The purification of human basophils: their immunophenotype and cytochemistry

[The basophil: From control of immunity to control of leukemias]

The basophils, first described by Paul Ehlrich in 1879, are rare circulating cells, representing approximately 0.01 to 0.3% of the blood leukocytes. Until recently, these cells have been neglected because of their minority status among immune cells and because they show some similarities to mast cells residing in tissues. However, basophils and mast cells are now recognized as distinct cell lines and it appears that basophils have important and non-redundant functions, distinct from those of mast cells. On the one hand, basophils have beneficial contribution to protective immunity, in particular against parasitic infections. On the other hand, basophils are involved in the development of various benign and malignant pathologies, ranging from allergy to certain leukemias. Basophils interact with other immune cells or neoplastic cells through direct contacts or soluble mediators, such as cytokines and proteases, thus contributing to the regulation of the immune system but also to allergic responses, and probably to the process of neoplastic transformation. In this review, we will develop recent knowledge on the involvement of basophils in the modulation of innate and adaptive immunity. We will then describe the benign or malignant circumstances in which an elevation of circulating basophils can be observed. Finally, we will discuss the role played by these cells in the pathophysiology of certain leukemias, particularly during chronic myeloid leukemia.

Purification of Basophils from Peripheral Human Blood

The purification of basophils from peripheral blood has represented a formidable challenge for researchers since they were discovered by Paul Ehrlich in 1879. From the first published attempts in the late 1960s, it took half a century to develop robust protocols able to give sufficient numbers of pure, functionally unimpaired basophils. The existing protocols for basophil purification exploit those properties of basophils which distinguish them from other cell types such as their localization in blood, density, and the presence or absence of surface markers. Purification techniques have been used in various combinations and variations to achieve a common goal in mind: to obtain a pure population of human basophils in sufficient numbers for downstream studies. The arduous way leading up to the modern protocols is summarized in this historical retrospective. A fast protocol for purification of basophils to near homogeneity is also described.

Proposed diagnostic criteria and classification of basophilic leukemias and related disorders

Basophils form a distinct cell lineage within the hematopoietic cell family. In various myeloid neoplasms, including chronic myeloid leukemia, basophilia is frequently seen. Acute and chronic basophilic leukemias, albeit rare, have also been described. However, no generally accepted criteria and classification of basophilic leukemias have been presented to date. To address this unmet need, a series of Working Conferences and other meetings were organized between March 2015 and March 2016. The current article provides a summary of consensus statements from these meetings, together with proposed criteria to delineate acute basophilic leukemia (ABL) from chronic basophilic leukemia (CBL) and primary forms of the disease where no preceding myeloid malignancy is detected, from the more common 'secondary' variants. Moreover, the term hyperbasophilia (HB) is proposed for cases with a persistent peripheral basophil count ⩾1000 per μl of blood. This condition, HB, is highly indicative of the presence of an underlying myeloid neoplasm. Therefore, HB is an important checkpoint in the diagnostic algorithm and requires a detailed hematologic investigation. In these patients, an underlying myeloid malignancy is often found and is then labeled with the appendix -baso, whereas primary cases of ABL or CBL are very rare. The criteria and classification proposed in this article should facilitate the diagnosis and management of patients with unexplained basophilia and basophil neoplasms in routine practice, and in clinical studies.

Enumeration and immunohistochemical characterisation of bone marrow basophils in myeloproliferative disorders using the basophil specific monoclonal antibody 2D7

BACKGROUND

Basophils are highly specialised granulocytes that express a unique profile of antigens and increase in myeloproliferative disorders (MPD). In chronic myeloid leukaemia (CML), basophilia is a diagnostic and prognostic determinant. So far, however, no reliable approach for routine detection and enumeration of bone marrow basophils has become available.

OBJECTIVE

To detect and enumerate basophils in bone marrow sections in patients with CML and other MPD.

METHODS

The anti-basophil antibody 2D7 was applied to paraffin embedded bone marrow sections from normal/reactive subjects (n = 31), patients with CML (chronic phase, n = 37; accelerated phase, n = 9), and other MPD (chronic idiopathic myelofibrosis (CIMF), n = 20; polycythaemia vera (PV), n = 20; essential thrombocythaemia (ET), n = 20; indolent systemic mastocytosis (ISM), n = 7).

