Biophysical characterization of GB virus C from human plasma.

Viral characterization studies were carried out on GB virus C (GBV-C) RNA positive plasma from normal human donors and from donors co-infected with GBV-C and hepatitis C virus (HCV). GBV-C RNA was detected by reverse-transcriptase polymerase chain reaction (RT-PCR) and probe hybridization in a single tube assay. Sequential filtration of GBV-C positive plasma indicated that GBV-C RNA is associated with a particle 50-100 nm in diameter. The peak of GBV-C RNA in sucrose gradients was observed at a buoyant density of 1.05-1.13 g/ml. GBV-C RNA titer was reduced following treatment with chloroform or with five detergents indicating that GBV-C has a lipid-containing envelope. Sucrose density gradients and self-forming cesium chloride gradients of detergent-treated GBV-C showed a shift in the RNA peak to heavier buoyant density only when RNase inhibitor (RNasin) and high detergent concentrations were present. The treated material was non-filterable and the RNA had a density of > 1.5 gm/ml.

Seroprevalence of GB virus C and persistence of RNA and antibody.

Exposure to GB virus C (GBV-C) was determined in several U.S. populations by both reverse-transcription-polymerase chain reaction (RT-PCR) and by an enzyme linked immunosorbent assay (ELISA) for antibodies to mammalian cell-expressed GBV-C envelope protein, E2 (GBV-C E2). Most individuals exposed to GBV-C were either RNA positive/ELISA negative or ELISA positive/RNA negative. Exposure, therefore, was measured as the sum of GBV-C RNA positive and GBV-C E2 antibody positive specimens, and was higher in commercial plasmapheresis donors (40.5%) than in volunteer blood donors (5.5%). In intravenous drug users (IVDUs), GBV-C exposure was 89.2%. Serial bleed specimens tested for GBV-C RNA indicate that some patients remain viremic for at least 3 years and fail to produce detectable antibodies to GBV-C E2. In other exposed individuals who tested negative for GBV-C RNA, antibodies to E2 appear to be similarly long-lived (greater than 3 years) with a fairly constant titer (ranging in reciprocal endpoint dilution from 336 to 21,504). Since the detection of GBV-C RNA and GBV-C E2 antibody are mutually exclusive in most exposed individuals, studies pertaining to incidence and prevalence of GBV-C infection require both antibody and nucleic acid detection.

An optimized antibody-chelator conjugate for imaging of carcinoembryonic antigen with indium-111.

A monoclonal antibody to carcinoembryonic antigen showing minimal cross-reactivity with blood cells and normal tissues was derivatized with benzylisothiocyanate derivatives of EDTA and DTPA. Seven chelators per immunoglobulin could be incorporated without loss of immunoreactivity. The resulting conjugates, labeled with indium-111, showed low liver uptake in animals. A cold kit, comprising the DTPA conjugate at a molarity of antibody bound chelator exceeding 1 x 10(-4) M, gave radiochemical yields of indium labeled antibody of greater than or equal to 95% and was stable for 1 yr.

Chromosomal translocations play a unique role in influencing prognosis in childhood acute lymphoblastic leukemia.

Certain types of chromosomal abnormalities have been shown to exert strong independent influence on treatment outcome in acute lymphoblastic leukemia (ALL). To identify the changes most closely associated with prognosis, we analyzed the completely banded blast cell karyotypes of 161 children with this disease. One hundred twenty-five cases had one or more chromosomal abnormalities, with 45 showing translocations. The frequency of translocations was highest (58%) among patients with pseudodiploid karyotypes and lowest (0%) in the hyperdiploid group defined by 51 or more chromosomes. During the maximum 6-year follow-up period, 30 of the 45 patients with a translocation failed therapy, compared with only 27 of the 116 who lacked this feature. Life-table estimates of event-free survival indicate that only 14% of the translocation group will be in complete remission at 3 years. The percentages of failures associated with random and nonrandom translocations were virtually identical (68% v 65%). When entered in a Cox proportional hazards model with seven other types of chromosomal abnormalities, and then with 11 clinical and laboratory variables of known prognostic value in ALL, translocation emerged as the strongest single predictor of treatment outcome (P less than 0.0001). The model indicated that translocation increases the risk of treatment failure six times by comparison with the absence of this feature. These findings offer an explanation for the majority of early treatment failures in childhood ALL, including those previously attributed to ploidy classification.

