Long-term establishment of a human plasmacyte cell line derived from a patient with IgD multiple myeloma. I. Requirement of a plasmacyte-stimulating factor for the proliferation of myeloma cells in tissue culture

Cancer associated fibroblasts and tumor growth: focus on multiple myeloma

Cancer associated fibroblasts (CAFs) comprise a heterogeneous population that resides within the tumor microenvironment. They actively participate in tumor growth and metastasis by production of cytokines and chemokines, and the release of pro-inflammatory and pro-angiogenic factors, creating a more supportive microenvironment. The aim of the current review is to summarize the origin and characteristics of CAFs, and to describe the role of CAFs in tumor progression and metastasis. Furthermore, we focus on the presence of CAFs in hypoxic conditions in relation to multiple myeloma disease.

Malignant hematopoietic cell lines: in vitro models for the study of multiple myeloma and plasma cell leukemia

Multiple myeloma (MM) is a neoplasm of a terminally differentiated B-cell. The disease is progressive and always lethal characterized by the slow proliferation of malignant plasma cells in the bone marrow. Much of our current understanding of the biology of MM has been obtained by studying MM-derived cell lines. Human myeloma cell lines were shown to be suitable model systems for use in various fields of the biological sciences. However, it has proved very difficult to establish cell lines from plasma cell dyscrasias. Most reported MM cell lines have been derived from patients with advanced disease and from extramedullary sites. Nevertheless, within the last 20 years more than 100 cell lines have been established. A significant portion of this panel is partially or well characterized with regard to their cell culture, clinical, immunophenotypic, cytogenetic and functional features. Distinct immunoprofiles could be assigned to MM cell lines. All MM cell lines display chromosomal aberrations; in more than 80% of the cell lines analyzed, chromosome 14 band q32 (immunoglobulin heavy chain locus) is affected; the various types of 14q+ chromosomes showed different distributions among the MM cell lines. A large percentage of MM cell lines is constitutively interleukin-6-dependent or responsive to various cytokines. It is important to realize that not every cell line established from a patient with myeloma is a neoplastic cell line. So-called 'myeloma cell lines' have been previously reported and are still widely used which are in reality Epstein-Barr virus (EBV)-positive B-lymphoblastoid cell lines. The presence of the EBV-genome in residual normal B-cells provides them with a selective growth advantage after explantation. In summary, a significant number of authentic and well-characterized MM cell lines has been established and described. The availability of these bona fide MM cell lines is of great importance for the study of the biology, etiology and treatment of the disease.

Human bone marrow stroma-dependent cell line MOLP-5 derived from a patient in leukaemic phase of multiple myeloma

The novel multiple myeloma (MM) cell line MOLP-5 and its homologous sister cell line B407, a lymphoblastoid cell line (LCL), were established from the peripheral blood of a 71-year-old Japanese patient with Bence-Jones kappa-type multiple myeloma (stage IIIB with hyperammonaemia and hypercalcaemia). The growth of MOLP-5 cells is constitutively dependent on bone marrow stroma (BST) cells; none of the cytokines tested nor the culture supernatant of the bone marrow stroma cells could support the growth of MOLP-5. Wright-Giemsa-stained MOLP-5 cells showed typical plasma cell morphology with abundant cytoplasm and one to three nuclei. The immunoprofile of MOLP-5 corresponds to that seen typically in primary MM cells: positive for cytoplasmic immunoglobulin (Ig) kappa light chain, CD28, CD29, CD38, CD40, CD44, CD49d, CD54, CD56, CD58, CD71, CD138 and PCA-1; the cells were negative for surface Ig and various other B-cell, T-cell and myelomonocyte-associated immunomarkers. Interleukin 6 (IL-6) receptor mRNA was found in the reverse transcriptase polymerase chain reaction (RT-PCR) analysis. IL-6 and IL-10 could induce cellular proliferation in short-term induction experiments. IL-6 or IL-10 production was not detected by specific enzyme-linked immunoabsorbent assay (ELISA). MOLP-5 cells expressed parathyroid hormone-related protein (PTHrP) at the mRNA level. Cytogenetic analysis showed the typical t(11; 14) chromosome abnormality. The novel MOLP-5 cell line together with the B407 B-LCL sister line will be useful model systems in the investigation of the biology of MM.