RESULTS

As assessed by serial section staining, 2D7(+) cells were found to co-express myeloperoxidase, histidine decarboxylase, CD9, and CD43, but did not express B cell or T cell restricted antigens. 2D7(+) bone marrow cells were found to increase in CML compared with normal/reactive bone marrow and other MPD (median numbers of 2D7(+) cells/mm(2): CML, 33; normal/reactive bone marrow, 6; CIMF, 10; PV, 6; ET, 5; ISM, 3; p<0.05). The highest basophil counts were recorded in accelerated phase CML (115/mm(2)).

CONCLUSIONS

A novel immunohistochemical procedure has been established for basophil detection in normal bone marrow and MPD. This approach should help in the quantification of bone marrow basophils at diagnosis and during anti-leukaemic treatment.

Identification of CD13, CD107a, and CD164 as novel basophil-activation markers and dissection of two response patterns in time kinetics of IgE-dependent upregulation

Using two-colour flow cytometry >200 antibodies submitted to the 8th International Workshop of Human Leukocyte Differentiation Antigens (HLDA8) have been analyzed for their reactivity with resting and activated CD203c+ basophils. Four antibodies either non-reactive or weakly reactive with resting basophils exhibited an increased reactivity with basophils activated by anti-IgE-mediated cross-linking of the high affinity IgE receptor (FceRI). These include antibodies against CD164 (WS-80160, clone N6B6 and WS-80162, clone 67D2), as well as two reagents with previously unknown specificities that were identified as CD13 (WS-80274, clone A8) and CD107a (WS-80280, clone E63-880). The activation patterns followed either the "CD203c-like" or "CD63-like" activation profile. The CD203c profile is characterized by a rapid and significant upregulation (of CD13, CD164, and CD203c), reaching maximum levels after 5-15 min of stimulation. The Phosphoinositide-3-kinase (PI3K)-specific inhibitor Wortmannin inhibited the upregulation of these markers whereas 12-O-tetradecanoyl-phorbol-13-acetate (TPA) induced a rapid and FceRI-independent upregulation within 1-2 min. In the CD63 profile, maximum upregulation (of CD63 and CD107a) was detected only after 20-40 min, and upregulation by TPA reached maximum levels after 60 min. In summary, our data identify CD13, CD107a, and CD164 as novel basophil-activation antigens. Based on time kinetics of upregulation, we hypothesize that molecules of the "CD203c group" and the "CD63 group" are linked to two different mechanisms of basophil activation.

Immunoglobulin E (IgE) containing complexes induce IL-4 production in human basophils: effect on Th1-Th2 balance in malaria

Human basophils are potent producers of IL-4 following cross-linking of the high affinity receptor for IgE (Fc epsilon R1). Elevated levels of both total- and malaria-specific IgE have been demonstrated in sera from people living in malaria-endemic regions. Whether or not these IgE antibodies are pathogenic is unclear. Serum containing high IgE levels obtained from malaria individuals was used to establish whether IgE-immune complexes could induce IL-4 production in human basophils. The basophils, obtained from healthy donors, were primed with 10 ng/ml of IL-3 before being transferred to wells containing goat anti-human IgE or human antimalarial IgE-immune complexes. IL-4 was induced upon stimulation of human basophils by plate bound IgE-containing immune complexes. Basophils treated similarly but with goat anti-IgG/human antimalarial- IgG-immune complexes did not secrete IL-4. Similarly mononuclear cells depleted of basophils in parallel culture did not secrete IL-4. Thus, human basophils may contribute to the polarization of T-helper type 2 in the (Th2) responses in malaria hosts via IgE-induced IL-4 production.

Mass, charge, and subcellular localization of a unique secretory product identified by the basophil-specific antibody BB1

BACKGROUND

BB1 is a basophil-specific mAb (Lab Invest 1999;79:27-38). The identity of the corresponding antigen has not been determined, but it gives a granular appearance on staining and is secreted on activation of basophils.

OBJECTIVE

We sought to further characterize the basophilspecific antigen identified by BB1.

METHODS

Intracellular localization was determined by flow cytometry and by immunogold labeling and electron microscopy. Physical chemical properties were investigated by gel filtration chromatography and preparative isoelectric focusing.

