A multicentre verification study of the QuantiFERON®-TB Gold Plus assay.

OBJECTIVES: The aim of this verification study was to compare the QuantiFERON®-TB Gold Plus (QFT-Plus) to the QuantiFERON®-TB Gold In Tube (QFT-GIT). The new QFT-Plus test contains an extra antigen tube which, according to the manufacturer additionally elicits a CD8+ T-cell response above the CD4+ T-cell response. We assessed the value of this tube in detecting recent latent tuberculosis infections. METHODS: Between May 2015 and December 2016, 1031 subjects underwent QFT-Plus and QFT-GIT test. Overall agreement between both tests and performance for different test indications and/or immune states was assessed. A difference of >0.6 IU/mL interferon-γ release between the two antigen tubes of the QFT-Plus assay was considered a true difference and used as estimation for CD8+ T-cell response. RESULTS: Analysis of the QuantiFERON tests resulted in an overall agreement between assays of 95%. Subjects considered to be recently exposed to tuberculosis had significantly more often a true difference in interferon-γ release compared to all other subjects (p = 0.029). CONCLUSION: Results of QFT-Plus are highly comparable to QFT-GIT. Although there is an indication that a true difference in interferon-γ release between the antigen tubes is associated with recent latent tuberculosis infection, the QFT-Plus could not be used to exclude recent exposure.

Patients with gout have short telomeres compared with healthy participants: association of telomere length with flare frequency and cardiovascular disease in gout.

AIM AND BACKGROUND: Chronic inflammation associates with increased senescence, which is a strong predictor for cardiovascular disease. We hypothesised that inflammation accelerates senescence and thereby enhances the risk of cardiovascular disease in gout. METHODS: We assessed replicative senescence by quantifying telomere length (TL) in a discovery cohort of 145 Dutch patients with gout and 273 healthy individuals and validated our results in 474 patients with gout and 293 healthy participants from New Zealand. Subsequently, we investigated the effect of cardiovascular disease on TL of all participants. Also, we measured TL of CD4+ and CD8+ T lymphocytes, B lymphocytes, monocytes, natural killer cells and plasmacytoid dendritic cells. Additionally, we assessed the potential temporal difference in TL and telomerase activity. RESULTS: TL in PBMCs of healthy donors decreased over time, reflecting normal ageing. Patients with gout demonstrated shorter telomeres (p=0.001, R2=0.01873). In fact, the extent of telomere erosion in patients with gout was higher at any age compared with healthy counterparts at any age (p<0.0001, R2=0.02847). Patients with gout with cardiovascular disease had the shortest telomeres and TL was an independent risk factor for cardiovascular disease in patients with gout (p=0.001). TL was inversely associated with the number of gouty flares (p=0.005). CONCLUSIONS: Patients with gout have shorter telomeres than healthy participants, reflecting increased cellular senescence. Telomere shortening was associated with the number of flares and with cardiovascular disease in people with gout.

IgG4-related disease: a disease we probably often overlook.

IgG4-related disease (IgG4-RD) is an increasingly recognised entity characterised by tumefied lesions that can affect multiple organs. Awareness of IgG4-RD is important, as it has been shown to mimic other diseases and may result in irreversible organ damage if not treated. If suspected, immunostaining for IgG4-positive plasma cells is essential for diagnosis and revision of old biopsies may be necessary.

High endothelial venules associated with T cell subsets in the inflamed gut of newly diagnosed inflammatory bowel disease patients.

