Clonal differences in response to T cell replacing factor (TRF) for IgM secretion and TRF receptors in a human B lymphoblast cell line

Bioinspired Hierarchical Carbon Structures as Potential Scaffolds for Wound Healing and Tissue Regeneration Applications

Engineered bio-scaffolds for wound healing provide an attractive treatment option for tissue engineering and traumatic skin injuries since they can reduce dependence on donors and promote faster repair through strategic surface engineering. Current scaffolds present limitations in handling, preparation, shelf life, and sterilization options. In this study, bio-inspired hierarchical all-carbon structures comprising carbon nanotube (CNT) carpets covalently bonded to flexible carbon fabric have been investigated as a platform for cell growth and future tissue regeneration applications. CNTs are known to provide guidance for cell growth, but loose CNTs are susceptible to intracellular uptake and are suspected to cause in vitro and in vivo cytotoxicity. This risk is suppressed in these materials due to the covalent attachment of CNTs on a larger fabric, and the synergistic benefits of nanoscale and micro-macro scale architectures, as seen in natural biological materials, can be obtained. The structural durability, biocompatibility, tunable surface architecture, and ultra-high specific surface area of these materials make them attractive candidates for wound healing. In this study, investigations of cytotoxicity, skin cell proliferation, and cell migration were performed, and results indicate promise in both biocompatibility and directed cell growth. Moreover, these scaffolds provided cytoprotection against environmental stressors such as Ultraviolet B (UVB) rays. It was seen that cell growth could also be tailored through the control of CNT carpet height and surface wettability. These results support future promise in the design of hierarchical carbon scaffolds for strategic wound healing and tissue regeneration applications.

The Tumor Suppressor Protein TRAF3 Modulates GSK3 Activity and Susceptibility of B Lymphoma Cells to GSK3 Inhibition

TNF receptor-associated factor 3 (TRAF3) is an adapter protein that inhibits many signals that promote B cell survival and activation. Mice with a B cell-specific TRAF3 deficiency and humans with a rare haploinsufficiency in TRAF3 have enhanced development of BCLs as they age. Loss-of-function mutations in TRAF3 are common in B cell malignancies. Recent studies show that pharmacological inhibition of the enzyme glycogen synthase kinase 3 (GSK3), which regulates cellular growth, survival, and metabolism, inhibits growth and survival of BCL-derived B cells. In this study, we found that TRAF3 and GSK3 associated in B cells. The relative levels of TRAF3 in BCL cell lines correlated positively with the ratio of inactive to total GSK3β, and negatively correlated with susceptibility to GSK3 inhibition by the GSK3 inhibitory drug 9-ING-41, currently in clinical trials. Uniquely in BCLs with low TRAF3, GSK3 inhibition caused increased loss of the TRAF3-regulated, anti-apoptotic protein Mcl-1. GSK3 inhibition also blocked hyperresponsiveness to IL-6 receptor signaling in TRAF3-deficient BCL cells. Together, these results support the utility of 9-ING-41 as a treatment for BCL, and suggest that a decrease or loss of TRAF3 in BCLs could act as a biomarker for increased susceptibility to GSK3 inhibitor treatment.

The snRNP-associated U1A levels change following IL-6 stimulation of human B-cells

The U1A protein can be found both in a small-ribonucleoprotein particle (snRNP) that contains U1 RNA, or in a distinctive fraction, free of the snRNP, the SF-A complex. Both components have been shown to influence post- or co-transcriptional RNA processing reactions in HeLa cells. Since U1A may influence the processing of the immunoglobulin heavy chain pre-mRNA in B-cells, we wanted to see if the levels of U1A in either of its two forms changed following IL-6 stimulation to IgM secretion. Using antibodies that specifically recognize the two forms of U1A, snRNP-associated and snRNP-free, we found that approximately 16% of U1A is in the SF-A form in B-cells. We measured the levels of U1A protein in its two states in human B-cell lines both by flow cytometry and exhaustive immunoprecipitations. We found a significant decrease in the amount of snRNP-associated U1A following cytokine stimulation that correlates with the change-over to the secretory-specific poly(A) site use in the SKW 6.4 cell line. Meanwhile, the number of U1A molecules in the SF-A fraction of the pool remains nearly constant following induction to secretion. Our results suggest that the changing level of U1A in the snRNP fraction may be important for influencing Ig heavy chain mRNA processing.

Increase in the 64-kDa subunit of the polyadenylation/cleavage stimulatory factor during the G0 to S phase transition

The amount of the 64-kDa subunit of polyadenylation/cleavage stimulatory factor (CstF-64) increases 5-fold during the G0 to S phase transition and concomitant proliferation induced by serum in 3T6 fibroblasts. Higher levels of CstF-64 result in an increase in CstF trimer. The rise in CstF-64 occurs at a time when the amount of poly(A)-containing RNA rose at least 5-8 fold in the cytoplasm. Primary human splenic B cells, resting in G0, show a similar 5-fold increase in CstF-64 when cultured under conditions inducing proliferation (CD40 ligand exposure). Therefore, the increase in CstF-64 is associated with the G0 to S phase transition. As B cell development progresses, RNA processing changes occur at the Ig heavy chain locus resulting in a switch from the membrane- to the upstream secretory-specific poly(A) site. Treating resting B cells with agents triggering this switch in Ig mRNA production along with proliferation (CD40 ligand plus lymphokines or Staphylococcus aureus protein A) induces no further increase in CstF-64 above that seen for proliferation alone. The rise in CstF-64 is therefore insufficient to induce secretion. After stimulation of a continuously growing B cell line with lymphokines, a switch to Ig micrometer secretory mRNA and protein occurs but without a change in the CstF-64 level. Therefore, an increase in CstF-64 levels is not necessary to mediate the differentiation-induced switch to secreted forms of Ig-micrometer heavy chain. Because augmentation of CstF-64 levels is neither necessary nor sufficient for Ig secretory mRNA production, we conclude that other lymphokine-induced factors play a role.

