Analysis of human leukemia/lymphoma cell lines with monoclonal antibodies BA-1, BA-2 and BA-3

N-(4-hydroxyphenyl)retinamide increases ceramide and is cytotoxic to acute lymphoblastic leukemia cell lines, but not to non-malignant lymphocytes

The retinoid, N-(4-hydroxyphenyl)retinamide (4-HPR), mediates p53-independent cytotoxicity and can increase reactive oxygen species and ceramide in solid tumor cell lines. We determined changes in ceramide and cytotoxicity upon treatment with 4-HPR (3-12 microM) in six human acute lymphoblastic leukemia (ALL) cell lines: T cell (MOLT-3, MOLT-4, CEM), pre-B-cell (NALM-6, SMS-SB), and null cell (NALL-1). Exposure to 4-HPR (12 microM) for 96 h caused 4.7 (MOLT-3), 3.5 (MOLT-4), 3.9 (CEM), 2.9 (NALM-6), 4.7 (SMS-SB), AND 4.5 (NALL-1) logs of cell kill. The average 4-HPR concentration that killed 99% of cells (LC(99)) for all six lines was 4.8 microM (range: 1.5-8.9 microM). Treatment with 4-HPR (9 microM) for 24 h resulted in an 8.9 +/- 1.0-fold (range: 4.9-15.7-fold) increase of ceramide. Ceramide increase was time- and dose-dependent and abrogated by inhibitors of de novo ceramide synthesis. Concurrent inhibition of ceramide glycosylation/acylation by d,l-threo-(1-phenyl-2-hexadecanoylamino-3-morpholino-1-propanol) (PPMP) further increased ceramide levels, and synergistically increased 4-HPR cytotoxicity in four of six ALL cell lines. 4-HPR was minimally cytotoxic to peripheral blood mononuclear cells and a lymphoblastoid cell line, and increased ceramide <2-fold. Thus, 4-HPR was cytotoxic and increased ceramide in ALL cell lines, but not in non-malignant lymphoid cell types.

Shedding of CD9 antigen in acute lymphoblastic leukemia

A leukemia-associated CD9 glycoprotein antigen released into the extracellular milieu from acute lymphoblastic leukemia cells has been detected using a unique lectin-monoclonal antibody immunoassay. It has been demonstrated that the release of CD9 antigen is an active process and is associated with active cell growth. In addition, the difference of carbohydrate moiety, and hence glycosylation, in the CD9 antigen derived from lymphoblasts and neuroblasts was verified using lectin affinity chromatography. The lectin affinity of the carbohydrate moiety of lymphoblast CD9 antigen would indicate the presence of N-linked oligosaccharide chains having groups of N-acetyl glucosamine residues, a mannose core and a terminal D-galactose. The soluble CD9 antigen is specifically detected in plasma from ALL patients at the time of diagnosis, in cerebrospinal fluid from patients with central nervous system involvement, and spent medium from CD9-positive leukemic blasts obtained at the time of diagnosis. Interestingly when bone marrow cells taken from patients in complete remission were studied, a distinct amount of CD9 antigen was released into spent medium in some of the cases. All of these patients have subsequently developed hematological relapse. The present data suggest that shedding of CD9 antigen by leukemic cells may enable the clinical monitoring of residual leukemic cell burden.

Radiation sensitivity of human B-lineage lymphoid precursor cells

We studied the radiation sensitivity of eight immunophenotypically distinct B-lineage lymphoid precursor cell (LPC) lines of acute lymphoblastic leukemia (ALL) or fetal liver origin corresponding to discrete developmental stages of human B-cell ontogeny. The radiation sensitivity of B-lineage LPC showed a temporal association with the distinct stages of development. FL112 and FL114 fetal liver pro-B cells (Stage 0 B-lineage LPC) with germline immunoglobulin heavy chain (IgH) genes but rearranged T-cell receptor gamma (T gamma) genes (DO of FL112 = 80.3 cGy, DO of FL114 = 50.2 cGy), REH ALL pre-pre-B cells (Stage I B-lineage LPC) with rearranged IgH and T gamma genes (DO = 66.1 cGy), and NALM-6 ALL pre-pre-B/pre-B cells (Stage II B-lineage LPC) (DO = 50.5 cGy) corresponding to the earliest three stages of human B-lymphocyte development were the most radiation sensitive B-lineage LPC populations. By comparison, KM-3 ALL pre-B (Stage III B-lineage LPC) (DO = 194.7 cGy), HPB-NULL ALL pre-B (Stage IV B-lineage LPC) (DO = 134.6 cGy), and sIgM+ RAJI/NAMALWA early B (Stage Va/b B-lineage LPC) cell lines (DO of RAJI = 144.0 cGy, DO of NAMALWA = 165.5 cGy) corresponding to the later stages of human B-lymphocyte development were much more radiation resistant. These results indicate that the radiation sensitivity of B-lineage LPC decreases during maturation within the B-lineage lymphoid precursor pathway. By comparison, the S-phase index (% of S-phase cells as determined by DNA flow cytometry) or proliferation index (% S + G2M), cellular protein content, intracellular glutathione (GSH) level, glutathione-S-transferase (GST) activity, intracellular pH, or free cytoplasmic calcium concentration did not correlate with the radiation sensitivity of the B-lineage LPC.

Transitions in CD45 isoform expression indicate continuous differentiation of a monoclonal CD5+ CD11b+ B lineage in Waldenstrom's macroglobulinemia

Waldenstrom's macroglobulinemia (WM) has been hypothesized to be a pleomorphic B-cell malignancy with persistent maturation towards plasma cells in all lymphoid tissue. This proposal is based on detection of a heterogeneous density of monoclonal Ig on peripheral blood B-cells in patients with WM. We now present data derived from 2- and 3-color immunofluorescence and flow cytometric analysis that strongly supports this hypothesis. Abnormally high numbers of B lineage cells, defined by expression of CD19, CD20, and CD24, were found among peripheral blood mononuclear cells (PBMC). These B-cells are monoclonal as defined by light chain expression and by the existence of rearranged Ig genes (Southern blot analysis), although they exhibit heterogeneity in the density of surface light chain. Unlike normal PBMC B-cells, the monoclonal B-cells bear CD5 and CD10 (CALLA), express adhesion and adhesion-related molecules (CD11b, CD9), and appear to be actively differentiating during the course of the disease, based on the pattern of CD45 isoform expression. At any given point in time, the population of monoclonal B-cells is heterogeneous in differentiation stage based on transitions in the expression of CD45 isoforms from expression of CD45RA, the high molecular mass isoforms of CD45, to the low molecular mass isoform CD45R0 which appears only on very late stage B-cells and early plasma cells. For one patient, analysis of CD45 isoform expression over 2 years showed that the monoclonal B-cell population as a whole progressed towards terminal differentiation as defined by loss of CD45RA and acquisition of CD45R0. This indicates a continuously differentiating lineage of an unusual B-cell phenotype, and/or malignant transformation of a distinct lineage of B-cells in WM.