Naive and central memory T lymphocytes (TN and TCM ) can infiltrate the inflamed gut mucosa in inflammatory bowel disease (IBD) patients. Homing of these subsets to the gut might be explained by ectopic formation of tertiary lymphoid organs (TLOs), containing high endothelial venules (HEVs). We aimed to evaluate the presence of HEVs and TLOs in inflamed intestinal mucosa of newly diagnosed, untreated IBD patients in relation to the presence of TN and TCM lymphocytes. IBD patients (n = 39) and healthy controls (n = 8) were included prospectively. Biopsy samples of inflamed and normal intestine, respectively, were analysed by immunohistochemistry for lymphocytes (CD3/CD20), blood vessels (CD31) and peripheral lymph node addressin (PNAd) expression (MECA-79). TN and TCM lymphocyte subsets were identified by flow cytometric immunophenotyping. A higher number of HEVs was found in the inflamed colon of patients with ulcerative colitis [median 3·05 HEV/mm2 ; interquartile range (IQR) = 0-6·39] and ileum of Crohn's disease patients (1·40; 0-4·34) compared to healthy controls (both 0; P = 0·033). A high density of colonic HEVs (HEVhigh ) was associated with increased infiltration of TN and TCM in the inflamed gut (median 87%; IQR = 82-93% of T cell population), compared to HEVlow patients (58%; 38-81%; P = 0·003). The number of colonic follicles was higher in HEVhigh patients (median 0·54/mm2 ; IQR 0·28-0·84) compared to HEVlow patients (0·25/mm2 ; 0·08-0·45; P = 0·031) and controls (0·31/mm2 ; 0·23-0·45; P = 0·043). Increased homing of TN and TCM lymphocytes to inflamed gut tissue in IBD patients might be facilitated by ectopic formation of extrafollicular HEVs and TLOs in a subgroup of patients.

Immunophenotypic differentiation patterns of normal hematopoiesis in human bone marrow: reference patterns for age-related changes and disease-induced shifts.

BACKGROUND: The abundance of monoclonal antibodies (mAb) and the routine use of quadruple stainings in flow cytometry allow stepwise analysis of bone marrow (BM) samples that are suspected for abnormal hematopoiesis. A screening phase that precedes lineage-specific classification phases should be sufficient to assess whether the BM has a normal or abnormal composition, as well as to identify the abnormal differentiation lineage. METHODS: For a quick and easy flow cytometric screening of BM samples, we selected six quadruple immunostainings that cover multiple differentiation stages of the B-cell, monocytic, granulocytic, and erythroid lineages: TdT/CD20/CD19/CD10 and CD45/CD34/CD19/CD22 for B cells, CD34/CD117/CD45/CD13.33 for precursor granulocytic and precursor monocytic cells (myelo/monoblasts), CD14/CD33/CD45/CD34 for monocytic cells, CD16/CD13/CD45/CD11b for granulocytic cells, and CD71/CD235a/CD45/CD117 for erythroid cells. RESULTS: The six quadruple immunostainings reveal specific staining patterns in normal BM, which allow the recognition of various subpopulations of the respective lineages. These staining patterns can be used as a frame of reference for recognition of normal and abnormal BM development. Examples of normal (age-related) variations in these otherwise stable staining patterns are presented together with several abnormal differentiation patterns. CONCLUSIONS: Although alternative immunostainings can be used (e.g., including NK- and T-cell markers), we feel that the selected six stainings represent a comprehensive and easy screening phase for quick identification of shifts in the composition of the studied differentiation lineages, reflecting age-related changes or disease-induced BM abnormalities.

Three-color flowcytometric analysis of mature and immature hematological malignancies. A guideline of the Dutch Foundation for Immunophenotyping of Hematological Malignancies (SIHON).

Multiparameter flowcytometry offers an insight into differentiation pathways, maturation stages and abnormal features of cell (sub)populations thus helping to establish and classify hematological malignancies. The Dutch Foundation for Immunophenotyping of Hematological Malignancies (SIHON) has formulated a guideline for a rapid screening followed by confirmation and classification in a standardized way. For this aim seven carefully composed monoclonal antibody combinations are elucidated for screening the test sample in a first phase. In this phase a relative frequency distribution of the cells will be established and a decision will be made about abnormal cells present, as well as their mature or immature state and the cell lineage they belong to. In a second phase, panels with cell lineage dependent monoclonal antibody combinations may be used to confirm and classify the abnormal cell population indicated in phase 1, as well as to establish the presence or absence of an abberant immunophenotype.