SKW 6.4 cell differentiation induced by interleukin 6 is stimulated by butyrate

We investigated if sodium butyrate (NaBu), an inhibitor of histone deacetylase, and its analogs modulate cytokine-induced differentiation of the human B cell line SKW 6.4 transformed by the Epstein-Barr virus. NaBu markedly enhanced interleukin (IL)-6-induced IgM production with an accompanying increase in the level of histone H4 acetylation and augmented IgM production induced by IL-4 and phorbol 12-myristate 13-acetate. From both the enhancing effect of cell differentiation and the effect of inducing histone hyperacetylation in SKW 6.4 cells, other histone deacetylase inhibitors and NaBu analogs were divided into three groups: those that increased both IL-6-induced antibody production and histone acetylation, those that caused histone hyperacetylation, but failed to induce the differentiation, and those that were ineffective at inducing either activity. No agent that enhanced IgM production without inducing histone hyperacetylation was found among the inhibitors and analogs we tested. These results suggest that the increase in the histone acetylation is necessary, but it is insufficient to augment differentiation of SKW 6.4 cells. Thus another activity of NaBu in addition to the inhibition of histone deacetylase may be involved in promoting IL-6-induced differentiation. Our results also suggest that fatty acids that have a straight chain of four carbon atoms or are branched with four and five carbon atoms, which contain no hydrophilic substituents, or those with similar structures, show this other activity.

High-level expression of a biologically active human interleukin-6 mutein

We have constructed two different muteins of interleukin-6 (IL-6) which were expressed in Escherichia coli. Both muteins lack the first 22 N-terminal amino acids of native IL-6 and lack one or the other of the two naturally occurring pairs of cysteines at either position 45 and 51 or position 74 and 84 of IL-6. We found that there was a dramatic increase in the level of IL-6 produced from each mutein clone, compared to the level produced by the wild-type IL-6 clone. We also observed that the yield of soluble and properly refolded mutein IL-6 was highest when the cysteines at position 74 and 84 were left intact. The mutein IL-6 with cysteines at position 74 and 84 was as active as wild-type IL-6 and a lower concentration of the mutein IL-6 was required to reach maximal activity, compared to wild-type IL-6. The mutein IL-6 with cysteines at position 45 and 51 had a much reduced biological activity.

Construction and characterization of adenovirus co-expressing hepatitis B virus surface antigen and interleukin-6

Coexpression of biologically active interleukin 6 (IL-6), an immunoregulator, and hepatitis B virus surface antigen (HBsAg), an immunogen, was obtained using an adenovirus type 7 (Ad7) vector. Two recombinant adenoviruses (re-Ad) containing both the HBsAg and IL6 genes were constructed: one virus was capable of expressing IL6 with its signal peptide (spIL6) (Ad7::spIL6::HBsAg), and the second virus lacked this sequence (Ad7::IL6::HBsAg). A third recombinant contained only HBsAg (Ad7::HBsAg). All three Ad constructs were plaque purified and characterized in the A549 human lung cell line. The growth kinetics of the recombinants were similar to wild-type (wt) Ad7. The production and secretion of HBsAg (p24 and gp27) from cells infected with each re-Ad were at a level greater than 9 micrograms/10(6) cells by 118 h postinfection. Two IL-6 of approx. 24 and 27 kDa were produced and secreted into the culture medium from cells infected with Ad7::spIL6::HBsAg, and maximal accumulation occurred by 92 h p.i. at a level > 260 ng/10(6) cells. One cell-associated IL-6 of approx. 23 kDa was produced from cells infected with Ad7::IL6::HBsAg at a level > 12 ng/10(6) cells. Importantly, the Ad-produced IL-6 were determined to be biologically active by enhancing immunoglobulin production in lymphoblastoid cells. The co-production of IL-6 with HBsAg did not affect growth of these recombinant Ad, immunoreactivity of HBsAg, or the biological activity of IL-6 in tissue culture cells.

Efficient retroviral-mediated gene transfer into human B lymphoblastoid cells expressing mouse ecotropic viral receptor

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Subtractive antibody to a human immunosuppressive lymphokine affinity isolates a suppressive factor and blocks its function

Hybridoma suppressor factor(s) (HSF), secreted by a human thymus hybridoma (8E-24) established in this laboratory, suppresses Ig as well as IL-2 synthesis by peripheral blood mononuclear cells (PBMC). To aid in the characterization of this lymphokine, we prepared a subtractive antibody to HSF using the products of the hybridoma parent cell line to generate antibodies to irrelevant proteins. The concentrated supernatant fluid of the hybridoma parent cell line (CEM) was used to generate rabbit antibodies and titers of anti-CEM were monitored by enzyme immunoassay (EIA). Next, to remove factors shared by both the parent cell line and hybridoma, the concentrated supernatant fluid of 8E-24 (crude HSF) was passed over an immunoaffinity column, composed of protein A beads coupled to anti-CEM. The 'subtracted' HSF, termed partially purified HSF, was shown to be suppressive in vitro and was then used to prepare a second rabbit antisera. Using partially purified HSF as antigen, the presence of specific antibody was monitored by EIA. This antibody (anti-HSF) was used to prepare another immunoaffinity column by covalently coupling this antibody to protein A beads. Factors bound and then eluted from this affinity column were shown to inhibit IL-2 production by PBMC in a manner similar to HSF. Specific activity of the affinity purified HSF was 50 times that of partially purified HSF. Furthermore, the suppressive activity of affinity purified HSF was abrogated in the presence of anti-HSF. Western blot analysis performed on the concentrated crude HSF, using both the anti-HSF and anti-CEM antibodies, revealed the presence of several bands that selectively reacted with anti-HSF and not anti-CEM. Each of these bands were present in the affinity purified HSF. Of particular interest due to their similar size to the suppressive agent are a band at 12 kDa that reacts selectively with anti-HSF and is detected in crude and affinity purified HSF and a band at 10 kDa. In summary, this protocol resulted in the detection and separation of hybridoma specific proteins within the predicted size range of the suppressive lymphokine.