Cytogenetic features and serum lactic dehydrogenase level predict a poor treatment outcome for children with pre-B-cell leukemia.

Leukemic cells from 89 (24%) of 369 children with newly diagnosed acute lymphoblastic leukemia (ALL) were found to have a pre-B immunophenotype. By comparison with blasts having the common ALL phenotype, the pre-B cells were more likely to have a DNA index less than 1.16 (P = 0.02), a pseudodiploid karyotype (P less than 0.001), and a chromosomal translocation (P = 0.001). Increased serum lactic dehydrogenase levels (P = 0.001) were also characteristic of pre-B ALL; otherwise, the clinical and laboratory features of the two groups were similar. A nonrandom chromosomal translocation, t(1;19)(q23;p13.3), was identified in blast cells from 16 (23%) of the 70 patients with pre-B ALL and adequate chromosome banding studies; different translocations were found in 11 of the remaining patients. The presence of any chromosomal translocation in the pre-B group was significantly related to a higher leukocyte count, an increased level of serum lactic dehydrogenase, an increased percentage of S-phase cells, black race, and a blast cell DNA index less than 1.16. Four presenting features were found to confer an increased risk of treatment failure among pre-B patients: pseudodiploidy, chromosomal translocation, black race, and higher serum lactic dehydrogenase level. In a multivariate analysis, pseudodiploidy emerged as the strongest factor for predicting relapse in pre-B ALL. The frequent association of chromosomal abnormalities of known adverse prognostic significance and high serum lactic dehydrogenase levels with pre-B-cell ALL explains, at least in part, the poor treatment outcome reported for children with this subtype of leukemia.

Biologic and prognostic significance of the presence of more than two mu heavy-chain genes in childhood acute lymphoblastic leukemia of B precursor cell origin.

We examined the arrangement of the mu heavy-chain immunoglobulin (Ig) genes in the leukemic blast cell DNA of 93 children with acute lymphoblastic leukemia (ALL). All cases met morphologic and cytochemical criteria for ALL, lacked detectable T cell surface antigens, and expressed HLA-DR (Ia) antigens. Eighty-three of the 93 patients (89%) were positive for the common acute lymphoblastic leukemia antigen (CALLA), and 20 of 91 (22%) tested had detectable cytoplasmic immunoglobulin. As expected, the heavy-chain lg gene was rearranged in all cases, and the pattern of rearrangements was variable; 23 had one allele rearranged and one in the germ line configuration; 15 had one rearranged and one deleted; and 37 had two rearranged. Unexpectedly, in 18 patients the presence of more than two mu gene-hybridizing bands was detected. Combinations of enzymes and heavy-chain gene probes were used to confirm that the extra bands were not the result of underdigestion of the DNA or DNA restriction site polymorphism. In eight of the 18 patients, we identified an extra chromosome 14 as a possible cause of the extra bands' hybridizing to the mu heavy-chain constant-region probe. In the remaining ten patients, the presence of three or four bands hybridizing with the mu probe suggests the presence of two populations of leukemic cells that may have arisen either by separate leukemic transformation events or by clonal evolution of one clone into two related lines. Although preliminary (2-year follow-up), our data suggest that childhood ALL of B lineage with more than two mu heavy-chain genes, but without extra copies of chromosome 14, may be more resistant to therapy.

Unfavorable presenting clinical and laboratory features are associated with CALLA-negative non-T, non-B lymphoblastic leukemia in children.