RESULTS

In flow cytometry, permeabilization of cells increased immunofluorescence 100-fold, confirming the predominantly intracellular localization of the antigen. It was further localized to the secretory granules by immunoelectron microscopy. Double labeling with a CD63-specific antibody demonstrated selective binding of BB1 to the granule matrix. Gel filtration chromatography indicated that the antigen is secreted as a complex of approximately 5 x 10(6) d, which was well resolved from the 210-kd supramolecular complex containing tryptase. The antigen was degraded by pronase. Isoelectric focusing indicated a highly basic protein with an isoelectric point of 9.6.

CONCLUSION

With its granule localization, release on cell activation, and unique properties, the antigen identified by BB1 could be a novel mediator of allergic disease. We propose the name basogranulin for this novel basophil-specific protein.

Simplified purification of human basophils

Studies of human basophils have been limited by the low number present in peripheral blood and the difficulties of purification to homogeneity with reasonable yield and functional status. Reproducible purification of human basophils to 96.5+/-0.5% with a yield of 40.8+/-5.3% was obtained by negative selection using immunomagnetic beads following initial separation by density gradient centrifugation. Isolated cells demonstrated complete viability by vital dye exclusion and spontaneous histamine release following incubation of <5%. Stimulation with anti-IgE or calcium ionophore A23187 caused histamine release and leukotriene C(4) production. Basophils demonstrated dose-dependent chemotaxis to monocyte chemotactic protein-3. This simplified methodology results in fully functional basophils in very high purity and good yield.

Modulation of histidine decarboxylase activity and cytokine synthesis in human leukemic cell lines: relationship with basophilic and/or megakaryocytic differentiation

In the present study, we show that UT7D1 cells, derived from the pluripotent cell line UT7, express high levels of histidine decarboxylase (HDC) mRNA spontaneously. These cells conserve the ability to differentiate into megakaryocytes upon stimulation with PMA, while greatly increasing their HDC activity. We provide evidence that enhanced HDC activity reflects the basophil rather than the megakaryocytic differentiation potential of UT7DI cells. Indeed, in addition to HDC mRNA, they express spontaneously several other mRNA coding for molecules present in basophils (FcepsilonRI, CCR3, IL-4Ralpha, IL-5Ralpha). Furthermore, the basophil antigen Bsp-1 is displayed on the surface of some UT7D1 cells in response to PMA concomitantly with increased histamine synthesis and mRNA expression of typical basophil-derived cytokines (IL-6, IL-4, and IL-13). Nevertheless, PMA cannot sustain the differentiation of this lineage, because mRNAs for basophil markers gradually diminish during long-term culture, whereas molecules associated with the megakaryocytic lineage remain prominent. In support of the notion that HDC activity is not related with megakaryopoiesis, we show that PMA-induced CD41 expression and PDGF transcription occurs in the K562 cells, though neither HDC mRNA nor any known basophil marker are expressed in these conditions. In contrast, all these markers are expressed in the basophilic leukemia cell line KU812F. Interestingly, the megakaryocytic cell line HEL produces also substantial amounts of histamine and expresses FcepsilonRI, thus revealing its basophil differentiation potential. HEL as well as KU812F need not be stimulated with PMA to react with Bsp-1 mAb, suggesting that they are more engaged into the basophil differentiation scheme than UT7D1. Other leukemic cell lines unrelated to the megakaryocyte or basophil lineage, like HL60 and U937 do neither synthesize histamine nor express basophil markers before or after PMA stimulation. To our knowledge, this is the first evidence for a factor-dependent cell line with megakaryocyte/basophil bipotentiality with which early stages of basophil commitment can be analyzed.

Purification of morphologically and functionally intact human basophils to near homogeneity

Certain studies on basophils require highly purified functionally intact cell preparations. Here, a three-step procedure is described that meets these requirements. The procedure consists of a Ficoll density gradient step, counterflow elutriation and negative selection by magnetic cell sorting (MACS). The mean purity of basophils obtained from 30 donors was 97.6+/-3.96% with a viability of 99.6+/-0.83%. The recovery rate was 49.7+/-15.6%. The cells had a normal morphological appearance as assessed by May-Grünwald-stained cytospins and were functionally intact as shown by their unaltered capacity to release histamine and interleukin 4 (IL-4) following immunological activation. This procedure is a clear improvement over currently available techniques and should facilitate future investigations on basophils.