Human lymphoblastoid cell line producing specific antibody against Rh-antigen D

A lymphoblastoid cell line producing specific anti-Rh antibody against D determinant was established by Epstein-Barr virus (EBV) infection. The lymphocytes were from an immunized male donor with high titre of anti-D antibody. The cells were preselected by rosetting them with Rh-positive erythrocytes before EBV infection. The cell line produced specific antibody of IgG class, namely IgG1 subclass, but it also produced nonspecific IgM and IgG. By rerosetting the cell line, the specific antibody-producing population could be enriched and the antibody titre increased in the culture supernatant to the level of immune sera.

In vitro culture of primary plasmacytomas requires stromal cell feeder layers

Attempts to grow primary murine plasmacytomas in vitro have, to date, been largely unsuccessful. In this study, we demonstrate that long-term in vitro growth of primary plasmacytomas is accomplished by using feeder layers composed of stromal cells from the initial site of plasmacytomagenesis. The early neoplastic lines established in this manner are dependent on physical contact with the stromal layer, which is mediated in part by CD44, for growth and survival. The stromal cells provide at least two stimuli for the plasma cells, one being interleukin 6 and the second, of unknown nature, resulting from direct physical interaction that cannot be replaced by soluble factors. These plasma cell lines have been passaged for as long as 20 months yet still maintain characteristics associated with primary plasmacytomas as they will grow in vivo only in pristane-primed animals, indicating a continued dependence on the pristane-induced microenvironment characteristic of early-stage tumors. The ability to grow primary plasmacytomas in culture and maintain their "primary" properties provides a model system for detailed analysis of early events in plasma cell tumor progression involving neoplastic cells completely dependent on physical contact with a stromal feeder layer for survival and expansion.

IgD myeloma presenting as a testicular tumor: establishment and characterization of an IgD-secreting myeloma cell line

A 72-year-old man presented with a left testicular tumor and underwent orchiectomy. The tumor was massively infiltrated with myeloma cells bearing monoclonal cytoplasmic IgD lambda. Three months after orchiectomy, he developed huge abdominal masses and subsequently ascites containing numerous myeloma cells. An IgD-secreting myeloma cell line, designated delta-47, was established from the ascites. This cell line expressed CD4 and CD38, but lacked Fc and complement receptors, surface immunoglobulin, CD19, HLA-DR, and PCA-1. CD30 was detected on the cultured cells but not on the ascites tumor cells. Delta-47 cells secreted the same immunoglobulin (IgD lambda) as was found in the patient's serum. The light chain had a molecular weight of 35 kD which was larger than that of the normal light chain. Chromosome analysis of delta-47 revealed an aneuploid karyotype with complex abnormalities including 1q+, 2p+, and 14q+. To our knowledge, this is the only IgD-secreting myeloma cell line and would provide a useful tool for the study of IgD production and IgD myeloma.

The establishment of an interleukin-6-dependent myeloma cell line (FLAM-76) carrying t(11;14)(q13;q32) chromosome abnormality from an aggressive nonsecretory plasma cell leukemia

A new myeloma cell line designated FLAM-76 was established from a patient with an aggressive nonsecretory plasma cell leukemia. The cell line exhibited morphologic features of flaming cells and contained an abundant eosinophilic cytoplasm with many dilated cisternae of rough endoplasmic reticulum. FLAM-76 cells were positive for cytoplasmic kappa (kapp)-type immunoglobulin but did not secrete it into the culture medium. The cells proliferated in the presence of exogenous interleukin-6 (IL-6) and more than 800 pg/ml of IL-6 was necessary for their continuous growth. The cells did not grow without IL-6, and they did not produce IL-6. Thus, the growth of FLAM-76 appeared to be regulated by the paracrine mechanism of IL-6. Alpha-interferon (alpha-IFN) inhibited the IL-6-dependent growth of FLAM-76 in doses greater than 1000 U/ml. FLAM-76 cells expressed CD38 (OKT10) and cell adhesion-associated antigens such as CD44 and CD54 (ICAM-1). Chromosome analysis revealed FLAM-76 to have a hypodiploid chromosome constitution with t(11;14)(q13;q32) abnormality, which frequently is seen in neoplasms of B-cell origin. Immunoglobulin (JH and Ck) gene rearrangement (but no BCL-1 gene rearrangement) was found in this cell line.

