-positive target cells in an HLA-A*24:02-restricted manner. We also found that a demethylating agent, 5-aza-2’-deoxycytidine, could enhance PEPP2 expression in leukemia cells but not in blood mononuclear cells from healthy donors. The cytotoxic activity of anti-PEPP2 CTL against leukemic cells treated with 5-aza-2’-deoxycytidine was higher than that directed against untreated cells. These results suggest a clinical rationale that combined treatment with this novel antigen-specific immunotherapy together with demethylating agents might be effective in therapy-resistant myeloid leukemia patients.     

Suppression of the responsiveness of lymphocytes from cancer patients triggered by co-culture with autologous tumor-derived cells

The question as to whether or not cancer patients have "tumor antigen"-induced suppressor T cells is of considerable interest and importance. As an approach to that question, the effect of addition of autologous irradiated tumor-derived cells (TDC) on the mixed lymphocyte response (MLR) of patients' lymphocytes (Ly) and of healthy donor Ly was tested. The rationale for these experiments was based on the fact that circulating antigen-responsive blood lymphocytes can be reactivated in vitro by exposure to the appropriate antigen. Thus, if there are circulating tumor "antigen"-reactive suppressor Ly, exposure to TDC as a source of the antigen should reactivate those cells. Reactivation of suppressor cells might result in diminished responsiveness to other stimuli such as alloantigens in the mixed leukocyte culture. We found that the addition of TDC to Ly cultures produced four distinct patterns of reaction. In 26 of the 74 different patient-tumor assays, the addition of autologous TDC to the patient cultures inhibited MLR, but the addition of the same TDC to cultures of Ly from healthy donors had no effect or increased their responsiveness (Specific Suppression). In 21 cases, the addition of autologous TDC to the patient cultures suppressed the MLR and the addition of the same TDC to control cultures suppressed the response of some but not all the healthy donors (Selective Suppression). In four cases, the addition of TDC to the cultures suppressed the MLR of the patients and all of the control donors (Nonspecific Suppression). In 23 cases, the addition of autologous TDC resulted in no suppression of the patient MLR or of any of the simultaneously tested normal donors (No Suppression). When TDC of patients with noninvasive bladder cancer were added to their own Ly cultures, only four of 11 produced specific or selective suppression compared to 11 of 12 when TDC came from patients with superficially invasive cancer. These data provide indirect evidence to support the hypothesis that human tumors induce circulating suppressor cells that may be reactivated in vitro by co-culture with TDC.     

Augmentation of antileukemia lytic activity by OKT3 monoclonal antibody: synergism of OKT3 and interleukin-2

We have shown that short-term incubation (45 min) of peripheral blood lymphocytes of normal donors with OKT3 monoclonal antibody (MoAb), directed against T-cell-associated antigen CD3, resulted in an acquisition of lytic activity against fresh leukemic cells. Induction of such antileukemia activity was specific for OKT3, since Leu-1 MoAb (directed against another T cell surface molecule, CD5) did not induce a lytic effect. The OKT3-generated antileukemia effect was displayed against various types of leukemia including chronic myelogenous leukemia and acute myelogenous leukemia of various histological subtypes (M1, M2, M5). We furthermore demonstrated that OKT3 MoAb substantially enhanced leukemia killing by interleukin-2 (IL-2)-activated killer cells obtained from peripheral blood of patients with leukemia. Of most importance was the observation that the combined treatment of effector cells with IL-2 and OKT3 MoAb resulted in the highest levels of lysis of both autologous and allogeneic fresh leukemic cells that have been observed in leukemic patients to date. Of importance was to note that OKT3 treatment was effective in induction of cytotoxic activity also in patients whose effector cells were unresponsive to stimulation with IL-2 alone. All of these observations suggest that IL-2-activated and OKT3-MoAb-treated effector cells may represent the most aggressive population of antileukemia-directed killer cells and may play a significant role in the treatment of human leukemia.     