Establishment from an adult leukemic patient of two novel precursor B cell lines with different growth modality

Two novel cell lines, PC-53 and PC-53A were established from an adult ALL patient, at third relapse and in the terminal accelerated phase respectively. Both lines displayed the phenotype of B-cell precursors (CD19+, CD38+, CD20-, cytoplasmic-mu-, immunoglobulin gene rearrangement), identical to the freshly isolated blast cells. Chromosomal analysis showed a prominent 45-XX karyotype, including three marker chromosomes. No chromosome 8 abnormalities were detectable, consistently with a non-rearranged c-myc locus. Both cell lines were EBV-negative. Growth stimulation by autologous supernatant was observed for PC-53 cells during the first 4 months in culture, whereas it was much less evident for PC-53A cells. Thus, PC-53 and PC-53A cells represent a useful tool to investigate the mechanisms involved in the clonal expansion of B-cell precursors.

Abnormalities in lymphocyte profile and specificity repertoire of patients with Waldenstrom's macroglobulinemia, multiple myeloma, and IgM monoclonal gammopathy of undetermined significance

The characteristics of T and B lymphocyte profile and B lymphocyte specificity repertoire were compared in patients with Waldenstrom's macroglobulinemia (WM), IgM monoclonal gammopathy of undetermined significance (IgM MGUS), multiple myeloma (MM), and age-matched normal subjects. Patients with MM had both significantly reduced frequency and number of sIg+ (surface Ig) B cells, whereas patients with WM and IgM MGUS had a reduced frequency but normal numbers of sIg+ B cells in circulation as detected in a capping assay. WM was distinguished by the large numbers of cells in the peripheral blood lymphocyte (PBL) pool that expressed CD9 (BA-2) and CD24 (BA-1) and were monoclonal, based on light chain analysis using flow cytometry. The profile of T lineage cells showed that the ratio of CD4:CD8 was significantly reduced in both MM and WM due to a reduction in the CD4 set. The CD4+ cells were qualitatively abnormal as well, with an enriched proportion of the 4B4+ (CDw29) subset and decreased proportion of the Lp220+ (CD45R) subset. This appeared to be an effect of the disease process on the relatively immature Lp220+ set. From clonal analysis, those patients with WM or IgM MGUS (unlike MM patients) did not exhibit enhanced reactivity with auto-Ig determinants, and most WM patients (7/8) and half of the IgM MGUS patients (3/6) did not have enriched proportions of B cells reactive to tetanus toxoid (TT). The TT-specific B cells in both WM and IgM MGUS, in contrast to MM, appeared fully functional in secretion of anti-TT IgM in vivo. We speculate that the more severe immunodeficiency in MM may be controlled or exacerbated by the presence of an anti-Ig network. The absence of this network in WM allows a relatively more effective immune response, but the immunodeficiency that is observed in these patients involves some abnormality in normal lymphocyte differentiation (is also present in MM).

The functional glycoprotein CD9 is variably acylated: localization of the variably acylated region to a membrane-associated peptide containing the binding site for the agonistic monoclonal antibody 50H.19

Recent studies have shown that [3H]palmitic acid strongly labels both glycosylated forms (gp22 and gp24) of the signal-initiating cell surface glycoprotein CD9. We performed a two-dimensional limited proteolysis analysis with Staphylococcus aureus V8 proteinase in order to localize the palmitylation sites to final peptides on both glycosylated forms of CD9. Analysis of [3H]leucine- and [3H]amino acid mixture-labeled gp22 delineated 4 final peptides of 11, 8, 7 and 4 kDa. gp24 produced a similar pattern with the exception that the 11 kDa peptide was replaced by an N-glycosylated 13 kDa peptide. Since all four final peptides (total molecular mass of 30/32 kDa) could not be accommodated by a parent molecule of 22/24 kDa, it is likely that one of the final peptide coexists in two differently modified states. Palmitic acid labeled the 11 kDa/13 kDa final peptides, and the 7 kDa final peptide, with equal intensity, but was not incorporated into the 4 kDa final peptide, demonstrating that fatty acid is ligated in two distinct regions of the molecule. The 8 kDa final peptide was strongly labeled by [3H]palmitic acid, but only weakly by [3H]leucine. We present evidence that this peptide is derived by further acylation of the region defined by the 7 kDa peptide, and that this occurs in only 15% of the molecules. Palmitic acid is turned over faster at these additional sites, indicating that they may be more accessible to membrane transacylases. Proteolysis of CD9 on the intact cell with papain enabled the highly acylated region to be localized to a membrane-associated fragment which contains the binding site for the agonistic monoclonal antibody 50H.19. The co-localization of a functional domain with a region of variable acylation suggests that acylation events may play a role in the transduction of the signal initiated by interaction of the antibody with CD9.

Novel type of proliferating lymphoplasmacytoid cell with a characteristic spotted immunofluorescence pattern

We examined bone marrow from myeloma patients for the presence of cells with the characteristics of the clonogenic cell in the myeloma stem cell assay. We identified a novel type of cell that contained cytoplasmic immunoglobulin of the relevant idiotype located in a cytoplasmic spot. This "spotted" Ig could be located in the rough endoplasmic reticulum. Spotted cells are highly proliferative, as evidenced by the nuclear staining with the antibody Ki67, and were found in the bone marrow from most of the myeloma patients studied. This type of cell was also present in patients with immunocytomas, in some cases of benign monoclonal gammopathy, and in patients in the state of polyclonal hypergammaglobulinemia. IgG subclass distribution of so-called spotted cells and plasma cells, found in a patient with pseudo biclonal gammopathy, indicates that spotted cells are intermediate between B cells and plasma cells. Spotted cells express the B cell-associated antigens HB4 and HB6 but do not express other B cluster of differentiation antigens or plasmacytoid antigens tested.