Host cell reactivation of cisplatin-damaged plasmid DNA in human non-T leukocyte cell lines

Host-cell reactivation of cisplatin-damaged pRSVcat was assessed in three B cell lines (SKW 6.4, WIL2-NS, RPMI 1788), the monocytic cell line THP-1, and promyelocytic HL-60 cells. IC50 values following a 3-day exposure of the five leukocyte cell lines to cisplatin ranged from 0.45 to 1.92 microM. Transfer of pRSVcat into all cell lines was effected by electroporation and the resultant CAT activity was measured 24 h later by a rapid single vial CAT assay. CAT activity corresponding to an average of 0.06 units of purified CAT enzyme was expressed by WIL2-NS cells. Very low to no expression of the CAT vector was observed in all other cell lines studied, despite the presence of intracellular levels of 3H-labelled pRSVcat comparable to WIL2-NS. Epstein-Barr virus transformed B cells (SKW 6.4 and RPMI 1788) did not successfully perform host cell reactivation. In WIL2-NS cells, platination of pRSVcat to defined levels of 5-40 platinum molecules per plasmid led to a graded reduction in CAT activity expressed following transfection. Platination levels of 20 and 40 platinum molecules per plasmid did not alter the efficiency of transfer of pRSVcat into these cells by electroporation. Data obtained in this study suggests that EBV transformation may possibly be a negative influence on host cell-reactivation assays for cisplatin-DNA damaged plasmid in non-T human leukocytes.

Effects of sex steroids on immunoglobulin M production by Epstein-Barr virus-transformed B-cell line SKW6-CL4

The effects of estradiol (E2), progesterone (P), and testosterone (T) on the production of immunoglobulin (Ig) M by Epstein-Barr virus-transformed B-cell line, SKW6-CL4, were investigated. Interleukin 6 (IL-6) induced IgM production by SKW6-CL4 cells in a dose-dependent manner without any significant increase in thymidine incorporation. E2 at concentrations ranging from 10(-10) to 10(-9) M enhanced IL-6-induced IgM production by SKW6-CL4 cells, whereas E2 at a high concentration of 10(-7) M inhibited both the IgM production and the growth of SKW6-CL4 cells. Time-course studies revealed that E2 acts in the early phase of differentiation of SKW6-CL4 cells in response to IL-6. On the other hand, P and T at physiological and superphysiological levels did not influence either the IgM production or the proliferation of SKW6-CL4 cells. These findings suggest a direct immunoregulatory effect of E2 on human B lineage cells and support the concept that E2 may have a role in the pathogenesis of some autoimmune diseases.

Expression of the fibronectin receptor VLA-5 is regulated during human B cell differentiation and activation

We examined the expression of VLA-5, a fibronectin receptor, during human B cell development and activation. VLA-5 is a member of the integrin supergene family; VLAs are heterodimers of at least six unique alpha chains sharing a common beta chain; most are involved in cell attachment to extracellular matrix (ECM). A hypothesis of haematopoietic development is that maturing cells leave the bone marrow because of the loss of VLA-5 during differentiation. However, mature B cells are not primarily circulating cells, and the role of ECM receptors in homing to peripheral lymphoid tissue and inflammatory sites is unknown. To examine the expression of VLA-5 during B cell development, cell lines blocked at specific stages of differentiation were evaluated for their synthesis and surface expression of VLA-5 using VLA-5-specific antibody and cDNA probes. VLA-5 mRNA and surface expression were found in the pre-B cell lines, REH and Nall 1, but not in more differentiated Raji cells or in several EBV-transformed peripheral B cell lines. Circulating peripheral B lymphocytes and resting tonsillar and splenic B lymphocytes expressed no VLA-5 by FACS analysis. Interestingly, mRNA and surface expression of VLA-5 were found in SKW, a highly differentiated, IgM-secreting line. In addition, low levels of staining for VLA-5 expression could be demonstrated when tonsillar or peripheral blood B lymphocytes were stimulated by Staphylococcus aureus Cowan (SAC). All cell lines expressed VLA-3 and VLA-4, two other receptors reported to mediate fibronectin binding in some cell types. Thus, our studies provided no evidence for developmental or inflammatory regulation of these receptors. Binding studies, however, demonstrated that adherence of both pre-B REH cells and SKW cells to fibronectin was almost completely inhibited by a monoclonal antibody to VLA-5 alpha. In addition, Raji cells, which lack VLA-5 but express VLA-3 and VLA-4, showed very low level binding to fibronectin. This demonstrates that for some B lymphocytes VLA-5, rather than other possible fibronectin receptors, primarily mediates attachment to fibronectin. These data also suggest that human VLA-5 expression is regulated during B cell development, with expression at a very early stage and then again after activation. This pattern of loss and reacquisition of an ECM receptor may be relevant to normal B cell maturation and to function during immunologic injury.

High-level direct expression of semi-synthetic human interleukin-6 in Escherichia coli and production of N-terminus met-free product

We have developed a direct expression system for high-level production of recombinant human interleukin-6 (rhIL-6) in Escherichia coli. In this system, (i) the natural N-terminal coding region of the hIL-6 gene was replaced by a synthetic sequence containing A-T rich codons, (ii) dual Shine-Dalgarno (SD) sequences were employed, (iii) an A-T rich segment was inserted in front of the initiation codon to avoid putative mRNA secondary structure in the region and (iv) the natural amber termination codon of the hIL-6 gene was changed to an ocher stop codon. The hIL-6 polypeptide, synthesized at a high level, formed cytoplasmic inclusion bodies. After refolding, the N-terminal methionine was removed by aminopeptidase-P in vitro. The purified recombinant hIL-6 had B-cell differentiation activity equivalent to natural IL-6 from a human T-cell culture.

Human CD8+ lymphocytes stimulated in the absence of CD4+ cells enhance IgG production by antibody-secreting B cells

We describe conditions where the addition of stimulated CD8+ lymphocytes from healthy donors to autologous antibody-secreting B cells significantly enhanced IgG production by these cells. In two-step experiments, purified CD8+ lymphocytes were first cocultured with irradiated allogeneic monocytes. These cells developed interleukin 2 receptors, but proliferated only minimally in the absence of CD4+ cells. When added to antibody-secreting B cells, these CD8+ lymphocytes augmented IgG production in a dose-dependent manner in comparison with control CD8+ cells. Studies with T killer cell precursors revealed an inverse correlation between augmentation of antibody synthesis and the generation of MHC class I-restricted cytotoxic activity against lymphocytes from the allogeneic donor. Evidence is presented that CD8+ CD45RA+ CD45RO- can provide B cell help, whereas the generation of CD8+ CD45RA+ CD45RO+ cells inhibits this helper activity. Our studies support the hypothesis that in chronic diseases characterized by CD4+ cell hypofunction, CD8+ cells not only fail to down-regulate antibody production, but can provide B cell help.