Characterization of a human plasmacytoma line

The TH line was established by bringing tumour cells from a multiple myeloma patient into suspension culture and subsequently cloning them by limiting dilution. The cultured cells show marked heterogeneity; there are ultrastructural differences between small and large TH cells, particularly with respect to the rough endoplasmatic reticulum (RER). Karyotyping revealed chromosome numbers in the triploid range, with many structural abnormalities, at the 14q32 region among others. A t(14;18) could not be demonstrated. TH was shown to have germline and a rearranged allele for kappa light chain, and only a single rearranged gene for heavy chain immunoglobulin. TH expressed PCA-1, CD9, CD28 and CD38 antigens, HLA class II, RER and kappa light chain, but few or no other antigens associated with the B-cell lineage. Light chain kappa and trace amounts of IgG3 were found intracellularly as well as in culture supernatant. The addition of IL-6 to cultures of TH increased proliferation, as well as the secretion of kappa light chain and the membrane expression of CD28 and CD38 antigens. Because TH has relatively few B cell markers on its membrane, it may be useful for the induction of monoclonal antibodies specific for human plasma cells. It also provides a model for the demonstration that IL-6 can act as a paracrine growth and differentiation factor for cells of myelomal origin.

Limiting dilution cloning of B cells from patients with multiple myeloma: emergence of non-malignant B-cell lines

Multiple myeloma (MM) is a B-cell malignancy characterized by the accumulation of slowly proliferating malignant plasma cells in the bone marrow (BM). Several reports have shown the existence of an abnormal B-cell compartment including proliferative idiotypic B cells (i.e., B cells bearing the same idiotypic determinants as the myeloma protein) in the BM and peripheral blood (PB) of patients with MM. In order to study whether this abnormal compartment can be grown in vitro, we cultured the PB and BM of 23 patients with MM using limiting dilution methods. Our purpose was to restrict the effect of suppressor cells and the possible overgrowth of the cultures by the more rapidly growing B cells, which occurs in bulk cultures. Spontaneously growing cells were obtained only from patients seropositive for the Epstein-Barr virus (EBV) and all the cultures were composed of B cells carrying the EBV genome. Thus, positive cultures were generated only in the presence of B cells latently infected with EBV in vivo. The mean frequency of these B cells (1 in 25,000 B cells) was as low in MM patients as in healthy donors. This low frequency indicated that malignant cells do not bear the EBV genome in vivo and that the in vivo regulation of the EBV infection is unaffected in patients with MM. No Ig-gene rearrangements, specific of the autologous myeloma cells, were found in the cell lines obtained from BM or PB. Thus, the putative malignant B cells or myeloma cells were not able to generate cell lines in vitro, either spontaneously or after endogenous infection with EBV.

Establishment of two interleukin 6 (B cell stimulatory factor 2/interferon beta 2)-dependent human bone marrow-derived myeloma cell lines

Two IL-6-dependent human multiple myeloma cell lines, ILKM2 and ILKM3, were established from the bone marrow of patients with IgG-K multiple myeloma. Both cell lines had the typical morphology and immunocytochemical features of myeloma cells. The surface phenotype of both cell lines was PCA-1+, OKT10+, CD10(J-5)-, CD19(B4)-, CD20(B1)-, CD21(B2)-, and OKIa-1-. A monoclonal cytoplasmic Ig, IgG-K or K L chain, was positive in ILKM2 or ILKM3, respectively. EBV nuclear antigen was negative in both cell lines. They proliferated in the presence of macrophages or macrophage-derived factors (MDF). Among the recombinant cytokines examined, IL-6 most strongly augmented the growth of both cell lines. The anti-IL-6 antibody completely inhibited the IL-6-dependent growth and almost completely inhibited the MDF- or purified MDF-dependent growth of both cell lines, ILKM2 and ILKM3 are now being maintained in the culture medium containing 2 ng/ml rIL-6. These results suggest that IL-6 produced by macrophages may play an important role in the growth of myeloma cells in vivo and that macrophages or IL-6 can be used for establishing human myeloma cell lines.