Expression of B-cell-specific markers in different Burkitt lymphoma subgroups

Forty-three Burkitt lymphoma (BL) lines were examined for the expression of 5 monoclonal antibody (MAb)-identified B-cell-specific markers and immunoglobulin production. All (13) EBV-negative BL lines were CALLA+ LB-1-, whereas 30 EBV-carrying lines showed a more heterogeneous pattern. In the EBV-negative lines, the follicle mantle zone markers BA-1 and 35.1C5 were expressed concordantly, at a different level in each line. This coordination was disrupted in EBV-carrying lines. In the EBV-negative lines, there was also an inverted correlation between the expression of 35.1C5 and the germinal center marker BLA, suggesting that some etiologically important event, perhaps the translocation, had fixed the cells at different stages of their transition from one zone to the other. This inverted relationship was also disrupted in the EBV-carrying lines, suggesting that EBV can interfere with the maturation program of the BL cell. This conclusion was also supported by a comparison between 5 EBV-negative BL lines and their EBV-converted sublines. All converted lines have undergone marker changes, but the degree and nature of these changes was different for each EBV-BL line. Both the coordinated expression of BA-1 and 35.1C5 and the inverted relationship between CALLA and LB-1 were disrupted in several other convertants. We have reexamined our previous finding (Ehlin-Henriksson and Klein, 1984) that the majority of the variant translocation-carrying BL lines were CALLA- LB-1+, in contrast to the majority of the typical translocation carriers that were mostly CALLA+ LB-1-. All II EBV-negative lines were CALLA+ LB-1-, irrespective of the type of translocation. Among the EBV-carrying lines, 4 of 17 typical (8;14) translocation carriers were CALLA- LB-1+, whereas 7 of the 12 variant translocation-carrying lines were CALLA- LB-1+. The remaining two expressed both antigens to some extent. The difference is statistically significant at the 0.03 level.

Rearrangement for the T-cell receptor gene and co-expression of immature T-cell markers and natural killer cell phenotype, in a patient with acute lymphoblastic leukaemia

We describe a patient with acute lymphoblastic leukaemia whose blasts co-expressed immature T-cell markers and nearly the entire phenotypic repertoire of NK cells. The T-cell nature of the proliferating blasts was proven by the demonstration of the rearrangement for the beta-chain of the T-cell antigen receptor. Although an abnormal phenotypic expression related to the neoplastic proliferation cannot be formally excluded, it is possible that the cells in this patient may represent the clonal expansion of a normal subpopulation of T-cell lineage NK-related cells frozen at an early stage of differentiation. These features provide arguments for discussing the controversial issue of the ontogeny of NK cells and their relationship to the T-cell lineage.

Persistence of bone marrow lymphocytosis after induction treatment in common acute lymphoblastic leukemia. Marker analysis and significance

In a series of 22 adult acute lymphoblastic leukemias expressing the common acute lymphoblastic leukemia antigen (cALLA +), eight had marrow lymphocytosis greater than 30% (43 +/- 12%) with disappearance of marrow lymphoblasts and correction of bone marrow insufficiency at the end of the induction treatment. Four of these patients were studied for the cALL antigen at this time and had persistence of this immunological marker (62 +/- 15% of the mononuclear bone marrow cells). The evolution of these patients suggests that these patients were not in complete remission and emphasizes the usefulness of cALLA determination in cases with borderline excess of marrow lymphocytes.

Molecular and immunological evidence of B-cell commitment in "null" acute lymphoblastic leukaemia

The DNA configuration of the immunoglobulin (Ig) heavy and light chain genes and the expression of B-cell-related markers were evaluated in 13 cases of non-T, non-B, non-common ("null") acute lymphoblastic leukaemia (ALL). A rearrangement of the Ig heavy-chain gene was found in all cases studied; in 5 of these a structural reorganization of the kappa or lambda light chain gene was also demonstrated. Leukaemic cells from 10 of the 13 cases analysed showed one or more B-cell antigens, the expression of which followed a sequential order of presentation (OKB2, B4, BA-1, B1). The B-cell commitment was confirmed by means of a sensitive immunoperoxidase assay which revealed a weak expression of the common ALL (cALL) antigen in 7/10 cases tested, which were all cALL-negative by conventional immunofluorescence techniques. These findings suggest that in "null" ALL the neoplastic cells show molecular and immunological evidence of B-cell differentiation and that most cases may indeed be characterized by "early" cALL with a very low density expression of the cALL antigen. This was further documented in one case in which the expression of the cALL antigen (and of other B-cell markers) could be induced after exposure to 12-O-tetradecanoylphorbol-13-acetate (TPA). The presence in a few cases of myeloid features, particularly when the cALL antigen could not be demonstrated by the immunoperoxidase assay, suggests that the leukaemic process may sometimes involve a very early progenitor cell capable of both lymphoid and myeloid phenotypic differentiation. The heterogeneity of "null" ALL documented by this study may help to explain the variable clinical course and prognosis of these patients.

Comparative studies between a new human rhabdomyosarcoma cell line, JR-1 and its tumour of origin

A new human embryonal rhabdomyosarcoma cell line, designated JR-1, is described that closely resembles the tumour from which it was derived. Comparative studies, by light and electron microscopy reveal morphological features such as myofibre formation, that are concordant with embryonal rhabdomyosarcoma. Immunohistological investigations using a panel of monoclonal antibodies indicate that the cell surface antigen profile of the JR-1 cell line is similar to other embryonal rhabdomyosarcomas. In addition the cell line expresses the cytoplasmic intermediate filament protein desmin, only found in cells of rhabdoid origin. Karyotyping JR-1 shows the cells to contain variable numbers of chromosomes (range 44-100). DNA flow cytometry indicates that cells have an DNA content which is approximately twice normal. The JR-1 cell line has a doubling time of 29 h in culture and, in common with several other human cell lines, produces xenografts in nude mice within 6 weeks of inoculation. With detailed studies on the original tumour and the JR-1 cell line, the latter should prove an excellent model system for investigating the biology of rhabdomyosarcoma.

Intracellular immunoglobulin G 'pseudocrystals' in a patient with chronic B-cell leukemia

A patient with chronic B-cell leukemia in whom the malignant lymphocytes showed intracellular inclusions of immunoglobulin (Ig) G kappa molecules is described. Electron microscopy revealed filamentous material in the nuclear envelopes and in the cisternae of the rough endoplasmic reticulum. These in vivo surface Ig-negative, nonexcreting cells could be stimulated in vitro to excrete immunoglobulin-free light chain molecules into the supernatant, which were not found in the cytoplasm after stimulation.