Therapeutic immune reconstitution in HIV-1-infected children is independent of their age and pretreatment immune status.

OBJECTIVE: To evaluate long-term immune reconstitution of children treated with highly active antiretroviral therapy (HAART). METHODS: The long-term immunological response to HAART was studied in 71 HIV-1-infected children (aged 1 month to 18 years) in two prospective, open, uncontrolled national multicentre studies. Blood samples were taken before and after HAART was initiated, with a follow-up of 96 weeks, and peripheral CD4 and CD8 T cells plus naive and memory subsets were identified in whole blood samples. Relative cell counts were calculated in relation to the median of the age-specific reference. RESULTS: The absolute CD4 cell count and percentage and the CD4 cell count as a percentage of normal increased significantly (P < 0.001) to medians of 939 x 106 cells/l (range, 10-3520), 32% (range, 1-50) and 84% (range, 1-161), respectively, after 48 weeks. This increase was predominantly owing to naive CD4 T cells. There was a correlation between the increase of absolute naive CD4 T cell counts and age. However, when CD4 T cell restoration was studied as percentage of normal values, the inverse correlation between the increase of naive CD4 T cell count and age was not observed. In addition, no difference in immunological reconstitution was observed at any time point between virological responders and non-responders. CONCLUSIONS: Normalization of the CD4 cell counts in children treated with HAART is independent of age, indicating that children of all age groups can meet their CD4 T cell production demands. In general, it appears that children restore their CD4 T cell counts better and more rapidly than adults, even in a late stage of HIV-1 infection.

BIOMED-I concerted action report: flow cytometric immunophenotyping of precursor B-ALL with standardized triple-stainings. BIOMED-1 Concerted Action Investigation of Minimal Residual Disease in Acute Leukemia: International Standardization and Clinical Evaluation.

The flow cytometric detection of minimal residual disease (MRD) in precursor-B-acute lymphoblastic leukemias (precursor-B-ALL) mainly relies on the identification of minor leukemic cell populations that can be discriminated from their normal counterparts on the basis of phenotypic aberrancies observed at diagnosis. This technique is not very complex, but discordancies are frequently observed between laboratories, due to the lack of standardized methodological procedures and technical conditions. To develop standardized flow cytometric techniques for MRD detection, a European BIOMED-1 Concerted Action was initiated with the participation of laboratories from six different countries. The goal of this concerted action was to define aberrant phenotypic profiles in a series of 264 consecutive de novo precursor-B-ALL cases, systematically studied with one to five triple-labelings (TdT/CD10/CD19, CD10/CD20/CD19, CD34/CD38/CD19, CD34/CD22/CD19 and CD19/CD34/CD45) using common flow cytometric protocols in all participating laboratories. The use of four or five triple-stainings allowed the identification of aberrant phenotypes in virtually all cases tested (127 out of 130, 98%). These phenotypic aberrancies could be identified in at least two and often three triple-labelings per case. When the analysis was based on two or three triple-stainings, lower incidences of aberrancies were identified (75% and 81% of cases, respectively) that could be detected in one and sometimes two triple-stainings per case. The most informative triple staining was the TdT/CD10/CD19 combination, which enabled the identification of aberrancies in 78% of cases. The frequencies of phenotypic aberrations detected with the other four triple-stainings were 64% for CD10/CD20/CD19, 56% for CD34/CD38/CD19, 46% for CD34/CD22/CD19, and 22% for CD19/CD34/CD45. In addition, cross-lineage antigen expression was detected in 45% of cases, mainly coexpression of the myeloid antigens CD13 and/or CD33 (40%). Parallel flow cytometric studies in different laboratories finally resulted in highly concordant results (>90%) for all five antibody combinations, indicating the high reproducibility of our approach. In conclusion, the technique presented here with triple-labelings forms an excellent basis for standardized flow cytometric MRD studies in multicenter international treatment protocols for precursor-B-ALL patients.