Twenty-four (5.7%) of 424 children with newly diagnosed acute lymphoblastic leukemia (ALL) were found to have blast cells that expressed HLA-DR antigens but not the common ALL antigen (CALLA), E-rosette receptors, T-cell antigens, or cytoplasmic or surface immunoglobulins. Each of the eight cases tested expressed the B-cell associated antigen B4, but not B1 or B2 antigen. Myeloid-associated antigens were not present in any of the 10 cases tested. By comparison with common (CALLA+ B-cell precursor) ALL, patients having this immunophenotype were more likely to be children less than 2 yr of age (p less than 0.001), to have higher initial leukocyte counts (p less than 0.001), and to have blast cells with a DNA index less than 1.16 (p = 0.05), a pseudodiploid karyotype (p = 0.01) and a chromosomal translocation (p = 0.003). The presence of any chromosomal translocation in these CALLA- ALL was related to measures of increased leukemic cell burden including higher leukocyte counts, larger liver and spleen sizes and higher serum lactic dehydrogenase levels. While the patients were entered into several treatment arms of two protocols, the CALLA- cases appeared to have lower remission rate (p = 0.06) and shorter event-free survival time (p = 0.05) than did those with common ALL. The association with clinical and laboratory features of known adverse prognostic significance provides some explanation for the poor treatment outcome of CALLA- ALL.

Periodic acid-Schiff stain in childhood acute lymphoblastic leukemia: lack of independent prognostic value.

The authors reviewed 250 consecutive children with ALL to determine if the periodic acid-Schiff (PAS) score was a useful, independent predictor of time to failure. PAS stains were scored from 0 to 400 and divided into low- and high-score groups using a variance-ratio test (F test) to optimize any effect of PAS on prognosis. Although the effect of PAS score considered alone approached significance for time to failure, the PAS score lost all significance when the patients were divided into standard-risk and high-risk groups on the basis of peripheral white count, central nervous system involvement, mediastinal mass, or E-rosette positivity at diagnosis. A Cox regression analysis was performed on a subgroup of 198 patients for whom cytogenetic studies were also available. The PAS score again approached the level of significance when considered alone but was of no significance after the effects of peripheral white count, pseudodiploidy, mediastinal mass, and E-rosette positivity were removed. The authors conclude that the PAS stain has no independent prognostic significance in childhood ALL.

Immunoperoxidase determination of terminal deoxynucleotidyl transferase in acute leukemia using PAP and ABC methods: experience in 102 cases.

Immunoperoxidase (IP) and immunofluorescence (IF) technics for the detection of terminal deoxynucleotidyl transferase (TdT) were applied to 102 cases of acute leukemia to compare their relative usefulness in the diagnosis and classification of acute leukemia. Two different IP technics were used, peroxidase-antiperoxidase (PAP) on 50 cases, avidin-biotin-peroxidase complex (ABC) on 42 cases, and both PAP and ABC on ten cases. Using 40% TdT+ cells to define positivity, 71 of 102 cases were IP+/IF+, 12 were IP+/IF-, and 19 were IP/IF-. The finding of 12 IP+/IF- cases suggests greater sensitivity of the IP method in detecting TdT+ acute leukemia. This greater sensitivity was demonstrated by both PAP and ABC technics. Direct comparison of ABC and PAP technics in ten cases showed the results by both methods to be similar. In addition, previous reports utilizing the IF method found approximately 10% of cases of AML to have greater than 10% TdT+ cells. The authors' findings for the IF method were similar (15%), but using the IP methods, the authors were able to detect greater than 10% TdT+ cells in 46% of AML cases and greater than 40% TdT+ cells in 31% of AML cases. The authors conclude that the IP technics for the detection of TdT offer several advantages and may be more sensitive relative to the IF method. Further, either the PAP or the ABC method is suitable for routine use in hematopathology laboratories.

Quantitative variation of the common acute lymphoblastic leukemia antigen (gp100) on leukemic marrow blasts.