Immunological subclassification of non-T, non-B acute lymphoblastic leukaemia in childhood

41 cases of non-T, non-B acute lymphoblastic leukaemia (ALL) were classified by immunological criteria using a panel of monoclonal antibodies against common ALL antigen (cALLa), p24, p20 and HLA-DR antigens. Out of 41 cases, cALLa, p24, p20 and HLA-DR antigens were positive in 31 cases, 34 cases, 35 cases and 41 cases, respectively. 4 cases expressing cytoplasmic mu heavy chains were included in the group of common ALL. We demonstrated that a majority of non-T, non-B ALL would be derived from B-lineage cells. The expression of p24 and p20 was followed by the expression of cALLa and the synthesis of cytoplasmic immunoglobulin. These items of evidence support the idea that the expression of cALLa, p24, p20 and HLA-DR antigens on ALL cells would be universal in the USA, Europe and Japan. Although morphologically identical, non-T, non-B ALL cases could be subdivided into phenotypically-defined subgroups on the basis of cALLa, p24, p20 and HLA-DR antigens.

Single allelic C mu gene rearrangements in patients with T cell and undifferentiated leukemia

By using a panel of monoclonal antibodies in combination with conventional morphological and histochemical studies, seven leukemic patients were diagnosed as having T-cell lymphocytic leukemia (ALL) and three patients were classified as having acute undifferentiated leukemia (AUL). When genomic DNA from each patient was analysed by the Southern blot hybridization technique, two out of seven cases with T-cell ALL and two of three cases with AUL demonstrated immunoglobulin (Ig) mu gene rearrangements. Interestingly, the patterns of C mu gene rearrangement found in these four cases as well as in the T-cell line HSB-2 were quite similar with rearrangement of a single allele and germ line configuration retained in the other allele. Ig gene rearrangement is an essential property of cells of B-lineage, but detection of an Ig gene rearrangement by itself seems insufficient to assign commitment to B-lineage differentiation. The significance of Ig gene rearrangements in T-cell ALL is unclear, but this heterogeneity at the DNA level among T-cell ALL may reflect differences in leukemogeneis and have prognostic and therapeutic implications.

Diversity of cell surface hematopoietic antigens on K-562 sublines identified with monoclonal antibodies

The surface antigen profile of 8 sublines of K-562 cells, the original line, and the clone RA6 was determined with a panel of 12 monoclonal antibodies reactive with hematopoietic cell differentiation antigens. Cells from all sublines expressed the precursor hematopoietic antigen reactive with RFB-1, the T-cell antigen reactive with OKT17, the B cell/granulocyte antigen reactive with BA-1, the My-1 antigen, and glycophorin A which reacted with R10. A low percentage of cells in some of the sublines expressed platelet/monocyte glycoprotein I binding AN51, monocyte antigen binding 63D3, and an erythroblast/monocyte/platelet antigen binding 5F1. The use of a panel of K-562 sublines demonstrates that K-562 cells do share several "common" antigens but express a marked diversity and variability of other hematopoietic antigens.

Lineage specific classification of leukaemia: results of the analysis of sixty cases of childhood leukaemia

In addition to conventional morphological, histochemical and immunological marker studies, cells from 60 children with leukaemia were further analysed using the Southern blot hybridization technique to look at differences in the organization of immunoglobulin (Ig) genes. Of the 60 patients studied by conventional means, 47 were diagnosed as acute lymphocytic leukaemia (ALL) and 13 as non-lymphocytic leukaemia. Seven patients were initially classified as T ALL and 40 as non-T, non-B ALL. Further subclassification of the 40 patients with non-T, non-B ALL indicated three pre-B ALL and 29 patients diagnosed as common ALL, expressing Ia and CALLA antigens. All 29 patients with common ALL demonstrated C mu gene rearrangements with or without light chain (kappa and lambda) genes rearrangement. Based on the developmental hierarchy of Ig gene rearrangement, it was possible to further subclassify the patients with common ALL into different stages of B cell development. Eight (of the 40) patients with non-T, non-B ALL were identified as CALLA- but further analysis indicated T-lineage origin in two patients and three patients were reclassified as acute undifferentiated leukaemia (AUL). C mu gene rearrangements were detected in two patients with T ALL, two patients with AUL and one patient with acute myelogenous leukaemia (AML). In contrast to the patients with common ALL, Ig gene rearrangement observed in these non-B-lineage cells was restricted to a single C mu gene while retaining germ-line configuration of the other allele of the C mu gene and both light chain genes.

Expression of the common acute lymphoblastic leukaemia antigen (CALLA gp100) in the brush border of normal jejunum and jejunum of patients with coeliac disease

Expression of the gp100 common acute lymphoblastic leukaemia antigen (CALLA) was studied in the mucosa of the gut by means of indirect immunofluorescence on cryostat tissue sections with a panel of eight monoclonal antibodies to common acute lymphoblastic leukaemia antigen (anti-CALLA antibodies) and two antibodies to non-CALLA leukaemic antigens. Expression of CALLA was absent from normal stomach epithelium, adult and fetal colonic epithelium of normal histology, and colonic epithelium from patients with Crohn's disease or ulcerative colitis. By contrast, all eight anti-CALLA antibodies gave a characteristic reaction in normal adult and fetal small bowel mucosa, with specific localisation to the entire brush border of jejunal epithelium. Whereas seven of these antibodies reacted both with normal jejunal epithelium and with the damaged epithelium of patients with coeliac disease, antibody RFAL-2 reacted strongly only with histologically normal small bowel but more weakly in patients with coeliac disease to a degree related to the amount of histological abnormality. Expression of the moeity like CALLA identified with RFAL-2 was strongest in crypt epithelium and proportionally diminished along the villi according to the amount of histological damage in coeliac disease, being essentially absent in patients with "subtotal villous atrophy."

Phenotypic heterogeneity at the DNA level in childhood leukemia with a mediastinal mass

Although phenotypic heterogeneity of childhood T-cell acute lymphocytic leukemia (T-ALL) which bear receptors for sheep red blood cells (E-rosettes) and/or T-cell-associated antigens has been reported, there are certain clinical features which are shared by most patients. A mediastinal mass is one of the most characteristic presentations in this particular disorder. This report describes four children with ALL, who presented with a mediastinal mass. Three patients were E-rosette-negative and one was E-rosette-positive. Individual surface phenotypes, defined by a panel of monoclonal antibodies, were quite different. Since Ig gene organization is an essential property of cells of B-lineage, it was surprising to find that analysis of genomic DNA revealed immunoglobulin (Ig) gene rearrangements in two of them. These findings suggest that there is significant heterogeneity even among those leukemias associated with a mediastinal mass, and that a mediastinal mass may not clearly indicate origin from cells of T-lineage. This heterogeneity may reflect differences in leukemogenesis and may have prognostic and therapeutic implications.