Diagnosis of acute basophilic leukemia

De novo acute basophilic leukemia (ABL) is a rare form of acute leukemia. Most frequently, the blast cells are morphologically undifferentiated, and the recognition of the presence of coarse basophilic granules may be the first step in diagnosis of this rare disorder. These granules are metachromatic and MPO negative. Immunophenotyping shows myeloid markers and some more specifically associated antigens such as CD9 or CD25 which are strongly expressed. Lymphoid, erythroid or megakaryocytic markers are not significantly expressed. In the absence of basophilic granules, some cases are classified as AML M0 if they express myeloid markers, or undifferentiated leukemia if no markers are present. If specific immature basophilic or theta granules are present, only an electron microscopic study will enable the diagnosis of a basophilic lineage assignment. Some cases may be misdiagnosed if all these steps are not followed. After all these investigations, two types of ABL may be defined: 1-A pure ABL, monophenotypic with basophilic lineage involvement alone, which should be classified as AML M8 . Genetic studies in these cases are very important for understanding the leukemic process and in a few cases, we can suspect c-MYB oncogene involvement but further investigations are still necessary. 2- More frequently, acute leukemia can be a mixture of blasts from different lineages with an important but variable participation of mature or immature basophilic cells. These cases must be classified as AML/Baso or multiphenotypic acute leukemias and often present Phl -chromosomal abnormality.

Identification of Basophilic Cells that Express Mast Cell Granule Proteases in the Peripheral Blood of Asthma, Allergy, and Drug-Reactive Patients

Metachromatic cells in the peripheral blood of patients with asthma, allergy, or an allergic drug reaction were evaluated for their nuclear morphology, surface expression of the mast cell (MC) marker c-kit, surface expression of the basophil marker Bsp-1, and granule expression of MC proteases. Consistent with previous findings by others, Bsp-1+/metachromatic cells represented &lt;1% of the cells in the peripheral blood of normal individuals. These cells generally contained segmented nuclei. Very little, if any, tryptase (Try), chymase (Chy), or carboxypeptidase A (CPA) was found in their granules, and very little, if any, c-kit was observed on their surfaces. The number of metachromatic cells increased in the peripheral blood of the three groups of patients. Like the basophils in normal individuals, most of these metachromatic cells contained segmented nuclei and expressed Bsp-1. However, in contrast to the basophils in normal individuals, many of the metachromatic cells in the three patient groups expressed c-kit, Try, Chy, and/or CPA. That the metachromatic cells in the blood of our patients have some features of MCs and some features of basophils suggests that human basophils and MCs are derived from a common progenitor. As assessed by the chloroacetate esterase cytochemical assay, the immunoreactive Chy in the peripheral blood of these patients is enzymatically active. Because MC proteases regulate numerous immunologic and other biologic systems, the expression of Try, Chy, and/or CPA in a peripheral blood-localized cell in an individual having asthma, allergy, or an allergic drug reaction has important clinical implications.

Identification of CD68+lin− Peripheral Blood Cells with Dendritic Precursor Characteristics

Expression of CD68 (macrosialin) in the absence of surface and lysosomal lineage marker molecules is a characteristic feature of T zone-associated plasmacytoid monocytes, which were recently shown to represent precursors of dendritic cells (DC). We demonstrate here a minor population of strongly CD68-positive (CD68bright) blood cells that lack all analyzed myeloid surface (CD14−, CD33−, CD13−, CD11b−, CD11c−) and lysosomal (myeloperoxidase, MPO− and lysozyme, LZ−) marker molecules (0.4 ± 2% of the total mononuclear cells). These CD68bright, lineage marker-negative (lin−) cells can be induced to proliferate in the presence of IL-3. They do not acquire myeloid features even upon stimulation with granulocyte-macrophage CSF plus IL-1, IL-3, and IL-6. Instead, these cells develop typical DC characteristics upon culture. Furthermore, these CD68brightlin− DC precursors acquire mature DC characteristics (CD86+, CD83+, CD54bright) upon stimulation with CD40 ligand plus IL-3. A second subset of DC precursor-like blood cells was found to weakly express CD68 (0.3 ± 0.2% of the total mononuclear cells) and to coexpress several myeloid lineage associated molecules (LZ+, CD11c+, CD33+, CD13+). Cells of this second subset resemble both previously described myeloid-related peripheral blood DC and germinal center DC. Analysis of peripheral blood leukocytes for CD68 thus revealed the existence of two cell subsets that phenotypically resemble lymphoid tissue-associated DC. The unique phenotype CD68brightlin− is highly reminiscent of T zone-associated plasmacytoid monocytes. CD68brightlin− blood leukocytes also functionally resemble plasmacytoid monocytes. The lack of all analyzed myeloid features by CD68brightlin− blood leukocytes suggests that these cells arise from a novel nonmyeloid human DC differentiation pathway.