Two new IgA1-kappa plasma cell leukaemia cell lines (JJN-1 & JJN-2) which proliferate in response to B cell stimulatory factor 2

Two new cell lines with the phenotype of terminally differentiated B cells have been derived from the presentation bone marrow of a patient with plasma cell leukaemia. They express the same immunoglobulin (A1-kappa) as the original bone marrow cells. JJN-1 is an hypodiploid, slow-growing line with a plasmacytic morphology, which grows in medium with 15-20% fetal calf serum. When JJN-1 was stimulated with a supernatant ('ESG') containing B cell stimulatory factor 2 (BSF-2/IL-6), a hypotetraploid sub-line, JJN-2, was selectively stimulated. JJN-2 is dependent on ESG for survival. The stimulatory effect of ESG can be completely abrogated by an anti-BSF-2 monoclonal antibody. However, purified BSF-2 alone only produces sub-maximal stimulation of the lines. Both lines show complex karyotypic abnormalities, including 14q- and del(6q). JJN-1 and JJN-2 may be useful for the study of late B cell differentiation and for use as immunogens for the generation of anti-plasma cell monoclonal antibodies.

Establishment and characterization of a permanent human IgA2/kappa myeloma cell line

A human myeloma cell line designated LOPRA-1 has been established from ascites fluid containing malignant plasma cells of a patient with IgA2/kappa multiple myeloma. The cultured cells which are Epstein-Barr virus (EBV) negative have retained the morphological, cytochemical, ultrastructural and immunophenotypical features of well-differentiated plasma cells. They express the plasma cell antigen PCA-1, the antigens CD28 (Kolt-2) and CD38 (OKT10), the transferrin-receptor (OKT9), and some epitopes of the CD24 antigen (HB8, VIB E3), but are negative for surface immunoglobulins. HLA class II antigens (HLA-DP, -DQ, -DR) and other B-cell markers such as CD10 (CALLA), CD19 (B4), CD20 (B1), CD21 (B2), CD22 (HD39), CD23 (MHM6), CD37 (BL14) and CD39 (G28-8) as analysed by both flow cytometry and immunocytochemistry (PAP/APAAP). With respect to immunoglobulin synthesis, two stable clones were selected by single cell cloning: clone LOPRA-1/5 synthesizes large amounts of alpha 2 heavy and kappa light chains, but secretes only small amounts of these molecules, whereas clone LOPRA-1/4 is clearly devoid of intracellular immunoglobulin heavy and light chains and thus appears to be a chain loss variant. Cytogenetic analysis revealed a pseudotriploid phenotype with several structurally abnormal marker chromosomes: 3n + -, 70, XX, -X, -1, -4, -6, -8, -8, -13, -16, +7, +18, +21, +i(1q), +i(1q), +6q-, +3mar.

Establishment and characterization of a human IgA-kappa-secreting plasma cell line (MT3)

We have established a new human plasma cell line from the peripheral blood of a patient with an IgA-kappa plasma-cell leukemia. Morphological, immunological, cytogenetic and molecular studies confirm that the cultured cells are derived from the same clone of leukemic plasma cell in vivo. The established cell line (MT3) grows in suspension, secretes high amounts of IgA kappa and exhibits morphological and ultrastructural characteristics of plasma cells. Surface marker analysis shows that both primary and cultured cells express the plasma-cell-associated antigens PCA-1 and T10, while specific B- and T-cell determinants and EBV nuclear antigen are undetectable. In the established cell line a few cells express Ia-like and CALLA antigens. Cytogenetic analysis of MT3 cells reveals a prevalent hypertriploid karyotype with constant chromosomal aberrations consisting of 14q+, 22q- and marker chromosomes.

Two distinct human myeloma cell lines originating from one patient with myeloma

Two distinct cell lines (OPM-1 and OPM-2) were established from the peripheral blood of a 56-year-old female myeloma patient at the stage of terminal leukemic evolution associated with loss of cytoplasmic immunoglobulin heavy chain (G lambda----lambda). The lines grew in suspension with a doubling time of 36-42 hr and 30-36 hr, respectively. EBNA was absent from both lines. The lines synthesized cytoplasmic lambda-chain, but had no detectable surface immunoglobulins. Fc receptors and complement receptors could not be detected in either line. The lines had very complex chromosomal abnormalities, but the patterns of chromosomes differed greatly between the two lines. The two lines, together with the RPMI 8226 line established by Matsuoka et al. (1967), were analyzed for phenotypic expression as defined by a panel of monoclonal antibodies to B cells (B1, BA-1, BA-2, BA-3, OKIa-1 and OKT10/BMA0100). Neither OPM-1 nor OPM-2 reacted with any of the antibodies tested except OKT10. OPM-1 cells reacted weakly (less than 30%) with OKT10/BMA0100, while OPM-2 cells showed a fluctuating reactivity, ranging from 40 to 80%, with OKT10/BMA0100. In contrast, RPMI 8226 reacted strongly with OKT10 and BA-2. These results demonstrate the presence of phenotypic heterogeneity in all 3 myeloma cell lines, suggesting that the lines might represent different stages of terminal B-cell development.