Reactivity of rat monoclonal antibody CAMPATH-1 with human leukaemia cells and its possible application for autologous bone marrow transplantation

The rat monoclonal antibody CAMPATH-1 recognizes a hitherto undefined antigen present on virtually all normal lymphocytes and monocytes. Its reactivity with 105 samples of fresh leukaemic cells and 13 cell lines was measured by indirect fluorescence and peroxidase staining to define in more detail which stages of differentiation it recognizes. It was found to bind to cells from virtually all cases of lymphoid leukaemia (B cell CLL, T cell ALL, cALL and the few examples of HCL, PLL, Sezary syndrome and CGL in lymphoid blast crisis). The single case of cALL in relapse and four of six cases of null ALL were negative. Binding to non-lymphoid leukaemia cells (AML, AMML, AMoL, APL, AEL and CGL in blast crisis) was weaker or undetectable. Binding to established lymphoid cell lines was generally weak compared with fresh cells but some lines (MOLT4, DAUDI and X308) expressed adequate amounts of antigen to be lysed by CAMPATH-1 with human complement. Because CAMPATH-1 is very effective at killing lymphocytes in the presence of human complement, it has been used for removal of T cells in allogeneic transplants. The present results suggest that it might also have a role in purging bone marrow of leukaemia cells prior to autologous transplantation for acute lymphocytic leukaemia.

Chronic B-cell leukemias: relation between morphological and immunological features

To better understand the heterogeneity of chronic B-cell leukemias we correlated morphological and immunological features by studying the peripheral blood from 80 patients with a panel of anti-immunoglobulin and fourteen monoclonal antibodies, which hitherto were studied separately or with respect to one single morphological entity only. Of these the surface immunoglobulins (sIg) and monoclonal antibodies (McAb) BA-1, BA-2, FMC7, OKM1, and anti-T65 allowed a fair distinction between five cytological subtypes: chronic lymphocytic (CLL), "lymphoplasmacytoid" (LPL), centrocytic (CL), prolymphocytic (PLL), and hairy cell leukemia (HCL). In that order the sIg showed a decreasing number of cases of mu +/- delta class and an increase of alpha or gamma positivity. The number of BA-1-positive cases was decreased in PLL and HCL. There was a decline of BA-2- and anti-T65-positive cases in the order mentioned, while this was accompanied by an increase of FMC7 and OKM1 positivity. A significant mutual exclusion between anti-T65 and FMC7 was observed and the same was true for FMC7 and BA-2. The antibodies FMC7 and OKM1, and anti-T65 and BA-2 were linked to each other. Also FMC7 positivity was related to sIg of the alpha and gamma classes. On the basis of this unique combination of markers a differentiation scheme of B lymphocytes is proposed, in which prolymphocytic leukemia and hairy cell leukemia seem to represent a maturation arrest at a more advanced stage than chronic lymphocytic or "lymphoplasmacytoid" leukemia.

Impaired B lymphocyte reactivity in patients after radiotherapy

The effect of therapeutic irradiation upon B lymphocyte function was investigated in patients with various malignancies. The test system used was a reverse hemolytic plaque assay, which made it possible to study the activation and differentiation of B lymphocytes into immunoglobulin-secreting cells (ISC). Peripheral blood lymphocytes from normal individuals and patients before and after radiotherapy were stimulated in vitro with the polyclonal B cell activator pokeweed mitogen, and the number of ISC was estimated. B cell reactivity was markedly reduced in those patients who had received irradiation within the last six months. In patients in whom radiotherapy had been terminated more than 12 months before the lymphocytes were tested, B cell reactivity was comparable to that of patients prior to radiotherapy. By means of marker analyses, there was a reduction of B lymphocytes and T lymphocytes in the peripheral blood with a preponderance of T helper cells. Several mechanisms--e.g., reduced or defective B cell differentiation, altered regulatory T-helper or suppressor cell function or activation of suppressive monocytes--could be responsible for impaired B cell reactivity after radiotherapy.

A new set of monoclonal antibodies against acute lymphoblastic leukemia

Six monoclonal antibodies produced by immunization of Balb/c mice with common acute lymphoblastic leukemia (cALL) cells were tested against various types of normal and malignant tissues. ALB1 and ALB2 are directed to the cALL antigen (CALLA gp100); ALB6 recognizes a determinant of p24; ALB7, ALB8 and ALB9 have a pattern of reactivity similar to Ba1. None of these antibodies specifically identify cALL but they should be useful tools for diagnosis or depletion of bone marrow in autologous therapy in transplantation. In addition, the example of ALB6 which acts as a platelet aggregating agent, suggests that the study of other cell systems expressing the antigens associated with cALL may shed light on the function of these antigens and subsequently on the physiopathology of the leukemic cells.

A comparison of membrane marker phenotypes in hairy-cell leukemia and phorbol-ester induced B-cll cells using monoclonal antibodies

The neoplastic cells from 14 cases of hairy-cell leukemia were investigated in order to determine their membrane phenotype on the basis of their reactivity with a large panel of B-, T-, myeloid/monocytic- and non-lineage restricted monoclonal antibodies. The data were compared to those from monoclonal antibody studies on phorbol-ester (TPA) induced cells from 10 patients with B-type chronic lymphocytic leukemia. The study has so far revealed further evidence for the B-cell nature of hairy-cells leukemia and demonstrates a developmental link between the two cell types, suggesting that hairy-cells represent a more advanced differentiation stage along the B-cell lineage.