Defective control of Epstein-Barr virus-infected B cell growth in patients with X-linked lymphoproliferative disease

We studied the cellular function and lymphokine production of T cells from patients with X-linked lymphoproliferative disease (XLP) when activated by the challenge with Epstein-Barr virus (EBV) infection. We used an assay system in which T cells were stimulated with membrane antigens of autologous EBV-infected B lymphoblastoid cell lines (B-LCL) and we examined cellular and humoral factors derived from the stimulated T cells which control the growth of EBV-infected B-LCL. Immunoglobulin secretion from the autologous B-LCL was suppressed with radiosensitive suppressor cells in the patients with XLP. The degree of suppression was correlated with the immunoglobulin levels in the serum of the patients with acquired hypogammaglobulinaemia (P less than 0.05). In addition, T cells from the patients with XLP failed to produce interferon-gamma (IFN-gamma) (P less than 0.001). Moreover, the T cell supernatants from the patients with XLP were less potent to inhibit the B-LCL growth. This diminished inhibition of the B-LCL growth was correlated well with the decreased concentration of IFN-gamma in the T cell supernatants. These findings suggest that suppressor cells may be activated in the patients with the hypogammaglobulinaemia phenotype of XLP, but the frequent development of B cell lymphoma in hypogammaglobulinaemia indicate that immunoglobulin suppression may not exert enough pressure on the in vivo growth of EBV-infected B cells. The defective secretion of IFN-gamma may be, at least partially, responsible for the abnormal cytotoxic T cell and natural killer activities found in the patients with XLP, and may indicate the clinical evaluation about the preventive injection of IFN-gamma against the development of malignant lymphoma.

Particle concentration fluorescence immunoassay for measuring interleukin-6 receptor numbers

Analysis of the number of receptors per cell and the affinity of the ligand/receptor interaction has provided considerable insight into the functioning of numerous cytokines. Interleukin-6 (IL-6) is a multifunctional cytokine which may have considerable clinical relevance in inflammatory or immunodeficiency diseases. Using particle concentration fluorescence immunoassay (PCFIA) technology, an assay is described which calculates the receptor number and affinity on small numbers of human cells. Resting B cells are shown to lack IL-6 receptors but activation of B cells induces up to 1,300 receptors per cell, with Kd of 1 x 10(-11) to 2 x 10(-11) M. Other recombinant mediators do not alter the binding of labeled IL-6 to the cells. PCFIA avoids the use of radioactivity and requires very small numbers of cells (2 x 10(4) per well). Potential application to the study of regulatory mechanisms and to clinical situations where small samples of blood are available is feasible.

Selective suppression of lymphokine production by human hybridoma suppressor factor (HSF)

We have made a human thymus cell hybridoma that secretes an immunosuppressive monoclonal lymphokine, referred to as hybridoma suppressor factor (HSF). This factor modulates the function of CD4+ cells suppressing their IL-2 production and suppressing PWM-induced B cell differentiation into Ig producing cells. Here we have examined the effect of HSF on the generation of T cell-derived lymphokines that regulate B cell growth and differentiation as well as the expression of other proteins involved in the control of T cell growth i.e., the p55 chain of the IL-2R and the transferrin receptor (TFR). HSF suppressed IFN-gamma activity produced by mitogen-stimulated PBMC without affecting the generation of lymphokines responsible for BCGF and BCDF activities. Additionally, HSF did not inhibit the expression of either IL-2R (p55) or TFR by activated T cells in spite of causing the suppression of IL-2 production. This evidence was further supported by experiments in which HSF selectively suppressed the accumulation of IL-2 mRNA without affecting IL-2R (p55) mRNA expression in mitogen-stimulated PBMC. The selective action of HSF may help to clarify the regulatory mechanisms involved in lymphokine gene expression as well as provide a way by which immune responses involved in autoimmunity and transplant rejection may be interrupted.

A novel role for accessory cells in T cell-dependent B cell differentiation

The monocyte requirement for pokeweed mitogen-induced T cell-dependent B cell activation was reexamined. We report a dichotomy in the requirement for accessory cells in B cell proliferation and differentiation. Adherent cell-depleted human peripheral blood mononuclear cells which contained only 5% monocytes generated sufficient T cell help for optimal B cell proliferation. However, the presence of 10 to 20% monocytes were required during the last 5 days of culture for stimulated B cells to become IgG-secreting cells. Similar numbers of monocytes were also needed for anti-CD3-induced B cell differentiation. Moreover, monocytes alone added to previously activated B cells could support B cell differentiation in the absence of T cells. To determine the role of cytokines in this system, we demonstrated that supernatants of adherent cell-depleted PBMC contained decreased IL-6 activity in comparison with unseparated PBMC, but not IL-1, IL-2, or BCGF. Recombinant IL-6, however, added back either alone or with other cytokines could not replace the effects of intact monocytes on B cell differentiation. Physical interaction between the accessory cells and the responder cells was also required. As a minimum, paraformaldehyde-fixed monocytes, IL-6, and IL-1 were needed to reconstitute maximal IgG secretion. These studies suggest that accessory cells capable of producing IL-1 and IL-6 can have direct effects on the terminal differentiation of stimulated B cells.

Different induction of p55 and p70/75 interleukin-2 receptor subunits in human cells

There are two interleukin-2 receptor (IL-2R) subunits (p55 and p70/75) on human lymphocytes. Induction of the expressions of these IL-2R subunits was examined by the protein kinase-C (PK-C) activator (phorbol myristate acetate, PMA) and the calcium ionophore, ionomycine (IM). IM induced predominantly p70/75 expression on human T and B cells as indicated by the results of chemical crosslinking studies and binding assays. In contrast, PMA induced p55 expression significantly. These results suggest that the calcium-calmodulin and PK-C pathways regulate p70/75 and p55 expressions differently, and indicate that these intracellular signal messengers could control the responsiveness to IL-2, changing the affinity and number of receptors in vivo.