Marrow blasts from children with B cell precursor acute lymphoblastic leukemia (ALL) were studied for differences in quantitative expression of the common ALL antigen (CALLA). Of 42 untreated patients, 35 had detectable amounts of CALLA by flow cytometric (FCM) analysis of J-5 monoclonal antibody binding. Using an FCM technique that provides correlated measurements of a given cell surface antigen, cell size, and DNA content, we detected increased CALLA expression as lymphoblasts moved from G0/G1 phase through S phase of the cell cycle. The density of the antigen (per unit of blast surface area) remained relatively constant over the same interval, indicating that the change was not due to S phase-specific enhancement of CALLA expression. Eight cases had hyperdiploid cellular DNA content and in seven of these, only cells with clonal abnormalities of DNA content expressed the CALLA marker. Mean amounts of CALLA for each patient ranged widely within the study group, from very high to marginally detectable. This variation had no discernible relation to cell size, stem-line DNA content, percentage of cells in S phase, or the presence or absence of cytoplasmic immunoglobulin. Results of a univariate proportional hazards analysis showed that both quantitative level of CALLA for S phase cells (P = 0.048) and white blood cell count (P = 0.012) had made significant contributions to treatment outcome. Patients with relative amounts of CALLA less than the median value for the entire CALLA+ group had a higher rate of failure, which was virtually identical to that for the seven HLA-DR+ patients whose blasts lacked detectable CALLA. The observed interpatient variation in quantitative expression of CALLA is consistent with recognized steps in B cell precursor differentiation and may be useful in distinguishing patients with a less favorable prognosis.

Evidence for clonal evolution in pre-B-cell leukaemia.

This case study provides evidence for clonal evolution in pre-B-cell leukaemia. At diagnosis, the lymphoblasts from a 3-year-old boy were morphologically subtyped as L1 (French-American-British classification). Their immunophenotype was CALLA+, CIgM+, SIg-, TdT+, and the karyotype was pseudodiploid with a 1;19 translocation. Striking shifts were apparent when the child relapsed 16 months later. The morphologic subtype had changed to L3, CALLA and TdT had disappeared, and a consistent karyotype was lacking. The modal chromosome number had increased through clonal evolution to 85, the 1;19 translocation was retained, and a new marker, a 14q+ (partial duplication) appeared and was present in a majority of cells. These cytogenetic findings are characteristic of a transforming state. However, despite the loss of TdT, the appearance of classic L3 morphology and the acquisition of a 14q+ marker, the cells retained a predominantly pre-B phenotype.

Some fixation reagents reduce or abolish the detectability of Ia-antigen and HLA-DR on cells.

The effect of paraformaldehyde (PF), glutaraldehyde (GT), methanol (ME), ethanol (ET) and acetone (AC) fixation on the detectability of Ia antigens on murine and rat peritoneal exudate (PE) and resident peritoneal (RP) macrophages (M phi), and on detectability of HLA-DR antigens on human blood leukocytes (HBL) and human splenic M phi (HSM phi) was examined. Ia-antigen on Mø from H-2k mice was detected by a rosetting assay using erythrocytes (E) to which a monoclonal antibody (MoAb) reactive to Ia.2 (E anti-Ia.2) had been coupled, and by the direct binding of 125I-labeled anti-Ia.2. The antigen was detected on Wistar/Furth (W/Fu) rat RPMø splenocytes (SC) by rosetting with E coupled with a MoAb to the murine determinate Ia.17, which cross-reacts with an Ia-like molecule on cells from the W/Fu strain. HLA-DR framework determinants were detected on HBL and HSMø by the binding of 125I-labeled MoAb and by an avidin-biotinylated peroxidase procedure. Exposure of murine PEMø or RPMø to 1% PF or 0.5% GT for 15 min at room temperature reduced 125I-anti-Ia.2 binding and E anti-Ia.2 rosetting by at least 60%; the radioimmunoassay was more affected by the fixatives than was the rosetting assay. Further, PEMø were more sensitive to the effect of PF fixation than were RPMø. Treatment of freshly isolated RPMø with 1% PF reduced the proportion of Ia-bearing cells detected by the rosetting assay by greater than 50%. Culturing alone did not affect the detectability of Ia on RPMø as assessed by the rosetting test, but cultured RPMø were more sensitive to the effects of FX fixation than fresh cells except when lymphokine from Con A-stimulated murine SC was included in the culture medium. Similar losses of HLA-DR were recorded when HBL and HSMø were exposed to PF, GT, ME or ET, but brief (less than 20 s) treatment with cold AC did not appreciably reduce antigen detectability. Procedures in which fixation takes place after the primary antibody binding step did not result in an appreciable loss of detectable Ia. Thus, commonly used fixatives affect the detectability of Ia and Ia-like antigens on a variety of cells. Results obtained from assays on cells treated prior to the primary antibody binding step, therefore, must be interpreted with caution.