In vitro drug testing using hemopoietic cells: goals and limitations

In vitro drug sensitivity is one of many biologic variables which may predict in vivo drug response. Even if in vitro assays provide relevant data, for some tumors, variable levels of stem-cell origin, differentiation, tumor heterogeneity, or self renewal may be more important than cytotoxicity to proliferating cells. Although ANLL has been used here frequently as a model, it may not be the most appropriate tumor for study. Unlike many cancers, in ANLL, primary drug resistance is unusual, and in relapse, secondary drug resistance is usually incomplete. It has been suggested that in vitro drug sensitivity predicts remissions for patients who do not die of infection or remain aplastic during induction therapy. However, for the majority of patients, this argument acknowledges the overriding importance of biologic variables other than in vitro drug cytotoxicity. For rapidly growing tumors, such as Burkitt's lymphoma, rapid emergence of drug resistance related to disease burden may be the most important response determinant. Perhaps in other tumors, in vitro drug sensitivity will be an independent variable of overriding importance. To determine the role of in vitro drug testing, trials examining in vitro drug sensitivity must meet stringent criteria. The assays should use well-defined and reproducible cultures and drug exposures. The trials must be large enough, contain homogenously treated patients, and use carefully defined response and survival endpoints. Decision rules derived from such trials must be further tested by prospective evaluation. Investigators conducting these trials must be prepared to search for important in vitro results reflecting tumor biology and to analyze in vitro drug sensitivity as only one continuous variable determining in vivo responses. Such trials will be difficult to conduct and expensive. In the final analysis, in vitro assays may find their most important roles as preclinical drug screens and models for in vitro drug resistance. Further insights into molecular genetics of malignant transformation and drug resistance may make such assays obsolete, but for the present, they provide important insights into tumor variability and mechanisms of drug response.

Chromosome mapping of cell membrane antigens expressed on activated B cells

Hybrids formed by fusion of either human acute lymphoblastic or chronic lymphocytic leukemia cells and the mouse myeloma P3.X63.Ag8/653 have been used to show that the expression of two cell surface antigens, Bp37 and p76, associated with B cell activation and detected by the monoclonal antibodies BB1 and BB2, respectively, segregate with human chromosomes 12 and 19, respectively. Another antigen expressed on activated B cells (p24) also maps to chromosome 12 (Katz et al., Eur. J. Immunol. 1984. 13: 1008) which is of interest in the light of the frequent involvement of this chromosome in certain B cell leukemias and lymphomas.

Isoenzyme studies in human leukemia-lymphoma cell lines--1. Carboxylic esterase

The isoenzyme patterns of carboxylic esterase (E.C. 3.1.1.1) were studied in 74 proven human leukemia-lymphoma and 12 normal B-lymphoblastoid cell lines. These cell lines have been extensively phenotyped using poly- and monoclonal antibodies. Esterase isoenzymes were separated by isoelectric focusing and visualized by histo-cytochemical techniques. No leukemia-specific or (except for monocytes) blood cell type-specific isoenzyme or isoenzyme pattern could be detected. The monocytic element in some cell lines was characterized by a strong isoenzyme band which could be selectively and completely inhibited by sodium fluoride. The enzyme phenotypes were stably expressed in all subcultures of a given cell line and did not appear to have any cell cycle dependency. The leukemia-lymphoma cell lines have been subclassified into four major groups according to immunological parameters: T-cell, B-cell, myelomonocytic and non-T, non-B-cell. On the basis of immunological data the T-cell lines were assigned to five stages of differentiation. The number and staining intensity of the isoenzymes increased with differentiation of the T-cells paralleling the expression of immunological markers. The B-cell leukemia-lymphoma cell lines were divided into pre B-, B-, Burkitt lymphoma, multiple myeloma and hairy cell leukemia cell lines. Substantial variability among the isoenzyme patterns was detected ranging from immature profiles of pre B-cell lines to complete isoenzyme repertoires of multiple myeloma cell lines. No significant difference was seen between the isoenzymes of mature B-cell lines and normal B-lymphoblastoid cell lines. The most prominent feature seen in myelomonocytic cell lines was the monocytic band indicating a monocytic origin and separating the 'monocytoid' from the 'pure myeloid' cell lines. Considerable heterogeneity in the isoenzyme patterns was observed in the non-T, non-B cell groups which comprised erythroleukemia cell lines and cell lines arrested at a very early stage of lymphoid differentiation. These latter cell lines together with some T- and B-cell lines shared the common characteristics of positivity for cALLA, TdT and Ia antigens and an immature, incomplete isoenzyme profile. The results support the notions of maturation arrest and normal gene expression in leukemic cell populations. Furthermore, the importance of biochemical studies as part of the multiple marker analysis could be demonstrated.

Different stages of B cell differentiation in non-T acute lymphoblastic leukemia

Immunoglobulin heavy chain gene rearrangement was evaluated in 19 cases of acute lymphoblastic leukemia (ALL) and correlated with the immunological phenotypic expression on primary or phorbol diester (12-O-tetradecanoylphorbol-13-acetate [TPA])-induced cells. One case of common ALL (cALL), one case of T-ALL, and one undifferentiated acute leukemia that responded to anti-myeloid drugs after unsuccessful anti-lymphoid induction therapy, had germ line heavy chain genes. Rearranged immunoglobulin genes were instead found in 15 of the 16 cALL cases studied and in a case of non-T, non-B, non-common ("null") ALL, which suggested the B cell origin of the neoplastic cells. All cases bearing a heavy chain gene rearrangement were HLA-DR positive. However, the unique cALL case with a germ line configuration was also HLA-DR positive, which confirmed that both the cALL antigen and HLA-DR antigen were not per se expression of B cell commitment. On the other hand, a complete search for B cell-related markers (BA-1 and B1 monoclonal antibodies, as well as cytoplasmic immunoglobulins [CyIg]) in the cALL cases showed that at least one B cell marker could be detected either on primary or on TPA-induced cells in all cases in which a gene rearrangement had occurred. Incubation with TPA allowed the detection of one B cell marker in a case in which the primary cells were negative, and increased the expression of B cell markers in all but one of the cALLs tested. The only cALL case that was not rearranged expressed no B cell markers either on primary or on TPA-induced cells. The non-T, non-B, non-common ("null") case that was rearranged also showed no phenotypic evidence of B cell markers on primary and induced cells. These findings indicate that: (a) practically all cases of cALL appear to be of B cell origin as shown by gene rearrangement analysis; (b) DNA studies are relevant for a more precise characterization of individual cases of undifferentiated acute leukemia; (c) a complete survey for B cell markers may establish the B cell origin of the cALL blasts, as long as the analysis on primary cells is complemented by differentiation induction assessment; and (d) most cases of non-T ALL appear to be characterized by the expansion of neoplastic cells "frozen" at different levels along the B cell differentiation pathway, the first detectable marker being heavy chain gene rearrangement, followed by BA-1, B1, and CyIg expression.