Demonstration and partial characterization of the interferon-gamma receptor on human B lymphocytes

The expression of interferon-gamma (IFN-gamma) receptors on normal human B cells and four B cell lines was studied. Recombinant human IFN-gamma was labeled with [gamma-32P]ATP using the catalytic subunit of a cAMP-dependent protein kinase. All four B cell lines, although differing in their responsiveness to IFN-gamma, were found to express high-affinity receptors (1,000-11,000 receptors/cell). Normal unactivated B lymphocytes were also found to express constitutively high-affinity receptors, approximately 1,400 receptors per cell with an estimated affinity of 295 pM. Activation of the normal B cells in vitro with the polyclonal B cell activator, Staphylococcus aureus Cowan strain I (SAC), resulted in a slight decline in receptor number and a more pronounced fall in receptor density. One of the B cell lines and unactivated normal B cells were shown to internalize labeled IFN-gamma rapidly. Chemical cross-linking of 32P-IFN-gamma to the CB B cell line and to freshly isolated B lymphocytes revealed one major cross-linked receptor-ligand complex which had an estimated molecular weight of approximately 110 kilodaltons. This complex corresponded to a 93 kD receptor cross-linked to recombinant IFN-gamma. Our data indicate that normal B lymphocytes constitutively express an approximately 93 kD IFN-gamma receptor which is similar to the receptor present on Epstein-Barr virus-transformed B cell lines.

Production of interleukin 6 by human spleen cells stimulated with streptococcal preparation OK-432

The streptococcal preparation OK-432 was tested for the ability to stimulate human spleen leukocytes (SPL) for generation of interleukin 6 (IL-6). When SPL were cultured with OK-432 for 24 h in serum-free T medium, the cell-free supernatant induced production of IgM in the SKW6.CL-4 and IgG in the CESS human B cell line, while no such activity was detected in unstimulated SPL culture. The activity was neutralized by treatment with antiserum directed against B cell stimulatory factor 2 (BSF-2). An optimum production of BSF-2 was observed when SPL were stimulated with 10 micrograms/ml of OK-432. The culture supernatant also induced proliferation of IL-6-dependent murine hybridoma MH-60.BSF2 (hybridoma growth factor; HGF). It is thus evident that the molecule produced by OK-432-activated human SPL is BSF-2/HGF/IL-6. These results indicate that the antitumor agent OK-432 stimulates human spleen cells to produce IL-6.

Production of B cell stimulatory factor-2/interleukin-6 activity by human endothelial cells

The effect of culture supernatants of endothelial cell (EC) lines on the immunoglobulin-M(IgM) synthesis by human B cell line, SKW6-CL4 cells, was investigated. Supernatants of human EC stimulated IgM synthesis, as high as 6-fold, but supernatants of bovine EC did not. This enhancing activity was completely blocked by addition of anti-human B cell stimulatory factor-2/interleukin-6 (BSF-2/IL-6) antibody. These data suggest that human EC might participate in the human antibody production system by producing soluble factor, BSF-2/IL-6.

Cellular and genetic analyses of IL-2 production and IL-2 receptor expression in a patient with familial T-cell-dominant immunodeficiency

Cellular and genetic analyses of interleukin-2 (IL-2) production and IL-2 receptor (IL-2R) expression were examined in a immunodeficient patient and his family members. Mononuclear cells (MNC) of the patient showed no proliferative response (stimulation index, less than 2) to T-cell mitogens (PHA and Con A) and were defective in IL-2 production and IL-2R expression (less than 1%), whereas productions of other lymphokines (B-cell differentiation factor and IFN-gamma) were not impaired significantly. His brother died of the same disease and his father also lacked in proliferative response and IL-2 production by PHA stimulation. In Southern blot analyses using DNA probes of IL-2 and IL-2R, patterns of the patient were the same as those of healthy volunteers, whereas the transcription of DNA coding for IL-2R to mRNA was lacking in the patient. These results suggest that inheritant defects of IL-2 production and IL-2R expression reside in this family and the defects are not linked to DNAs coding for IL-2 and IL-2R but to a transcriptional deficiency.

Interleukin-1 stimulation of human B-lymphoblast differentiation

Transformed B-cell lines have provided useful tools for analyzing B-cell responses to growth and differentiation factors. SKW 6.4 is a human B-lymphoblastoid line that differentiates in response to B-cell differentiation factor (BCDF) but not to other T-cell-derived lymphokines. The present studies were undertaken to determine whether monocyte-derived factors such as interleukin-1 (IL-1) could also promote the maturation of SKW 6.4 cells. Cells were cultured with and without supernatants derived from adherent monocytes of normal individuals. The number of Ig-producing plaque-forming cells in control media cultures gradually increased over a period of 4 days. Monocyte supernatants caused a 3- to 10-fold further increase in the number of IgM-secreting cells over that found in control media cultures. This stimulation by monocytes supernatants was maximal on the third or fourth day of culture and was not accompanied by an increase in proliferation. Recombinant IL-1 added to cultures of SKW 6.4 also produced a dose-related increase in the number of IgM-secreting cells without stimulating proliferation. A polyclonal antiserum against IL-1 prevented the increase in IgM-secreting cells which occurred with the addition of monocyte supernatants. Finally, IL-1 activity was detected in unstimulated SKW 6.4 supernatants. We conclude from these studies that SKW 6.4 cells both secrete IL-1 and differentiate in response to exogenous IL-1. SKW 6.4 may therefore provide a useful tool for future studies on mechanisms of IL-1-induced B cell maturation. It is possible that the basal numbers of IgM-secreting cells seen in unstimulated cultures results from an autocrine mechanism of IL-1-induced differentiation. Finally, care should be taken to exclude IL-1 from supernatants that are being tested for BCDF activity using SKW 6.4 cells.

Selective deficiency in IL-2 production and refractoriness to extrinsic IL-2 in immunodeficiency with hyper-IgM

Various lymphokines are inducible by the stimulation of T-cell mitogens, phytohemagglutinin, and concanavalin A. A 32-year-old female with an atypical type of immunodeficiency with hyper-IgM was evaluated for possible defects in the production of several immunoregulatory lymphokines. Although the mitogens appeared to bind effectively to the specific surface receptors of patient peripheral blood lymphocyte (PBL), the proliferative responses were significantly decreased. The culture supernatant of patient PBL stimulated by the mitogens contained only a trace amount of interleukin 2 (IL-2) activity. Addition of recombinant IL-2 to the cultures concomitantly with the mitogens could not restore the decreased responses of patient PBL. Tac antigen expression of patient PBL induced by the mitogens was moderately impaired. These data suggest that there is a defect in both IL-2-producing and IL-2-responding cells. In contrast, the culture supernatant of mitogen-stimulated patient PBL contained B-cell growth and differentiation factors as well as interferon-gamma activities equal to those of the control. These results suggest that there are independent regulatory pathways for the production of IL-2 and other T-cell-derived lymphokines.