New chromosomal translocations correlate with specific immunophenotypes of childhood acute lymphoblastic leukemia.

Cytogenetic analysis of leukemic cells obtained at diagnosis from 122 patients with childhood acute lymphoblastic leukemia (ALL) disclosed chromosomal translocations in 36 cases. Two new nonrandom translocations were identified and found to be associated with specific immunophenotypes of the disease. The first, identified in 4 of 16 cases of T-cell ALL positive for sheep erythrocyte receptors (E+), involved the short arm (p) of chromosome 11 and the long arm (q) of chromosome 14 and was designated t(11;14) (p13;q13). The second, found in 7 of 23 cases with a pre-B-cell phenotype, involved the long arm of chromosome 1 and the short arm of chromosome 19; it was designated t(1;19) (q23;p13.3). A third abnormality involving a common breakpoint on chromosome 12 (band p 12) was also identified. These two new differentiation-specific translocations suggest a mechanism for aberrant expression of genes that influence lymphoid cell growth and development, as well as leukemogenesis.

A monoclonal antibody (SJ-9A4) to P24 present on common alls, neuroblastomas and platelets - I. Characterization and development of a unique radioimmunometric assay.

We report the development and characterization of SJ-9A4, a monoclonal antibody (MoAb) produced against common acute lymphoblastic leukemia (C-ALL) cell lines. SJ-9A4 reacted with C-ALL, B-cell chronic lymphocytic leukemia (B-CLL), platelets and C-ALL neuroblastoma (NB) and the K562 cell lines. It had no significant reactivity with erythrocytes, granulocytes, circulating T or B lymphocytes, monocytes, granulocytic cell lines or a Ewing's sarcoma cell line. SJ-9A4 was shown to recognize the same region as two other MoAb to the p24 antigen, BA-2 and DU-ALL-1, as demonstrated by their ability to inhibit the binding of labeled SJ-9A4 to NALM-1 and NB cells. Other MoAb: J5, PI 153/3 and monoclonal anti-HLA-DR antibodies gave no inhibition. A solid phase indirect radioimmunometric assay (IRA) was developed which enabled the detection of P24 from C-ALL cells, utilizing its ability to bind the Ricinus communis agglutinin (RCA1) or wheat germ agglutinin (WGA) and SJ-9A4 simultaneously. When BA-2 and DU-ALL-1 were used in place of SJ-9A4, similar IRA results were obtained. Using the RCA1/SJ-9A4-IRA, P24 from as few as 1.6 X 10(4) cells of a C-ALL cell line could be detected; however, similar extracts of NB cell lines were negative despite high levels of SJ-9A4 binding to intact cells. The presence of P24 in NB extracts was demonstrated by (1) preincubation of NB extracts with SJ-9A4 which blocked MoAb binding to P24 and (2) immunoadsorption of P24 from solubilized membranes of 35S-methionine (met) labeled NB cells. Treatment of NB cells with neuraminidase did not result in IRA binding when either RCA1 or WGA were used as the solid phase lectin indicating that the differences in lectin affinity are not due to over sialation of NB membrane glycoproteins. These findings demonstrate a difference in the glycosylation of P24 from C-ALL and NB cells.