Augmentation of mixed lymphocyte response. Stimulatory activity by phorbol ester

The tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) induces a variety of phenotypic changes on normal and malignant cells. In chronic and acute lymphocytic leukemia we have observed a marked augmentation in mixed lymphocyte reaction stimulatory capacity (MLRs) following pretreatment of leukemia blasts with TPA. We have now characterized the effects of TPA on MLRs utilizing the non-T, non-B lymphoblastic leukemia-cell line, HOON. Following pretreatment with TPA (optimal concentration, 1.6 X 10(-10) M), but not with other phorbol esters, there was a marked increase in MLRs, particularly at lower stimulator-cell concentrations. This effect was maximal following a 44-hr preincubation period and the enhancement in MLRs was not accompanied by changes in levels of Ia expression. This cell line provides a model for determining the molecular basis for the TPA-induced augmentation of stimulatory capacity in the mixed lymphocyte reaction.

Immunoglobulin mu-chain gene rearrangement in a patient with T cell acute lymphoblastic leukemia

A 6-yr-old girl with T cell acute lymphoblastic leukemia (ALL) is described. She had a mediastinal mass and her leukemic cells expressed T cell-associated antigens (Leu 1+, OKT3+, OKT9+, and OKT10+). When we examined genomic DNA from the leukemic cells, we detected Ig mu-chain gene rearrangement with germ-line configuration of light chain genes. As reported recently, detecting Ig gene rearrangement has become an important procedure for further classifying B cell precursor cells. This case, however, suggests that there is also heterogeneity among patients with T cell ALL, not only at the level of cell surface phenotypes, but also at the level of the Ig gene. These findings have major implications when we consider both the ontogenesis of these leukemic cells and the normal differentiation of human lymphocytes.

Diagnostic specificity of the monoclonal anti-CALLA antibody VIL-A1 in leukemia and malignant lymphoma

VIL-A1 is an anti-CALLA antibody which binds efficiently and exclusively to CALLA positive cells. When the cell type specificity of VIL-A1 is studied in acute leukemias and lymphomas, results show that in those leukemias which could be characterized by cytochemical and morphological methods, VIL-A1 reactivity was specific for cells of lymphoid origin. It can therefore be assumed that VIL-A1 positive AUL cells (in this case 4 out of 9 patients) are also lymphoid in origin. In no case were AML blasts found to be positive with this antibody. Seventy-four per cent of the 88 ALL patients were positive (L1 + L2) whereas none in the L3 subgroup were positive, and 48% of CML patients in blastic crisis were positive. Of the low grade non-Hodgkin malignancies, only CB/CC was positive, distinguishing it from the CC type which was negative. Of the high grade lymphomas IB was found to be negative, while the others showed a heterogeneous picture which was not related to other immunological parameters.

Heterogeneity of non-T, non-B acute lymphocytic leukemia defined by the quantitative expression of Ia and common all antigens

The Ia antigens and the common acute lymphoblastic leukemia antigens (CALLA) accessible on the cell surface were quantitated in newly diagnosed patients with non-T, non-B ALL using monoclonal antibodies and a cellular radioimmunoassay. The levels of both antigens expressed in molecules of RAM-Fc bound per cell exhibited a wide range of variation amongst patients. Ia levels, measured with monoclonal antibody 21w4 which recognizes a monomorphic epitope of human Ia molecules, were between 5.0 X 10(4) and 87 X 10(4) molecules per cell in 37 patients. CALLA levels measured with BA-3 or J-5 antibody varied from 3.4 X 10(4) to 22 X 10(4) molecules per cell in 13 patients. In 12/13 cases for which Ia and CALLA were quantitated simultaneously, the amount of Ia was found to be higher than that of CALLA. A positive correlation (p less than 0.02) between the levels of these two antigens was observed suggesting that ALL cells with the highest levels of Ia also had the highest levels of CALLA. In addition, our results suggest a possible correlation (0.05 less than p less than 0.1) between the amount of Ia expressed on the leukemic cells and the white blood cell count of the patient at the time of diagnosis. The data indicate that non-T, non-B ALL are heterogeneous with respect to their expression of Ia and CALLA antigens. A longitudinal study of non-T, non-B ALL patients will allow us to assess if the levels of Ia and CALLA at diagnosis are correlated with prognosis of the disease in these patients.

Differentiation-associated changes in human non-T, non-B leukemia cell lines after treatment with 12-O-tetradecanoylphorbol 13-acetate (TPA)

The ability of TPA to induce stable phenotypic changes that normally serve as markers of differentiation was examined in the four human non-T, non-B cell lines, NALL-1, NALM-16, REH and KM-3. In all four lines, noncytotoxic concentrations of the phorbol ester caused an extensive reduction in the number of cells expressing cALL surface antigen and terminal deoxynucleotidyl transferase. The disappearance of these markers correlated with the loss of cell proliferation. In one of the cell lines, NALL-1, TPA treatment gave rise to a significant increase in Ia-like antigen and antigen T-101, markers which represent more advanced stages of cell maturation. However, surface or cytoplasmic immunoglobins, indicators of mature B cells, were not detectable. Antigen 3A1, specific for myeloid and for T cells, antigen Leu-4, specific for T cells and antigen CM1, specific for monocytes, were also absent. In all cell lines, exposure to TPA resulted in an approximately two-fold increase in acid phosphatase and beta-glucuronidase activity. The emergence of these phenotype changes was not altered upon repeated washing of the TPA-treated cells. These results demonstrate that while TPA is capable of inducing various non-T, non-B cell lines to differentiate to a limited degree, differences exist between the lines in the extent to which they can mature towards the B-cell stage.

Characterization of new non-T, non-B acute lymphoblastic leukemia cell lines: analysis of surface antigens by quantitative cellular radioimmunoassay and flow cytometry

Two novel acute lymphoblastic leukemia (ALL) cell lines, HOON and HYON, have been established from patients with non-T, non-B ALL. The cell lines have been characterized and shown to express phenotypic markers on non-T, non-B ALL. By indirect immunofluorescence and flow cytometry they express Ia and common ALL (CALLA) antigens and are reactive with monoclonal antibodies BA-1, BA-2 and OKT-9. However, the cells do not express detectable amounts of B1 antigen or of cytoplasmic mu chain, which are markers of pre-B cells. Quantitation of Ia and CALLA antigens on HOON and HYON cell lines using a cellular radioimmunoassay revealed that both cells bind high levels of anti-Ia antibodies, 110 X 10(4) molecules per cell, and low levels of anti-CALLA antibodies, 7 X 10(4) molecules per cell. Although both HOON and HYON carry equivalent amounts of Ia on their surface, only the former is a good stimulator of the one-way mixed lymphocyte reaction.