Human monoclonal antibodies: methods of production and some aspects of their application in oncology

The currently available methods for the production of human monoclonal antibodies (Mabs) are: mouse-human hybrids, human-human hybrids, EBV transformation, and fusion of EBV-transformed specific B-lymphocytes with a malignant cell line. Each method has its advantages and drawbacks, but they are all inferior to an optimal functioning mouse hybridoma system. A significant obstacle is the lack of a reproducible method to obtain high amounts of antigen-specific B-lymphocytes. However, it seems that newly developed in vitro antigen-priming methods may be a significant aid to the solution of this problem. Human Mabs have already been obtained against some types of human cancer, and the reactivity pattern has provided some biological information that seems not to be obtainable with non-human Mabs. It furthermore seems that the technology for production of human Mabs now has progressed to the stage where it permits a realistic hope that they soon can be applied in the diagnosis and treatment of human cancer.

ARH-77, an established human IgG-producing myeloma cell line. I. Morphology, B-cell phenotypic marker profile, and expression of Epstein-Barr virus

Monolayer cultures of ARH-77 cells, a human myeloma cell line propagated in vitro, display a variety of morphologic entities ranging from small lymphocytes to classic plasma cells. The cells show intense pyronin and periodic acid-Schiff affinity but are negative for colloidal iron, sudan black, and naphtol AS-D chloroacetate esterase. The cells exhibit phenotypic markers pertaining to each stage of the B-cell lineage. They fail to display sheep erythrocyte and bovine erythrocyte-IgG antibody complex rosettes, common acute lymphocytic leukemia (ALL) antigens and T-cell antigens, but most cells display surface complement receptors, Ia-like antigens, and surface and intracytoplasmic Ig. Monoclonal antibodies were negative for T-antigens, myelomonocytic cell antigens, leukemia-associated antigens, and BA-1 and OKT-10 antigens. However, 100% of the cells were positive with OKT-9 and B3/25 antibodies that are specific for transferrin receptors. About 50% to 80% of the cells were positive for surface membrane immunoglobulin (kappa IgG) and about 10% to 50% for cytoplasmic immunoglobulin (kappa IgG). Virtually all cells were positive when tested for nuclear Epstein-Barr virus antigens.

Human monoclonal antibodies

The technology for the production of murine monoclonal antibodies has been refined enormously since its introduction in 1975. However, the technology for generating human monoclonal antibodies has only recently come into its own. In this review, three currently available approaches to the production of human monoclonal antibodies are described. These include the hybridoma technique, based on the fusion of antibody-producing human B lymphocytes with either mouse or human myeloma or lymphoblastoid cells; the EBV immortalization technique, based on the use of Epstein-Barr virus (EBV) to 'immortalize' antigen-specific human B lymphocytes; and the EBV-hybridoma technique, based on a combination of the first two methods. The EBV-hybridoma system retains the advantageous features of the other two systems while overcoming their pitfalls and may be the current method of choice for producing human monoclonal antibodies with a defined specificity.

The human tumor cloning assay in cancer drug development. A review

Animal studies with transplantable tumor cell lines suggested that the sensitivities of the in vitro tumor cultures to certain anticancer drugs agreed with the drug sensitivities of the same tumors in vivo. Soft agar cloning techniques have been established for human myeloma and ovarian cancer cells. Refinement of the techniques now permits cloning of most human malignancies. Drug sensitivity studies have been conducted measuring the reduction in the number of tumor colonies formed. Clinical trials showed that approximately one half of patients whose cells demonstrate in vitro sensitivity to a drug will obtain a clinical response to the same drug. Patients whose cells appear resistant to a certain drug in vitro rarely respond to the drug clinically. In vitro drug sensitivity testing may eventually allow some individualization of chemotherapy. In addition it already appears that these techniques may be excellent for screening new drugs with specific anticancer potentials.