Molecular and flow cytometric analysis of the Vbeta repertoire for clonality assessment in mature TCRalphabeta T-cell proliferations.

Clonality assessment through Southern blot (SB) analysis of TCRB genes or polymerase chain reaction (PCR) analysis of TCRG genes is important for diagnosing suspect mature T-cell proliferations. Clonality assessment through reverse transcription (RT)-PCR analysis of Vbeta-Cbeta transcripts and flow cytometry with a Vbeta antibody panel covering more than 65% of Vbeta domains was validated using 28 SB-defined clonal T-cell receptor (TCR)alphabeta(+) T-ALL samples and T-cell lines. Next, the diagnostic applicability of the V(beta) RT-PCR and flow cytometric clonality assays was studied in 47 mature T-cell proliferations. Clonal Vbeta-Cbeta RT-PCR products were detected in all 47 samples, whereas single Vbeta domain usage was found in 31 (66%) of 47 patients. The suspect leukemic cell populations in the other 16 patients showed a complete lack of Vbeta monoclonal antibody reactivity that was confirmed by molecular data showing the usage of Vbeta gene segments not covered by the applied Vbeta monoclonal antibodies. Nevertheless, this could be considered indirect evidence for the "clonal" character of these cells. Remarkably, RT-PCR revealed an oligoclonal pattern in addition to dominant Vbeta-Cbeta products and single Vbeta domain expression in many T-LGL proliferations, providing further evidence for the hypothesis raised earlier that T-LGL derive from polyclonal and oligoclonal proliferations of antigen-activated cytotoxic T cells. It is concluded that molecular Vbeta analysis serves to assess clonality in suspect T-cell proliferations. However, the faster and cheaper Vbeta antibody studies can be used as a powerful screening method for the detection of single Vbeta domain expression, followed by molecular studies in patients with more than 20% single Vbeta domain expression or large suspect T-cell populations (more than 50%-60%) without Vbeta reactivity.

Flow cytometric analysis of the Vbeta repertoire in healthy controls.

BACKGROUND: Analysis of the T-cell receptor (TCR)-Vbeta repertoire has been used for studying selective T-cell responses in autoimmune disease, alloreactivity in transplantation, and protective immunity against microbial and tumor antigens. For the interpretation of these studies, we need information about the Vbeta repertoire usage in healthy individuals. METHODS: We analyzed blood T-lymphocyte (sub)populations of 36 healthy controls (age range: from neonates to 86 years) with a carefully selected most complete panel of 22 Vbeta monoclonal antibodies, which together recognized 70-75% of all blood TCRalphabeta(+) T lymphocytes. Subsequently, we developed a six-tube test kit with selected Vbeta antibody combinations for easy and rapid detection of single ("clonal") Vbeta domain usage in large T-cell expansions. RESULTS: The mean values of the Vbeta repertoire usage were stable during aging in blood TCRalphabeta(+) T lymphocytes as well as in the CD4(+) and CD8(+) T-cell subsets, although the standard deviations increased in the elderly. The increased standard deviations were caused by the occurrence of oligoclonal T-cell expansions in the elderly, mainly consisting of CD8(+) T lymphocytes. The 15 detected T-cell expansions did not reach 40% of total TCRalphabeta(+) T lymphocytes and represented less than 0.4 x 10(9) cells per liter in our study. Vbeta usage of the CD4(+) and CD8(+) subsets was comparable for most tested Vbeta domains, but significant differences (P < 0.01) between the two subsets were found for Vbeta2, Vbeta5.1, Vbeta6.7, Vbeta9.1, and Vbeta22 (higher in CD4(+)), as well as for Vbeta1, Vbeta7.1, Vbeta14, and Vbeta23 (higher in CD8(+)). Finally, single Vbeta domain expression in large T-cell expansions can indeed be detected by the six-tube test kit. CONCLUSIONS: The results of our study can now be used as reference values in studies on distortions of the Vbeta repertoire in disease states. The six-tube test kit can be used for detection of single Vbeta domain expression in large T-cell expansions (>2.0 x 10(9)/l), which are clinically suspicious of T-cell leukemia.