Lymphocyte subsets in the peripheral blood of patients with multiple myeloma and benign monoclonal gammopathy

A panel of monoclonal antibodies that identify various antigens present on T and B cells was used to characterize circulating blood lymphocyte subsets in multiple myeloma [(MM)--13 patients] and benign monoclonal gammopathy [(BMG)--5 patients]. In MM and BMG an increase in B cell proportions (BA 1 positive cells) was observed, whereas T cells (Lyt 3 positive cells) were reduced compared to normal controls. However, with respect to the T cell subset distribution, a marked diversity between MM and BMG was noted. This may help to differentiate BMG from MM. In MM a relative decrease in inducer/helper T cells (OKT 4 positive cells) and increase in suppressor/cytotoxic T cells (OKT 8 positive cells) as well as in NK/K T cells (Leu 7 positive cells) was observed. On the other hand, in BMG the relative T cell subset distribution was comparable to those seen in normal subjects.

Construction of an antigenic map for human B-cell precursors

The purpose of this study was to evaluate the binding of a panel of monoclonal antibodies to human pre-B cells present in fetal, pediatric, and adult bone marrow. The antibodies included BA-1, BA-2, BA-3 (anti-CALLA), anti-B1, L243 (anti-HLA-DR), and T101. Binding of the monoclonal antibodies to pre-B cells was evaluated at the single-cell level by double fluorochrome analysis. Percentages of BA-1+ and anti-B1+ pre-B cells were independent of age group. BA-1 bound to approximately 80% of fetal, pediatric, and adult bone marrow pre-B cells, whereas anti-B1 bound to approximately 50%. BA-2 bound to 55% of fetal pre-B cells, but this percentage decreased to 32% in pediatric and 16% in adult bone marrow. CALLA was expressed on less than 10% of fetal, pediatric, and adult bone marrow pre-B cells, and HLA-DR was expressed on greater than 95% of fetal, pediatric, and adult pre-B cells. Although T101 (an anti-T-cell monoclonal antibody) did not bind to pre-B cells, it did bind to approximately 25% of the sIgM+ cells in fetal bone marrow. These results suggest a predominant phenotype of L243 (anti-HLA-DR)+, BA-1+, BA-3 (anti-CALLA)-, T101- for the human pre-B cell while phenotypic heterogeneity exists for anti-B1 and BA-2.

Polymorphonuclear neutrophils express the common acute lymphoblastic leukemia antigen

Monoclonal antibodies J5, VIL-A1, and BA-3, known to react with the common acute lymphoblastic leukemia antigen (CALLA) were found to specifically stain normal human polymorphonuclear neutrophils (PMN). The antigen detected on PMN had a molecular weight (95,000-110,000 mol wt) close to that of CALLA (95,000-100,000 mol wt) and thus these surface membrane antigens are likely related, if not identical. The fluorescent staining intensity of PMN is comparable to that of CALLA-positive leukemic cells and the presence of PMN in patient samples could potentially produce false-positive results in diagnosis.

Serological analysis of cell surface antigens of HL-60 cells before and after treatment with a phorbol ester tumor promoter

The human HL-60 cell line derived from acute promyelocytic leukemia, consisting of promyelocytic type of cells, was able to differentiate into adherent cells with monocytemacrophage features by the treatment with 12-0-tetradecanoyl phorbol-13-acetate (TPA). Cell surface antigens of HL-60 cells before and after TPA treatment were studied with monoclonal antibodies and four hybridoma clones producing IgM antibodies were established. Two antibodies (HL-21 and HL-47) reacted only with the immunizing TPA-treated HL-60 cells, and HL-1 antibody produced against untreated cells was reactive with both TPA-treated and untreated cells, but HL-5 antibody reacted predominantly with the immunizing untreated cells. Serological reactivity against various types of normal hematopoietic cells and acute leukemias (diagnosed by the French-American-British classification) was studied by immune adherence assay and immuno-electron microscopy. HL-21 antibody was reactive with monocytes and most cases of M4 and M5 types of acute non-lymphocytic leukemia cells. HL-47 antibody did not react with the cells of myelocyte-monocyte lineage or mature lymphocytes, but it did react with one-third of acute lymphocytic leukemia (L1 and L2) cases. Since all HL-47+ cases were included in the group of common ALL antigen positive cases, it was estimated that HL-47 is a differentiation antigen present on lymphocyte precursors, from which null-cell type acute lymphocytic leukemia cells generally originate. HL-1 antibody reacted with the cells of myelocyte-monocyte lineage as well as those of most acute non-lymphocytic leukemias. HL-5 antibody reacted with granulocytes and M2 type of acute myelocytic leukemia cases, and also with M5 type of acute monocytic leukemia cases. Serological studies of these antibodies revealed that TPA can induce to differentiate HL-60 cells not only into HL-21+ macrophage-like cells, but also into HL-47+ lymphoid stem cells. In addition, these antibodies were demonstrated to be very valuable for differential diagnosis of acute leukemias.

Monoclonal antibodies directed against human lymphoid, monocytic, and granulocytic cells: reactivities with other tissues

Monoclonal antibodies (MAbs) reactive with lymphoid cells are not necessarily specific for lymphoid tissues. Forty MAbs with varying degrees of specificity in lymphoid tissue were tested against a wide battery of nonlymphoid human tissues. Cross-reactivity was identified in 18 of 41 antibodies tested. Based on their reactivities, the MAbs were classified in three groups: (1) antibodies with wide reactivities in normal nonlymphoid tissues, i.e., anti-Leu 4, anti-Leu M1, OKT9, anti-HLA-Dr, anti-Leu M2, Mo-2 (Coulter), anti-Leu 7, BA-1, BA-2, BA-3, J5, and A1G3; (2) antibodies with limited reactivities in nonlymphoid tissues (one or two tissues), i.e., OKT6, anti-Leu 10, Mo-1 (BRL), Mo-2 (BRL); and (3) antibodies without cross reactivities in nonlymphoid tissues, i.e., anti-Leu 1, anti-Leu 2a, anti-Leu 3a, OKT3, OKT10, 3A1, anti-Leu 8, TA-1, Lyt 3, B1, B2, OKMo-1, anti-Leu M3, T200. The reactions can be attributed to the presence of a similar, if not identical, epitope in related or different molecules.