Identification of novel HLA-restricted preferentially expressed antigen in melanoma peptides to facilitate off-the-shelf tumor-associated antigen-specific T-cell therapies

Background aimsPreferentially expressed antigen in melanoma (PRAME) is a cancer/testis antigen that is overexpressed in many human malignancies and poorly expressed or absent in healthy tissues, making it a good target for anti-cancer immunotherapy. Development of an effective off-the-shelf adoptive T-cell therapy for patients with relapsed or refractory solid tumors and hematological malignancies expressing PRAME antigen requires the identification of major histocompatibility complex (MHC) class I and II PRAME antigens recognized by the tumor-associated antigen (TAA) T-cell product. The authors therefore set out to extend the repertoire of HLA-restricted PRAME peptide epitopes beyond the few already characterized.MethodsPeptide libraries of 125 overlapping 15-mer peptides spanning the entire PRAME protein sequence were used to identify HLA class I- and II-restricted epitopes. The authors also determined the HLA restriction of the identified epitopes.ResultsPRAME-specific T-cell products were successfully generated from peripheral blood mononuclear cells of 12 healthy donors. Ex vivo-expanded T cells were polyclonal, consisting of both CD4+ and CD8+ T cells, which elicited anti-tumor activity in vitro. Nine MHC class I-restricted PRAME epitopes were identified (seven novel and two previously described). The authors also characterized 16 individual 15-mer peptide sequences confirmed as CD4-restricted epitopes.ConclusionsTAA T cells derived from healthy donors recognize a broad range of CD4+ and CD8+ HLA-restricted PRAME epitopes, which could be used to select suitable donors for generating off-the-shelf TAA-specific T cells.     

Lymphocyte zinc metabolism in disease

Lymphocytes were obtained from two patients with paroxysmal nocturnal hemoglobinuria as well as from apparently healthy controls and from patients with acute lymphoblastic leukemia and chronic lymphocytic leukemia. Subsequently, several aspects of zinc metabolism were studied in vitro in short-term cultures of these lymphocytes in order to assess lymphocyte functional capacity. The results of mitogen stimulation and zinc uptake studies for lymphocytes from donors with paroxysmal nocturnal hemoglobinuria were similar to those obtained for leukemic lymphocytes. The results of studies to determine the inducibility of the low molecular weight zinc-binding protein, metallothionein, by zinc were complicated by the decrease in overall protein synthesis in lymphocytes from donors in the paroxysmal nocturnal hemoglobinuria. It is proposed that paroxysmal nocturnal hemoglobinuria is indeed a clonal disorder and the relationship between lymphocytes in this disorder and leukemic lymphocytes is discussed.     

Membranes of EBV-carrying virus nonproducer cells inhibit leukocyte migration of EBV-seropositive but not seronegative donors

We have previously shown that the leukocytes of healthy EBV-seropositive (but not seronegative) donors respond with migration inhibition (LMI) when confronted with extracts of EBV-carrying (but not EBV negative) cells. In the present study, we have examined whether this EBV-specific LMI response is capable of detecting a membrane antigen on the surface of EBV-carrying virus nonproducer cells. Crude membranes from EBV-genome carrying and EBV-negative cell lines were used as antigen. Contamination with the EBV-determined nuclear antigen (EBNA) was ruled out. Membranes from EBV-genome carrying nonproducer cells inhibited the migration of leukocytes from healthy seropositive donors, whereas membranes from EBV-negative lines had no such effect. Seronegative donors did not show any LMI. The clear difference between the EBV-negative Ramos line and its EBV-converted sublines was particularly conclusive in showing that the membrane component is determined or induced by the viral genome.     

Demonstration of antibodies binding to autologous and allogeneic leukemic cells in childhood ALL. Evidence for a common ALL antigen(s)

The humoral immune response to autologous leukemic cells was investigated in childhood ALL using a 125I protein A binding assay. In 5/7 patients antibodies were demonstrated at diagnosis and in 3/7 cases also after chemotherapy. Sera from 2/3 patients, which bound significantly to autologous leukemic cells, did not bind significantly to autologous remission cells. In allogeneic experiments sera bound significantly to ALL leukemic cells (6/7 positive combinations), but not to AML leukemic cells (8/8 negative combinations). We propose that ALL sera contain antibodies binding to autologous leukemic cells and that they are directed against a common ALL antigen(s).     