Functional interleukin 2 receptors on B cells lacking Tac antigens

Human B lymphoblastoid line, SKW 6-4, cells were induced to IgM-secreting cells by high concentrations of interleukin 2 (IL 2). These cells were found to be unreactive with anti-Tac antibody and did not express mRNA detectable for Tac antigen. In Scatchard plot analysis, low-affinity IL 2-binding sites were found on SKW 6-4 cells. Moreover, analysis of the IL 2-binding molecules revealed ones (molecular weight 70,000 and 75,000) distinct from Tac antigen. It is conceivable that IL 2 exerts its effect through its interaction with these novel IL 2-binding molecules in SKW 6-4 cells.

Functional and biochemical characterization of B-cell differentiation factor (BCDF) produced by an HTLV-I-transformed human T-cell clone and demonstration of specific binding of the factor to a BCDF responsive cell line

We have previously described YA2, a human T-cell clone that secretes B-cell differentiation factor (BCDF) but not B-cell growth factor (BCGF). The BCDFs secreted by YA2 and HTLV-I-transformed YA2 (TYA2) were functionally similar in their ability to stimulate Ig secretion by Staphylococcus aureus Cowan strain I-activated B cells and IgM secretion by SKW6.4 cells. In addition, they were biochemically similar with a MW of 30 kDa by high-performance liquid chromatography (HPLC) sieving, and a pI of 6.0-6.8 by isoelectric focusing. The BCDF activity was not blocked by antibodies to interleukin 2 and BCGF. BCDF was purified from TYA2 supernatant by sequential media protein immunoadsorption, flat bed isoelectric focusing, HPLC TSK 2000 sieving, and repeated immunoadsorption and was then iodinated. The iodinated material had functional BCDF activity and migrated to a single band at MW 30 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and at pI of 6.8 by polyacrylamide gel isoelectric focusing. 125I-BCDF purified in this manner bound specifically to a BCDF-responsive cell line and not to phytohemagglutinin-activated T cells. 125I binding to the BCDF-responsive cell line was competitively inhibitable by the addition of cold BCDF. Thus we have purified and characterized a factor with BCDF activity and demonstrated that this factor binds specifically to a BCDF-responsive cell line.

The characterization of a human B cell line utilizable for the assay of B cell growth factors

An EBV-transformed B cell line JR-2(82) is described which proliferates in response to human B cell growth factor (BCGF) preparations. Although spontaneous replication occurs at high cell densities, at cell densities of 10(3) cells or less, cell death occurs in the absence of BCGF. This response is not dependent upon the presence of low concentrations of supplemental serum in the culture medium. There is no proliferative response to various preparations of interleukin (IL)-1, IL-2 or gamma-interferon (gamma-IFN) up to 1000 U/ml either alone or in combination and specific antisera to IL-2 and gamma-IFN do not interfere with the proliferative response. At 5000 U/ml of gamma-IFN or greater, a partial proliferation of the line is seen to 30% of maximal. The JR-2(82) line and its clones appear to proliferate preferentially in response to low molecular weight (LMW) BCGF, compared to the response seen to high molecular weight (HMW) BCGF from Namalwa cell line supernatants. The line does not produce Ig spontaneously but on incubation with B cell differentiation factor (BCDF) containing supernatants differentiates to an IgG-producing cell line. JR-2(82) or its derivatives may therefore provide a simple reproducible assay for BCGF in the presence of other lymphokines and may be used to study further the interactions of lymphokines in the regulation of the proliferation of EBV-transformed cells.

Age-associated changes in proliferative and differentiative response of human B cells and production of T cell-derived factors regulating B cell functions

The abilities of highly purified B cells to repeat replication for clonal expansion and to differentiate into immunoglobulin secreting cells (ISC) were examined in the aged and young groups. B cells from the aged showed twofold less proliferative response to B cell mitogen Cowan 1 (SAC) than those from the young. The original clone size of SAC responding B cells determined by colchicine block and [3H] thymidine [( 3H] TdR) uptake was not significantly reduced in the aged whereas the ability to repeat replication to expand clonal size was significantly reduced. B cells from aged and young persons were induced into ISC by combined stimulation with SAC and partially purified B cell differentiation factor (BCDF) free of IL-2 activity. ISCs for IgG and IgA were rather increased or at least not reduced in number in the aged as compared with those in the young. We also determined the IL-2 and BCDF activity produced by T cells from aged and young persons. Upon PHA stimulation, the aged T cells produced tenfold less IL-2 activity and threefold higher BCDF activity than did young T cells. Approximately threefold increase in spontaneous secretion of BCDF activity by aged T cells was found as compared with young T cells. The inverse correlation between the IL-2 activity and BCDF activity was found when both activities were determined in the same samples.

Constitutive production of B cell differentiation factor-like activity by human T and B cell lines

A lymphokine demonstrating human B cell differentiation factor (BCDF)-like activity was isolated from immature (MOLT-4f, CCRF-CEM and CCRF-HSDB-2) and mature (HUT-78) malignant human T lymphoid cell lines and from human B lymphoblastoid cell lines (BJAB and ALL-7031-B). All the cell lines were grown long term in serum-free medium. This BCDF-like activity has a molecular mass in the range of 40-60 kDa and stimulates immunoglobulin synthesis of cell lines capable of producing IgA (GM-1056), IgG (GM-1500 and CESS) and IgM (CBL#3). It was not produced by a myeloid cell line. We were only able to identify the differentiation activity produced by the T and B cell lines by using appropriate molecular mass fractions from the serum-free medium as controls. This BCDF-like activity is different from that of the human BCDF so far described as it has a higher molecular mass and is constitutively produced by malignant T lymphoid cell lines which are human T cell leukemia virus-I negative and by B lymphoblastoid cell lines.