Cell biology of the basophil

The cell biology of basophils, based on published studies spanning 1990-1997, is reviewed. These rarest cells of granulocyte lineages are now available in sufficient numbers for such studies to be done, based on new methods for isolating and purifying the cells from peripheral blood and organ sources and for their derivation in growth factor-containing cultures from their precursors de novo. These studies are dependent on electron microscopy for the accurate identification of basophils, studies which have recently established the presence of basophils in two new species--mice and monkeys. Secretory, endocytotic and storage properties of basophils constitute their mechanistic role(s) in human disease; their role(s) in health is, however, obscure. Development of immunoaffinity and enzyme-affinity ultrastructural labeling techniques to image the Charcot-Leyden crystal protein and histamine in human basophils, coupled with ultrastructural analysis of kinetic samples of cells obtained after stimulation with diverse secretogogues, has provided insight into the role of vesicles in secretory transport mechanisms in human basophils as well as the definition of key ultrastructural phenotypes of secreting basophils.

Purification of human basophils and mast cells by multistep separation technique and mAb to CDw17 and CD117/c-kit

Basophils and mast cells represent distinct cell lineages within the hemopoietic system. Based on the unique cell surface antigen profile of both cells, we have established methods which allow the reproducible purification to homogeneity (> 99%) of normal human basophil granulocytes from the peripheral blood and of mast cells from human dispersed tissues. Basophils (n = 9) were purified by current counterflow elutriation followed by depletion of monocytes with CD14 mAb conjugated to magnetic beads, and subsequent cell sorting for CD217+ cells. Basophil purity was 99.5 +/- 0.4% (range 98.7-99.9%). Mast cells were obtained from lung (n = 6), uterus (n = 1), mastocytosis bone marrow (n = 2), and human foreskin (n = 2). Mast cells were purified by collagenase digestion followed by current counterflow elutriation and sorting with CD117/c-kit mAb. Mast cell purity was 99.4 +/- 0.7% (range: 97.5-99.9%). Purified cells were more than 90% viable and were able to release histamine on induction with IgE plus anti-IgE. Furthermore, the PCR technique could be applied on pure cells and confirmed expression of high affinity IgE receptor (Fc epsilon R1) alpha chain mRNA. Thus, by combining isolation techniques including elutriation, magnetic cell depletion and cell sorting with mAb, functionally intact normal human basophils and mast cells can be enriched to homogeneity.

Flow cytometric monitoring of allergen induced basophil activation

Human basophils express many clustered differentiation antigens (CD), including CD45; however, none are specific for these cells. In a previous study, we described a two-color immunofluorescence procedure, employing antibodies to CD45 and IgE for the cytometric evaluation of basophils. In the present work, we show that when sensitized basophils are stimulated by allergenic preparations, they demonstrate an upregulation of CD45 as well as a decrease in anti-IgE binding. Since CD45 antigen modulation was observed with all aeroallergens tested and the decrease in IgE expression varied with allergenic preparations, the measurement of CD45 upregulation was used to evaluate basophil activation. Using this approach, reproducible results were observed when atopic patients were tested at different time intervals. In addition, we show that the upregulation of CD45 on allergen stimulated basophils is a very rapid phenomenon that is observed after a few minutes and that this rapid flow cytometric method can also be used for investigations on nonallergenic mediators of basophil stimulation such as calcium ionophores.