A monoclonal antibody (SJ-9A4) to P24 present on common alls, neuroblastomas and platelets - II. Characterization of P24 and shedding in vitro and in vivo.

The release of soluble P24 antigen into culture medium by common acute lymphoblastic leukemia (C-ALL) and neuroblastoma (NB) cell lines was studied. P24 release by C-ALL cells was detected using a solid phase indirect radioimmunometric assay (IRA) which combines the specificity of lectins and monoclonal antibodies (MoAb) and using immunoadsorption of labeled P24 in spent medium from cells incubated with 35S-methionine (met). No P24 was present in the medium of cells pulse labeled at 37 degrees C when they were placed at 4 degrees C, thus this is an active process. P24 release by NB cells could not be detected by IRA, but could be detected by immunoadsorption of spent medium of metabolically-labeled cells. The absence of IRA activity of P24 from NB spent medium was due to decreased glycosylation and thus no binding to the lectins employed in the IRA was observed. This was confirmed by lectin affinity chromatography which showed that P24 in the spent medium from C-ALL cells bound Ricinus communis agglutinin (RCA1), wheat germ agglutinin (WGA), concanavalin A (Con A), and lentil lectin (LcH), but not peanut agglutinin (PNA). P24 from NB cell spent medium did not bind to any of these lectins. The lectin affinity of P24 derived from lymphoblasts is consistent with the presence of N-linked oligosaccharide chains having N-acetyl glucosamine residues, a mannose core, and a terminal D-galactose. P24 from C-ALL cell spent medium was present in the 35-45% fraction of a saturated ammonium sulfate (SAS) partition of spent medium. The P24 antigen was detected in the fractionated plasma of five patients with C-ALL at the time of diagnosis and was undetectable when the patients had achieved a complete remission. Plasma from 2 patients with P24 negative ALL, normal human plasma, and normal human serum had no detectable activity.

Aneuploidy and percentage of S-phase cells determined by flow cytometry correlate with cell phenotype in childhood acute leukemia.

Cellular DNA content distributions of propidium-iodide-stained bone marrow blasts were determined by flow cytometry (FCM) for 225 untreated children with acute leukemia and were correlated with leukemia cell phenotype and karyotype. Aneuploidy of the primary malignant stem line was detected in 54 cases (24%): 51 hyperdiploid and 3 hypodiploid. A second stem line with approximately twice the DNA content of the primary stem line was recognized by FCM in 28 cases (23 ALL, 5 ANLL) and may be an important source of leukemia cell heterogeneity. The degree of DNA content abnormality detected by FCM was highly correlated (r = 0.98) with the number of whole chromosome gains or losses in the leukemia karyotype. Aneuploidy detectable by FCM was more frequent in acute lymphoblastic leukemia (ALL) (52 of 173, 30.1%) than in acute nonlymphoblastic leukemia (2 of 52, 3.8%) (p less than 0.001). In the ALL group, aneuploidy was significantly correlated with the cell surface expression of common ALL antigen: 46 of 127 antigen-positive cases were aneuploid compared to 6 of 46 antigen-negative cases (p less than 0.003). Only 2 of 21 cases of T-cell ALL without common ALL antigen had detectable aneuploidy, which was significantly less than in the common ALL group (p = 0.02). The median percentage of cells in S-phase was significantly greater for B-cell and erythrocyte rosette-positive T-cell ALL, than for the other phenotypic subgroups. We conclude that aneuploidy and S-phase cell percentage are correlated with the state of leukemia cell differentiation. The biologic basis for the correlation is not established, but may be linked to the process of malignant transformation.

Prognostic importance of chromosome number in 136 untreated children with acute lymphoblastic leukemia.