Cloning of cDNA for human T-cell replacing factor (interleukin-5) and comparison with the murine homologue

We have cloned cDNA for T-cell replacing factor (interleukin-5), which replaces T-cell helper function for normal B cells which secrete immunoglobulin, from human T cell leukemia line, ATL-2, using mouse interleukin-5 cDNA as probe. Total nucleotide sequence of the cDNA (816 base pairs) was determined and compared with that of mouse interleukin-5 cDNA. The cloned cDNA encoded the interleukin-5 precursor of 134 amino acids containing an N-terminal signal sequence. Although the human interleukin-5 precursor is one amino acid longer than the murine homologue, the sizes of the mature proteins appear similar. The nucleotide and amino acid sequence homologies of the coding regions of human and murine interleukin-5 are 77% and 70%, respectively. Human interleukin-5 synthesized by the direction of the cloned cDNA induced immunoglobulin synthesis in human B cells stimulated by Staphylococcus aureus mitogen.

Independent regulation of B-cell inducing factor and IL-2 production by T lymphocytes, and direct and indirect promotion of immunoglobulin secretion by glucocorticosteroid

The conditions for induction of B-cell inducing factor (BIF) by human peripheral blood T cells was investigated. BIF was assayed by induction of immunoglobulin secreting cells (ISC) in peripheral blood B (non-T) cells stimulated with Staphylococcus aureus bacteria strain Cowan I (Sac), and in the IgM cell line SKW6.4. Maximum BIF production occurred with high concentrations of the T-cell mitogens phytohemagglutinin, concanavalin A, and PWM. Dexamethasone (Dex) also induced BIF production in T cells at 10(-5) to 10(-7) M. At 10(-5) and 10(-6) M Dex, the T-cell supernatants had to be dialyzed before testing because Dex alone stimulated variable levels of ISC in both test B-cell assays. Dex did not enhance BIF production by T cells that were optimally stimulated by lectin. BIF levels were maximum by Day 2 of T-cell cultures and remained high at Days 3 and 4. In contrast, IL-2 reached a peak at Day 1 and declined drastically by Day 4. We previously showed that IL-2 at less than 100 U/ml did not induce ISC in B cells and did not alter ISC induction by BIF. Dex did not induce IL-2 production and inhibited IL-2 production induced by Con A, in contrast to the promoting effects of Dex on BIF production, providing further evidence for the independence of BIF and IL-2 production and B-cell stimulation.

Monoclonal antibodies against antigens on breast cancer cells

Of 360 mAb obtained in a cell fusion experiment with the spleen cells of a mouse immunized with a mixture of different human breast carcinoma cell lines, 30 mAb were selected which reacted more strongly with tumor cells than with (noncancerous) fibroblasts. These mAb were tested for reactivity with additional types of cancerous and noncancerous tissues. Two mAb showed high tumor selectivity, but the corresponding epitopes on individual tumor cells were heterogeneously expressed. The mAb will be evaluated for in vivo applications.

Spontaneous immunoglobulin A secretion and lack of mitogen-responsive B cells in systemic lupus erythematosus

In an analysis of lymphocyte functions of systemic lupus erythematosus (SLE) patients, B cell abnormalities such as a lack of mitogen-responsive B cells and a predominance of spontaneous IgA-secreting cells (SC) were found. Lymphocyte functions of 20 SLE patients were studied. Impaired proliferative response to B cell mitogen, Staphylococcus aureus strain Cowan I (Cowan I), was observed, whereas the response to T cell mitogen phytohemagglutinin was normal. High levels of spontaneous IgA-SC were observed in SLE patients (greater than 10(2) cells/10(4) peripheral blood mononuclear cells [PBMC]), whereas spontaneous IgM-, IgG-, or IgE-SC were not proportionately increased. The number of spontaneous IgA-SC decreased with time in culture and became undetectable by day 5 of culture. In contrast, spontaneous immunoglobulin- (IgM, IgG, and IgA) SC were not observed in healthy volunteers (less than 10 cells/10(4) PBMC). Moreover, in SLE patients failure of induction of immunoglobulin-secreting cells (ISC) was observed when B cells were stimulated by Cowan I and B cell differentiation factor at any day tested, whereas ISC were induced in healthy volunteers on day 6 of culture. Depletion of T cells or macrophages did not affect the results obtained. These results suggest that the abnormalities observed in SLE B cells are not due to the in vitro direct effects of suppressor macrophages or suppressor T cells, and that the condition of the predominance of spontaneous IgA-SC and the unresponsiveness to exogenous stimulation may be emblematic of hyperactive B cells in SLE.

Purification to homogeneity and characterization of human B-cell differentiation factor (BCDF or BSFp-2)

Human B-cell differentiation factor (BCDF) was purified to homogeneity by sequential filtration and chromatography of culture supernatants from TCL-Na1 cells on an AcA34 gel column and then on a Mono P column with fast protein liquid chromatography and reversed-phase HPLC. A 5300-fold enrichment in specific activity of BCDF with about 25% recovery was attained. The homogeneity of purified BCDF was evidenced by the following: (i) the specific activity was 1.7 X 10(7) units/mg of protein, (ii) only two bands, Mr 19,000 and 21,000, were identified by NaDodSO4/PAGE under reduced as well as nonreduced conditions, and (iii) BCDF activity was recovered from the gel after NaDodSO4/PAGE in the fractions corresponding to protein bands of Mr 19,000 or 21,000. Purified BCDF induced Ig secretion in Epstein-Barr virus-transformed cell lines; as little as 3 pM gave 50% of the maximum reaction achieved by 30-80 pM BCDF. Purified BCDF induced Ig production in activated B cells without any effect on cell growth. Purified BCDF did not show any activity of interleukin 1 or 2, B-cell stimulatory factor (BSF)p-1, B-cell growth factor II (BCGF-II), or interferon. Since BCDF was isolated and characterized as described, we propose that the BCDF that induces the final differentiation of B cells into high-rate Ig-secreting cells be designated BSFp-2.