Purification of human basophils by density and size alone

Basophils typically account for approximately 1% of the white cells in peripheral blood. We have developed a unique method for purifying basophils from whole blood of normal subjects to at least 95% purity. Basophils are separated from other cell types by density-dependent sedimentation in Percoll and cell sorting, based solely on their size and granularity. The mean overall yield ranged from 5% to 28%. The procedure is typically completed within 4 h. The highly purified basophils obtained are functionally competent and morphologically intact. They release histamine in response to Fc epsilon RI-mediated stimulation, express Fc epsilon RI and BSP-1 ligand as analyzed by flow cytometry, and exhibit the known characteristic ultrastructural features of basophils by electron microscopy. This procedure avoids positive-selection antibodies that might perturb receptors on basophils or negative-selection antibodies that might activate other cell types, and can be used to obtain basophils for studies in vitro.

Purification of human blood basophils and leukotriene C4 generation following calcium ionophore stimulation

A simple method for purification of basophils from a relatively small volume of blood has been developed, which enables us to collect basophils with a purity of over 80%. Basophils were partially purified from 10-20 ml of citrated whole blood using the discontinuous Percoll density gradient centrifugation technique and then contaminant cells were removed using monoclonal antibodies against CD2, CD19, CD14 and CD16. At the end of the procedure, basophils were > 80% pure with lymphocytes accounting for most of the contaminating cells. When stimulated with anti-IgE or fMLP, histamine release from purified basophils was similar to that from mixed leukocytes. When highly purified basophils were challenged with calcium ionophore A23187, generation of leukotriene C4 (LTC4) was not significantly different between asthmatic patients and normal subjects (45.6 +/- 22.6 vs 52.7 +/- 25.6 ng/10(6) cells). Basophils were capable of generating LTC4 in approximately the same quantities as eosinophils (46.5 +/- 11.7 ng/10(6) cells, n = 3). Furthermore, it has been shown that incubation of basophils and eosinophils with calcium ionophore generates only small quantities of thromboxane B2 (TXB2).

Purification of human blood basophils by negative selection using immunomagnetic beads

A simple and rapid method for isolating highly purified and functionally intact basophils from normal human blood is described. Blood from healthy volunteers was centrifuged through a two layer Percoll density gradient. The majority of the basophils were recovered between Percoll layers with densities of 1.070 and 1.080, constituting 45.6% of total leukocytes. Lymphocytes, monocytes and neutrophils were extracted from this fraction using a panel of mabs in a direct or indirect selection procedure using immunomagnetic beads (Dynabeads) coated with sheep anti-mouse IgG. These negative immunoselection procedures produced a high yield of basophils with a mean purity of 97.8% (range 93.0-99.5%) and 97.0% (range 96.2-99.0%) using the direct and indirect method, respectively. The cells isolated by this method are viable, release histamine to various stimuli in a normal manner, and appear morphologically normal in transmission electron microscopy.

Flow cytometric evaluation of human basophils

The expression of CD45 and IgE cell surface antigens on human leucocytes was studied by flow cytometry. More than 80% of sorted cells that expressed low CD45 (CD45dim) and high IgE (IgEbright) antigen site density were identified as basophils. Immunomagnetic depletion of the CD45dim-IgEbright cell subset by a biotin-coupled anti-IgE antibody and streptavidin-coated magnetic beads was greater than 90%, and more than 80% of cells binding significant numbers of beads exhibited the morphological characteristics of basophils. Interestingly, when the cell staining was performed in the presence of calcium and magnesium, we observed a significant increase of CD45 and an equivalent decrease of IgE cell surface expression, as well as an IgE concentration dependent diminution of the number of CD45dim-IgEbright cells.