BIOMED-1 concerted action report: flow cytometric characterization of CD7+ cell subsets in normal bone marrow as a basis for the diagnosis and follow-up of T cell acute lymphoblastic leukemia (T-ALL).

The European BIOMED-1 Concerted Action was initiated in 1994 to improve and standardize the flow cytometric detection of minimal residual disease (MRD) in acute leukemia (AL). Three different protocols were defined to identify the normal subsets of B, T and myeloid cells in bone marrow (BM), and were applied to the different types of AL in order to study aberrant immunophenotypes. Using sensitive acquisition methods ('live gate') T cell subsets in normal BM could be identified with five triple-stains: CD7/CD5/CD3, CD7/CD4/CD8, CD7/CD2/CD3, CD7/CD38/CD34 and TdT/CD7/surface or cytoplasmic (cy)CD3 (antibodies conjugated with FITC/PE/PECy5 or PerCP, respectively). The identification of T cell subsets in BM allowed definition of 'empty spaces' (ie areas of flow cytometric plots where normally no cells are found). All studied T-ALL cases (n = 65) were located in 'empty spaces' and could be discriminated from normal T cells. The most informative triple staining was TdT/CD7/cyCD3, which was aberrant in 91% of T-ALL cases. In most cases, two or more aberrant patterns were found. Apparently the immunophenotypes of T-ALL differ significantly from normal BM T cells. This is mostly caused by their thymocytic origin, but also the neoplastic transformation might have affected antigen expression patterns. Application of the five proposed marker combinations in T-ALL contributes to standardized detection of MRD, since cells persistent or reappearing in the 'empty spaces' can be easily identified in follow-up BM samples during and after treatment.

Regeneration pattern of precursor-B-cells in bone marrow of acute lymphoblastic leukemia patients depends on the type of preceding chemotherapy.

Immunofluorescence stainings for the CD10 antigen and terminal deoxynucleotidyl transferase (TdT) can be used for the detection of leukemic blasts in CD10+ precursor-B-acute lymphoblastic leukemia (precursor-B-ALL) patients, but can also provide insight into the regeneration of normal precursor-B-cells in bone marrow (BM). Over a period of 15 years, we studied the regeneration of CD10+, TdT+, and CD10+/TdT+ cells in BM of children with (CD10+) precursor-B-ALL during and after treatment according to three different treatment protocols of the Dutch Childhood Leukemia Study Group (DCLSG) which differed both in medication and time schedule. This study included a total of 634 BM samples from 46 patients who remained in continuous complete remission (CCR) after treatment according to DCLSG protocols VI (1984-1988; n = 8), VII (1988-1991; n = 10) and VIII (1991-1997; n = 28). After the cytomorphologically defined state of complete remission with CD10+ and CD10+/TdT+ frequencies generally below 1% of total BM cells, a 10-fold increase in precursor-B-cells was observed in protocol VII and protocol VIII, but not in protocol VI. At first sight this precursor-B-cell regeneration during treatment resembled the massive regeneration of the precursor-B-cell compartment after maintenance treatment, and appeared to be related to the post-induction or post-central nervous system (CNS) therapy stops in protocols VII and VIII. However, careful evaluation of the distribution between the 'more mature' (CD10+/TdT-) and the 'immature' (CD10+/TdT+) precursor-B-cells revealed major differences between the post-induction/post-re-induction precursor-B-cell regeneration (low 'mature/immature' ratio: generally <1.0), the post-CNS treatment regeneration (moderate 'mature/immature' ratio: 1.2-2.8), and the post-maintenance regeneration (high 'mature/ immature' ratio: 5.7-7.6). We conclude that a therapy stop of approximately 2 weeks is already sufficient to induce significant precursor-B-cell regeneration even from aplastic BM after induction treatment. Moreover, differences in precursor-B-cell regeneration patterns are related to the intensity of the preceding treatment block, with lower 'mature/immature' ratios after the highly intensive treatment blocks. This information is essential for a correct interpretation of flow cytometric immunophenotyping results of BM samples during follow-up of leukemia patients. Particularly in precursor-B-ALL patients, regeneration of normal precursor-B-cells should not be mistaken for a relapse.