A human plasma cell line: induction and characterization

A stable line of IgG K producing human plasma cells was established from a myelomatous human bone marrow using conditioned media from a rapidly metabolizing lymphoblast line, RPMI 4098. Growth in RPMI 1640 (15% fetal calf serum) at 6% CO2 promoted a 62-hour doubling time with a preferred cell concentration of 1 x 10(6)/mL. Surface marker studies showed: no receptors for sheep erythrocytes, no surface immunoglobulins, variable number of cells bearing complement receptors and 83% bearing Fc receptors. Although transmission electron micrographs demonstrated a poorly developed endoplasmic reticulum, radioimmunoassay showed 23 ng IgG and 28.7 ng Kappa were produced by 1 x 10(6) cells in 72 hours. Further, the cells are lipase, esterase and Epstein-Barr nuclear antigen negative. ASG banding showed a total chromosome number that varied from 46--49. Since the number of human plasma cell lines is limited, it is felt that this line will augment the immunobiological study of human myeloma.

Establishment and characterization of a human myeloma cell line (KMM-1)

A new cell line (KMM-1) was established from a subcutaneous plasmacytoma of a 62-year-old male with multiple myeloma. Immunological studies indicated that cultured cells were derived from the same clone of myeloma cells in vivo: smeared cells were stained with fluorescein-conjugated globulin of antisera monospecific to lambda-chain, and lambda-chains in the cell extracts and in culture media were identical to the Bence-Jones protein found in the patient's urine. The cell line grew in suspension with prominent nucleoli and rough endoplasmic reticulum. Cells had the karyotype of 47, X, -Y, Iq+, -2, +t(1:2) (cen:cen), +7, 12q+, 14q+, +mar and carried no Epstein-Barr virus-determined nuclear antigen. Surface markers were as follows; E rosette (-), IgG Fc receptor (-), C3 receptor (-), S-Ig (+), TdT (-), asialo-GM1 (-). The reasons for the successful establishment of the myeloma cell line are discussed.

Separation of normal mature bone marrow plasma cells

A three-phase purification process for the separation of normal bone marrow plasma cells is described. Material was obtained from haematologically normal humans and baboons. Known monoclonal and polyclonal B cell activators were avoided both in vivo and in vitro. In Phase I, bone marrow fragments were separated from cell suspensions by buoyant density methods. Marrow fragments were shown to be richer in plasma cells than the corresponding marrow cell suspensions. Phase II consisted of culturing fragments by a simple suspension method in which a selective affinity of plasma cells and marrow stromal cells resulted in further concentration of plasma cells with discharge of haemopoietic elements. Maximum concentration of plasma cells occurred within 7 d. In phase III, fragments were disaggregated with trypsin, and the marrow stromal cells were removed by their adherence properties. The resulting non-adherent fraction comprised approximately 85% plasma cells. The process allows for direct quantitative evaluation of normal plasma cell physiology in vitro.

Myelomatous pleural effusion: clinical course and immunologic characterization of the pleural fluid cells

Multiple myeloma is a disease that infrequently involves nonreticuloendothelial tissues and rarely causes pleural effusion. A 59-year-old woman had pleural effusion as the major manifestation of multiple myeloma. Light microscopy of her pleural fluid with Wright stained preparations showed all cells to be bizarre and often multinucleated plasmacytes. Electron microscopy confirmed these results. Intracellular immunofluorescence revealed IgG-kappa immunoglobulin (Ig) in greater than 90% of these cells. Surface immunofluorescence using anti-Ig sera was seen on less than 5% of the pleural fluid cells. 3H leucine incorporation into Ig in vitro was measured for these cells, and secretory curves were obtained that have the typical secretory kinetics of bone marrow plasmacytes. This demonstrates that such cells are viable and are able to synthesize and release immunoglobulin. Treatment of our patient with prednisone, melphalan, and cyclophosphamide resulted in symptomatic improvement and complete resolution of her pleural effusion. Pleural effusion is an unusual but important complication of multiple myeloma and does not necessarily carry the grave prognosis implied in previous reports.