T cell-replacing factor in specific antibody responses to influenza virus by human blood B cells

In man, B cell maturation factors obtained from T cells or T cell lines have been shown to induce antibody formation in mitogen or anti-immunoglobulin activated B cells, and in some continuous B cell lines, but the relationships between these factors and B cell differentiation factors in antigen-specific antibody responses is unclear. We have now shown that supernatants from phytohemagglutinin-activated tonsil cells, or from the Gibbon Ape T cell line MLA-144, can substitute for T cells in the specific antibody response by human blood B cells to influenza virus. Thus, T cell-depleted non-rosette-forming (E-) cells prepared from peripheral blood mononuclear cells made antibody when cultured with antigen and factor together, whereas control cultures of E- cells with either antigen or factor alone did not. Moreover, E- cells cultured with factor and influenza virus strain A/X31 made antibody to A/X31, but not the non-cross-reacting strain, B/HK (and vice versa) showing that the response was antigen specific. The activity in these supernatants, therefore, fulfilled the functional definition of T cell-replacing factor (TRF). The possibility that interleukin 2 (IL 2) present in the TRF-containing supernatants was expanding residual T cells in the E- preparations to provide normal T cell help was excluded in three different ways. First, E- cells depleted of T (Leu4+) cells to undetectable levels made normal amounts of antibody when cultured with antigen and TRF. Secondly, a limiting dilution technique was employed to show that help in cultures of E- cells and TRF was not mediated by antigen-specific T helper cells. Thirdly, TRF-containing supernatants depleted of IL2 retained activity, whereas purified IL2 was inactive. Preliminary purification of TRF by gel filtration on Ultrogel AcA54 columns showed that all the activity eluted in a single peak between 35 000 and 43 000 molecular weight. This distinguishes human TRF from IL 2 and from other B cell maturation factors with a molecular weight range of 15 000-20 000 which act on continuous B cell lines. In addition to TRF, supernatants from phytohemagglutinin-activated tonsils also contained a factor which could induce polyspecific IgM production, but only in cultures containing significant numbers of T cells. This additional activity may have been due to IL 2, and provides an explanation for the apparent T cell-dependent effects sometimes observed in experiments designed to test B cell differentiation factors on T cell-depleted normal B cells.

The role of B cell differentiation factors and specific T cell help in the pathogenesis of primary hypogammaglobulinemia

We have examined the function of T and B cells from patients with late onset primary acquired hypogammaglobulinemia (PHG). T cells from these patients give effective help to normal B cells for antigen-dependent antibody synthesis. PHG mononuclear cells also synthesize normal quantities of B cell differentiation factors, which enhance IgG, IgM and antigen-dependent antibody synthesis by normal lymphocytes. While patient T cells appear to behave appropriately, the responsiveness of patient B cells is abnormal. Although they respond to differentiation factors with increased synthesis of IgM, overall levels are 10-50-fold lower than normal B cells, and they produce little or no IgG. This pattern of response is not altered if normal T cells are the source of help. The poor response of the B cell appears to represent immaturity rather than an inherent defect, as IgG-secreting clones can be obtained after Epstein-Barr virus transformation of lymphocytes from certain patients, and some of these clones respond to differentiation factors with increased IgG production. The lack of any functional defect in the T population, and the apparent immaturity rather than abnormality of the B cells, may implicate accessory cells in the pathogenesis of the disease.

Human lymphoblastoid cell line producing protective monoclonal IgG1, kappa anti-tetanus toxin

Peripheral blood lymphocytes from an individual, recently boosted with tetanus toxoid (TT), were transformed with Epstein-Barr virus. No antigen-specific selection nor stimulation of B cells was performed prior to transformation. One stable cell line, designated CLB-Hu-TT-1, was established. This cell line has a doubling time of 24 h and yields 10 micrograms/ml of a monoclonal IgG1, kappa anti-TT antibody in bulk cultures. The antibody is biologically active in that it can protect mice against the effects of tetanus toxin. The cell line has been characterized with regard to some cytoplasmic and membrane markers.

Lymphokine factors inducing IgG production in human B-cell line ARH-77 and stimulatory effects of phorbol ester tumor promoter

Regulation of immunoglobulin-secreting cells (ISC) was studied in human IgG B-cell line ARH-77, as assayed by reverse plaque formation. Numbers of ISC were stimulated by both lymphokine (stimulation index = 1.5-8.7) and phorbol myristic acetate (PMA) (stimulation index = 2.7-42). Incubation of ARH-77 with the two agents together caused additive or super-additive numbers of ISC, suggesting that they acted on this B cell via different mechanisms. B-cell-inducing factors stimulating IgG ISC in ARH-77 line were found at 20,000 and 40-60,000 molecular mass. The 20-KDa factor could be distinguished from IL-2 by affinity chromatography on blue agarose. Stimulated cells maintained their immunoglobulin class, and no evidence for isotype switching to IgM or IgA was detected using lymphokine or PMA. The cell line is a model for normal B lymphocytes which have been activated, for example, by Staphylococcus bacteria, to respond to T-cell factors.

IgM and IgG secretion in human B-cell lines regulated by B-cell-inducing factors (BIF) and phorbol ester

Human B-cell lines were screened for stimulation of immunoglobulin production by incubation with lymphokine (LK) or tumor promoter, phorbol myristic acetate (PMA). One group of lines had essentially no immunoglobulin-secreting cells (ISC) under any condition (less than 0.01%), detected by a reverse plaque assay. Another group of lines had high levels of ISC (greater than 5%) which was not increased substantially by inducing agents. In a third group of IgM and IgG lines, there were intermediate levels of ISC which could be increased by LK, PMA or both agents. No evidence for isotype switching in a number of stimulated IgM and IgG cell lines was detected. Clone SKW6.4 of an IgM line was highly responsive to a B-cell-inducing factor (BIF) in LK. BIF for SKW6.4 and IgG line ARH-77 was weakly binding to DEAE cellulose, about 20,000 mol. wt., and separable from IL-2 by blue agarose chromatography. IL-2 did not stimulate secretion in SKW6.4 with or without purified BIF. In Clone SKW6.4, BIF stimulated ISC per recovered cell up to 30-fold by day 1 of culture, and these plateau levels of about 6% ISC were maintained for longer than 4 days. Treatment of cells with BIF for less than 1 day was sufficient to produce maximum effect on this clone for the succeeding 4 days. Cells stimulated with BIF and then subcultured at day 3 without BIF showed ISC numbers increasing but at a slower rate than the total population, suggesting that the induced differentiation state is long-lived (half-life of % ISC greater than 6 days) and that ISC produce some daughter ISC.(ABSTRACT TRUNCATED AT 250 WORDS)