Flow cytometric analysis of normal B cell differentiation: a frame of reference for the detection of minimal residual disease in precursor-B-ALL.

During the last two decades, major progress has been made in the technology of flow cytometry and in the availability of a large series of monoclonal antibodies against surface membrane and intracellular antigens. Flow cytometric immunophenotyping has become a diagnostic tool for the analysis of normal and malignant leukocytes and it has proven to be a reliable approach for the investigation of minimal residual disease (MRD) in leukemia patients during and after treatment. In order to standardize the flow cytometric detection of MRD in acute leukemia, a BIOMED-1 Concerted Action was initiated with the participation of six laboratories in five different European countries. This European co-operative study included the immunophenotypic characterization and enumeration of different precursor and mature B cell subpopulations in normal bone marrow (BM). The phenotypic profiles in normal B cell differentiation may form a frame of reference for the identification of aberrant phenotypes of precursor-B cell acute lymphoblastic leukemias (precursor-B-ALL) and may therefore be helpful in MRD detection. Thirty-eight normal BM samples were analyzed with five different pre-selected monoclonal antibody combinations: CD10/CD20/CD19, CD34/CD38/CD19, CD34/CD22/CD19, CD19/CD34/CD45 and TdT/CD10/CD19. Two CD19- immature subpopulations which coexpressed B cell-associated antigens were identified: CD34+/CD22+/CD19- and TdT+/CD10+/CD19-, which represented 0.11 +/- 0.09% and 0.04 +/- 0.05% of the total BM nucleated cells, respectively. These immunophenotypes may correspond to the earliest stages of B cell differentiation. In addition to these minor subpopulations, three major CD19+ B cell subpopulations were identified, representing three consecutive maturation stages; CD19dim/CD34+/TdT+/CD10bright/CD22dim/CD45dim /CD38bright/CD20- (subpopulation 1), CD19+/CD34-/TdT-/CD10+/CD22dim/CD45+/CD38bright/ CD20dim (subpopulation 2) and CD19+/CD34-/TdT-/CD10-/CD22bright/CD45bright/ CD38dim/CD20bright (subpopulation 3). The relative sizes of subpopulations 1 and 2 were found to be age related: at the age of 15 years, the phenotypic precursor-B cell profile in BM changed from the childhood 'immature' profile (large subpopulations 1 and 2/small subpopulation 3) to the adult 'mature' profile (small subpopulation 1 and 2/large subpopulation 3). When the immunophenotypically defined precursor-B cell subpopulations from normal BM samples are projected in fluorescence dot-plots, templates for the normal B cell differentiation pathways can be defined and so-called 'empty spaces' where no cell populations are located become evident. This allows discrimination between normal and malignant precursor-B cells and can therefore be used for MRD detection.

Functional expression of minor histocompatibility antigens on human peripheral blood dendritic cells and epidermal Langerhans cells.

Adequate presentation and cell surface expression of foreign minor histocompatibility antigens (mHag) to allogeneic T cells can lead to graft versus-host disease (GvHD) after HLA matched bone marrow transplantation (BMT). Cells of the dendritic cell (DC) lineage, including epidermal Langerhans cells (LC), are the most potent inducers of primary alloreactive T cell responses in vivo and in vitro. To explore the possible role of peripheral blood DC and of skin derived LC in the induction of alloimmune responses against mHag, we analysed the functional expression of mHag on these professional antigen-presenting cells (APC). To this end, cytotoxic T cell (CTL) clones specific for mHag H-Y and HA-1 to HA-4 were used to demonstrate the presence of these antigens on highly purified DC and LC. Our results demonstrate that, like other cells of the hematopoietic lineage, DC and LC express all the mHag tested for. The functional expression of mHag on these potent APC suggests their involvement in the induction of mHag specific GvH directed T cell responses after allogeneic BMT.