Leukemia cell karyotypes were determined at diagnosis for 136 of 159 consecutive patients with acute lymphoblastic leukemia (ALL) who were followed for up to 35 mo. Ninety patients (67%) had abnormal karyotypes. Five chromosome categories were designated, based on the distribution of modal numbers: hyperdiploid greater than 50 (n = 41), hyperdiploid 47-50 (n = 18), pseudodiploid (n = 28), normal (n = 46), and hypodiploid (n = 3). Treatment response was assessed for the categories in terms of time to failure (induction failure, first relapse, or death). Children in the hyperdiploid greater than 50 category had the best responses to treatment, with only 2 failures, and those in the pseudodiploid category had the poorest (p less than 0.001). The remaining 3 chromosome categories had intermediate responses and formed a third prognostic group. This same influence of chromosome number on time to failure was evident within the 2 clinical prognostic groups: high risk, signified by a leukocyte count greater than 100 X 10(9)/liter, meningeal leukemia, mediastinal mass, or the presence of blasts that formed rosettes with sheep erythrocytes at 37 degrees C, and standard risk, indicated by the absence of these features. The influence of chromosome number on time to failure was also the same within the historically favorable prognostic group that had common ALL. Results of a multivariate analysis indicated that chromosome number was the strongest single predictor of outcome (p less than 0.001) and was the only variable that added significant prognostic information to leukocyte count (p less than 0.001). The combination of chromosome number and leukocyte count should more clearly distinguish patients with ALL at low or high risk of relapse.

Relationship of pretreatment lymphoblast proliferative activity and prognosis in 97 children with acute lymphoblastic leukemia.

We have analyzed the pretreatment 3H-thymidine labeling indices in blood and marrow blast cells from 97 children with acute lymphoblastic leukemia (ALL) and circulating blasts. The median marrow labeling index (LI) was 6.2% (range 0.8%--32.7%) and the median blood LI, 3.2% (range 0.3%--20%). Blood LI was significantly correlated with leukocyte count and rosette-forming (E+) lymphoblasts but not with central nervous system leukemia or thymic mass at diagnosis. Marrow LI was related to E+ blasts only. In children with E+ leukemia, both blood and marrow LIs were significantly higher than values for other ALL subtypes (p less than 0.01) excluding undifferentiated ALL, which was characterized by an increased blood LI. Eighteen patients had a blood LI that either equaled or exceeded the marrow LI; apart from age, the clinical features, blast phenotypes, and treatment responses of this group were similar to those of patients with blood LI less than marrow LI. Among 51 patients assessed for treatment response, the estimated median length of remission was significantly shorter for those with a blood LI greater than 4% (p = 0.002) or a marrow LI greater than 6% (p = 0.011). By Cox-regression analysis, the pretreatment proliferative activity of blood and marrow blasts, unlike other initial features studied, added significant prognostic information to leukocyte count in these patients with circulating blasts. The findings provide a cogent explanation for the differential clinical responsiveness of commonly recognized ALL subclasses.

Immunological definition of leukemic cell surface phenotypes.

Immunological phenotyping of blasts from over 200 children with acute lymphocytic leukemia (ALL) reveals both interpatient differences and phenotypic heterogeneity in the blast population from individual patients. A battery of five independent lymphocyte differentiation markers, erythrocyte-forming rosettes. T-cell antigens, Ia-like antigens, the common ALL antigen, and surface immunoglobulin, permit classification of all ALL specimens into four major marker groups. These are common, T-cell, B-cell, and undifferentiated ALL. Heterogeneity in the marker phenotypes within each of the major groups is observed. Within individual erythrocyte receptor-positive ALL specimens, phenotypic heterogeneity in the blast population is demonstrated. Sequential determinations of the blast phenotype during periods of active disease reveal a second example of intrapatient blast cell heterogeneity. Differences in phenotype of the dominant blast populations present prior to treatment and at relapse are observed in sequential studies of individual patients. These shifts in phenotype are nonrandom. They result most frequently from losses in single differentiation markers. A unifying hypothesis which explains these observations of phenotypic heterogeneity is that ALL blasts manifest limited lymphoid-like differentiation.