Detection of glucocorticoid receptors in leukemia cells by dexamethasone-induced cytolysis and [3H]-dexamethasone binding

The presence of glucocorticoid receptors on the leukemic cells of 33 patients affected with acute lymphatic leukemia (ALL) and 6 patients affected with acute myeloic leukemia (AML) was investigated by dexamethasone-induced cytolysis and [3H] dexamethasone binding. The tests undertaken proved that after 20 hours of incubation 9 of 26 non-T-non-B-ALL (c-ALL and unclassified ALL) and 2 of AML were lysed with dexamethasone; blood lymphocytes and bone marrow leukocytes of healthy donors, however, were not affected. Non-T-non-B-ALL and AML were able to bind essentially more [3H] dexamethasone than T-ALL. There existed no correlation between dexamethasone binding and dexamethasone-induced cytolysis.     

Measles-specific T cell clones derived from a twin with multiple sclerosis: genetic restriction studies

The association between multiple sclerosis (MS) and HLA-DR2 suggests that the disease may be associated with an aberrant immune response, likely directed against an antigen of either viral or host origin. We have used measles virus-specific T cell clones derived from a patient with MS to study genetic restriction patterns of antigen presentation by macrophage-enriched (E-) populations. Twenty-two clones proliferated in response to measles-infected Vero cells but not to mumps-infected or uninfected Veros. E- cells from both the autologous subject and her healthy, measles nonresponder identical twin were capable of presenting antigen to all clones. Studies with E- cells obtained from a panel of cell donors demonstrated clones which recognized antigen in association with D2/DR2, DR4, subgroups of DR4, and SB3. Three clones recognized antigen only in association with the autologous or twin's cells, but not with other sets of HLA-matched E-cells obtained from healthy donors or from other patients with MS. These studies indicate that the differing responses to measles virus demonstrated by these two identical twins are not explained by alterations in the interactions between antigen-presenting cells and T cells. Furthermore, at the clonal level, no preferential role is seen for HLA-DR2 as the restricting element for presentation of measles virus to these clones.     

Monocyte-derived dendritic cells exposed to Der p 1 allergen enhance the recruitment of Th2 cells: major involvement of the chemokines TARC/CCL17 and MDC/CCL22

Dendritic cells (DC) are potent antigen - presenting cells that can orientate the immune response towards a Th1 or a Th2 type. DC produce chemokines that are involved in the recruitment of either Th1 cells, such as IP10 (CXCL10), Th2 cells such as TARC (CCL17) and MDC (CCL22), or non-polarized T cells such as RANTES (CCL5) and MIP-lalpha (CCL3). We investigated whether monocyte-derived DC (MD-DC) generated from healthy donors or from patients sensitive to Dermatophagoides pteronyssinus (Dpt) and exposed to the cysteine-protease Der p 1(allergen of Dpt), could upregulate the expression of chemokines involved in type 1 or type 2 T cell recruitment. MD-DC were pulsed with either Der p 1 or with LPS as the control and the chemokines produced were evaluated using ELISA and chemotaxis assays. Der p 1-pulsed DC from allergic patients showed increased TARC (CCL17) and MDC (CCL22) production without modifying IP-10 (CXCL10) release. Der p 1-pulsed DC from healthy donors showed only increased IP-10 (CXCL10) secretion. RANTES (CCL5) and MIP-lalpha (CCL3) production were similarly increased when DC were from healthy or allergic donors. The selective Th2 clone recruitment activity of supernatants from Der p 1-pulsed DC of allergic patients was inhibited by anti-TARC (CCL17) and anti-MDC (CCL22) neutralizing Abs. By using anti-IP10 (CXCL10) blocking Abs, supernatants of Der p 1-pulsed DC from healthy donors were shown to be involved in the recruitment of Th1 cells. These results suggest that in allergic patients exposed to house dust mites, DC may favour the exacerbation of the Th2 response via the increase in type 2 chemokine production.