Production of antibody to tetanus toxoid by continuous human lymphoblastoid cell lines

Peripheral lymphocytes from human volunteers boosted with tetanus toxoid were cultured after in vitro infection with Epstein-Barr virus. Forty-four continuous lymphoblastoid lines were established which continued to secrete human gamma globulin; seven of these secreted antibody to tetanus toxoid. Subcultures derived from limiting dilution experiments continued to secrete the antibody. Some of these antibody-secreting cells have been in continuous culture for more than 6 months.

Human leukemic "null" cell line (NALL-1)

A human lymphoblast cell line, NALL-1, was established from the peripheral blood of a patient with acute lymphoblastic leukemia (ALL). NALL-1 cells had neither properties of T and B cells nor Epstein-Barr virus (EBV). Many characteristics of the NALL-1 line were distinct from those of numerous EBV-positive lymphoblastoid cell lines previously reported. NALL-1 cells are considered to have originated from the donor's leukemic cells on the basis of their cytogenetic, morphologic and functional features. The NALL-1 line is the first human leukemic "null" cell line derived from ALL. The significance of this cell line is disscussed.

Primary bioassay of human myeloma stem cells

The ability to clone primary tumors in soft agar has proven useful in the study of the kinetics and biological properties of tumor stem cells. We report the development of an in vitro assay which permits formation of colonies of human monoclonal plasma cells in soft agar. Colony growth has been observed from bone marrow aspirates from 75% of the 70 patients with multiple myeloma or related monoclonal disorders studied. Growth was induced with either 0.02 ml of human type O erythrocytes or 0.25 ml of medium conditioned by the adherent spleen cells of mineral oil-primed BALB/c mice. 5-500 colonies appeared after 2-3 wk in culture yielding a plating efficiency of 0.001-0.1%. The number of myeloma colonies was proportional to the number of cells plated between concentrations of 10(5)-10(6) and back-extrapolated through zero, suggesting that colonies were clones derived from single myeloma stem cells. Morphological, histochemical, and functional criteria showed the colonies to consist of immature plasmablasts and mature plasma cells. 60-80% of cells picked from colonies contained intracytoplasmic monoclonal immunoglobulin. Colony growth was most easily achieved from the bone marrow cells of untreated patients or those in relapse. Only 50% of bone marrow samples from patients in remission were successfully cultured. Tritiated thymidine suicide studies provided evidence that for most myeloma patients, a very high proportion of myeloma colony-forming cells was actively in transit through the cell cycle. Velocity sedimentation at 1 g showed myeloma stem cells sedimented in a broad band with a peak at 13 mm/h. Antibody to granulocyte colony-stimulating factor did not reduce the number or size of the colonies. Increased numbers of myeloma colonies were seen when the marrow was depleted of colony-stimulating factor elaborating adherent cells before plating. This bioassay should prove useful in studying the in vitro biological behavior of certain bone marrow-derived (B)-cell neoplasia. In addition, systematic and predictive studies of anticancer drug effects on myeloma stem cells should now be feasible.

Severe combined immunodeficiency with B lymphocytes: in vitro correction of defective immunoglobulin production by addition of normal T lymphocytes

A 6 1/2-month-old male with severe combined immunodeficiency (SCID) had a low percentage and number of T cells (11%; 241/mm3) and a high percentage and number of B cells (52%; 1187/mm3) and null cells (37%; 868/mm3). In vitro studies were performed to determine if this child's primary defect involved differentiation of both T and B lymphocytes or if failure of B lymphocytes to differentiate into immunoglobulin producing cells was secondary to T lymphocyte abnormalities. Immunoglobulin production by lymphocytes in response to polyclonal mitogens (pokeweed mitogen and foetal calf serum) was measured by pulse-labelling cells with 3H-leucine and then precipitating cytoplasmic and secreted immunoglobulins with polyvalent anti-human immunoglobulin and S. aureus (Cowan strain I) protein A. The patient's lymphocytes did not synthesize immunoglobulins in vitro in response to mitogens. They did not suppress synthesis of immunoglobulins by normal lymphocytes. However, addition of normal purified T cells, which themselves did not synthesize immunoglobulins, enabled the patient's B lymphocytes to become immunoglobulin synthesizing and secreting cells. Gamma, mu, and light chains were secreted. This suggests that the primary abnormality was in the T-cell axis at the level of lymphoid stem cells or prothymocytes and that failure of B lymphocytes to become immunoglobulin-producing cells was secondary to this defect.