Analysis of dendritic-cell-induced primary T-cell responses between HLA genotypically identical individuals.

DCs are known for their superior antigen-processing and antigen-presenting capacities. They are capable of processing intact protein: either endocytosed exogenous proteins or newly synthesized endogenous viral and bacterial proteins. They are potent inducers of primary T-cell immune responses such as in allogeneic MLRs. It is also known that DCs can provide a strong stimulus for autologous T-cell proliferation. So far no information exists on the capacity of DCs to induce primary mH antigen-specific T-cell responses. Therefore, we investigated whether human DCs, isolated from peripheral blood, were able to generate specific T-cell responses between MLR-negative HLA genotypically identical individuals in vitro. To this end, unfractionated cells, monocytes, and B cells were assayed in parallel with DCs to compare their capacity to activate unprimed T cells in a primary MLR. DCs indeed induced significant proliferation between HLA genotypically identical siblings, whereas the other APCs were unable to evoke any T-cell response at all. As expected, besides these allogeneic T-cell responses, autologous T-cell responses were initiated by the DCs as well. Nonetheless, despite further detailed analyses of the responding T cells, neither proliferative nor cytotoxic mH antigen-specific reactivities could yet be detected using the stimulation protocols described herein.

Epstein-Barr virus infection abrogates the stimulatory capacity of B cells to a major histocompatibility complex class-II-restricted proliferative T-cell clone.

After BMT, donor T cells are activated which can display GvHD as well as GvL activities. In order to study this GvL-specific T-cell response in vitro, proliferative T-cell clones from post-BMT PBMCs were generated by stimulation with a patient's leukemic cells. One CD4+ T-cell clone (designated M-33) displayed strong proliferative activity against the patient's leukemic cells but not against the patient's EBV-LCLs. The induction of proliferation, however, appeared not to be leukemia specific. Detailed analysis of the reactivity patterns revealed that T-cell clone M-33 recognizes an as yet unknown nonpolymorphic determinant in the context of self HLA-DRw52, presented by all but one type of APC. T-cell clone M-33 proliferated upon stimulation by PB-MCs, freshly isolated B cells, monocytes, dendritic cells, leukemic B cells, and nonleukemic B-cell blasts; solely in vitro EBV-transformed B cells and in vivo EBV-infected B cells failed to induce proliferation of T-cell clone M-33. Neither surface expression of MHC or accessory molecules on the EBV cells nor suppression caused by the EBV-infected cells could explain their failure to stimulate T-cell clone M-33. We therefore hypothesize that the absence of the stimulatory capacity once the B cells are virally infected could be the result of competition for MHC class II binding of the Epstein-Barr viral peptides, thus affecting the postulated DRw52-restricted peptide for recognition by T-cell clone M-33.

In vitro separation of host specific graft-versus-host and graft-versus-leukemia cytotoxic T cell activities.

The association of graft-versus-host disease (GVHD) with lower relapse rates following allogeneic bone marrow transplantation (BMT) in humans led us to analyse post HLA-identical BMT derived anti-host cytotoxic T cells (CTL) for their putative anti-leukemic activity. To establish whether graft-versus-host (GVH) and graft-versus-leukemia (GVL) activities are separate, CTL lines were generated at different time points post-BMT from three patients suffering from acute GVHD. These CTL lines, which exhibited lysis of host normal lymphocytes and neoplastic cells, were analysed at the clonal level. Three functionally different types of clones were characterized: clones directed at host specific minor Histocompatibility (mH) antigens which are shared by patient's peripheral blood lymphocytes (PBL) and leukemic cells; clones recognizing only host PBL but not host leukemic cells; and putative GVL clones directed at patient's neoplastic cells only. These data could explain the long controversies on dissection of GVH and GVL activities. Our results demonstrate that GVH and GVL activities can be dissected, while non-separable effector cells which exhibit both activities do exist as well.