Abnormal granulopoiesis of leukemic cells with basophil/mast cell features. Cytochemical and ultrastructural observations

We have carried out cytochemical and ultrastructural examination of human leukemic cells showing basophil/mast cell features derived from patients with acute myelogenous leukemia or basophilic crisis in chronic myelogenous leukemia. Leukemic cells in each case initially showed metachromasia with toluidine blue and various degrees of positivity for astra blue. Other cytochemical results showed considerable variety among cases. The number of granules increased in short-term culture in every case. Ultrastructurally, small membrane-bound granules with or without myelinoid bodies or glycogen particles were present in immature blasts, followed by production of other granule types. In some cases, leukemic cells before and after liquid culture contained the typical basophil granules with or without myelinoid bodies, but the matrix was more loose than normal. Granules showing whorl or scroll matrix profiles, which were typical for mast cells, were present in two cases. In one case, immature leukemic cells contained theta granules, and some mature forms after short-term culture contained typical basophil/mast cell granules as well as theta granules. Leukemic cells occasionally contained multivesicular granules predominantly. These results indicate that leukemic cells with basophil/mast cell features show a heterogeneous configuration and contain abnormal granules differing from normal ones. This abnormal granulopoiesis may be attributable to the results of leukemic events and may be a hallmark for recognition of leukemic basophils/mast cells.

Characterization of leukaemic basophil progenitors from chronic myelogenous leukaemia

We describe the unique characteristics of leukaemic basophils from a patient with chronic myelogenous leukaemia (CML). The leukaemic cells were immature basophil-like blasts and expressed CD4, CD7 and HLA-DR in addition to CD13 and CD33. Both immunoglobulin and T cell receptor genes were retained in germline configurations. Interleukin-1 (IL-1) or granulocyte-macrophage colony-stimulating factor (GM-CSF) as well as IL-3 or IL-4 enhanced the proliferation and differentiation of leukaemic cells and only basophils were generated from in vitro culture. These results suggest that basophil progenitors expressing CD4, CD7 and HLA-DR may be involved in the development of basophilic crisis of CML and that both IL-1 and GM-CSF may act on basophil progenitors as well as IL-3 or IL-4.

Heterogeneity of Leukemic Cells with Basophilic Features: Cytochemical, Ultrastructural and Immunophonotypic Analysis of 8 Cases

We have studied leukemic cells, derived from acute nonlymphocytic leukemia with basophilic features and basophilic crisis of chronic myelogenous leukemia (CML), by cytochemical and ultrastructural examination and analysis of surface markers. Cytochemical results varied from case to case, while the ultrastructural appearances of the granules were different from normal granules. The granules had more delicate granular matrices with or without myelinoid figures, whorled or scroll matrix, multivesicular bodies structures, theta granules, and crystalloid structures. Leukemic cells in all cases had myeloid surface markers with some degree of variability. In addition, they were occasionally positive for lymphoid markers, but not for CD10 and IgE receptors. The present results show that leukemic cells with basophilic features are heterogeneous in their morphology, cytochemistry and surface markers.

An unusual form of chronic myeloproliferative disorder. Aleukemic basophilic leukemia

A 52-year-old Japanese man manifested various clinical signs and symptoms such as vomiting, high fever, dyspnea, cough, sweating, palpitation, eosinophilic leukocytosis and hepatosplenomegaly. These histamine-related clinical manifestations showed a dramatic response to steroid therapy. After 10 months of hospitalization, he suddenly succumbed to candidal septicemia at the end of the third cycle of steroid therapy. Autopsy revealed neoplastic proliferation of immature basophils in various internal organs without involvement of the skin. The neoplastic cells, positive immunohistochemically for leukocyte common antigen, possessed lobulated nuclei and weakly metachromatic cytoplasmic granules, predominantly of the basophil type, which exhibited weak naphthol ASD-chloroacetate esterase activity. Mast cell-type granules were also observed ultrastructurally. The neoplastic infiltration was associated with fibrosis in the liver, spleen and bone marrow and with extramedullary hematopoiesis in the liver, spleen, lymph nodes and perihypophyseal tissue. The bone marrow showed uneven and multifocal involvement. Despite the lack of leukemic manifestations and the results of chromosomal analysis, the most suitable diagnosis was aleukemic basophilic leukemia within the category of chronic myeloproliferative disorder. Kinship of this neoplasia to systemic mastocytosis is discussed.

Flow cytometric methods for the analysis of human basophil surface antigens and viability

Fluorescence and flow microfluorometric methods have been established for the detection and evaluation of IgE-bearing human leukocytes in various cell preparations including those where basophils are present at low percentages. Quantitative techniques for the determination of basophil purity, viability, and cell surface antigens including IgE are described. Use of these methods will facilitate the identification and phenotypic analysis of human IgE-bearing cells in a wide variety of biological fluids.