High yields of specific hybridomas obtained by electrofusion of murine lymphocytes immunized in vivo or in vitro

Sympathetic nervous system control of anti-influenza CD8+ T cell responses

Despite the longstanding appreciation of communication between the nervous and the immune systems, the nature and significance of these interactions to immunity remain enigmatic. Here, we show that 6-hydroxydopamine-mediated ablation of the mouse peripheral sympathetic nervous system increases primary CD8(+) T cell responses to viral and cellular antigens presented by direct priming or cross-priming. The sympathetic nervous system also suppresses antiviral CD4(+) T cell responses, but this is not required for suppressing CD8(+) T cell responses. Adoptive transfer experiments indicate that enhanced CD8(+) responses do not result from permanent alterations in CD8(+) T cell function in sympathectomized mice. Rather, additional findings suggest that the sympathetic nervous system tempers the capacity of antigen-presenting cells to activate naïve CD8(+) T cells. We also show that antiviral CD8(+) T cell responses are enhanced by administration of a beta(2) (but not beta(1) or alpha) adrenergic antagonist. These findings demonstrate a critical role for the sympathetic nervous system in limiting CD8(+) T cell responses and indicate that CD8(+) T cell responses may be altered in patients using beta-blockers, one of the most widely prescribed classes of drugs.

Cephalin as an efficient fusogen in hybridoma technology: can it replace poly ethylene glycol?

In this study we set up a simple, fast, and highly efficient protocol to fuse cells and produce human hybridoma using non-toxic cephalin as a fusogenic lipid. We compared our proposed method with PEG-mediated fusion, the well-known conventional method. Human lymphoblastoid cells were fused with an F3B6 heteromyeloma cell line using cephalin or PEG as the fusogenic compound. The viability of the cells and their fusion rate were determined microscopically and hybridoma (antigen-specific and non-specific) production yield was calculated following HAT selection and screening. The fusion rates of cells in cephalin and PEG-mediated methods were comparable (25.9+/-5.73% versus 27.3+/-6.07%) while the viability of the cells immediately and after overnight incubation was obviously greater in the cephalin method than in the PEG (p<0.001). Our proposed cephalin-mediated cell fusion method is about five times more efficient than PEG in production of hybridoma clones; thus it may dismiss PEG as the most generalized fusogen in the future.

Among B cell non-Hodgkin's lymphomas, MALT lymphomas express a unique antibody repertoire with frequent rheumatoid factor reactivity

We analyzed the structure of antigen receptors of a comprehensive panel of mature B non-Hodgkin's lymphomas (B-NHLs) by comparing, at the amino acid level, their immunoglobulin (Ig)V_H-CDR3s with CDR3 sequences present in GenBank. Follicular lymphomas, diffuse large B cell lymphomas, Burkitt's lymphomas, and myelomas expressed a CDR3 repertoire comparable to that of normal B cells. Mantle cell lymphomas and B cell chronic lymphocytic leukemias (B-CLLs) expressed clearly restricted albeit different CDR3 repertoires. Lymphomas of mucosa-associated lymphoid tissues (MALTs) were unique as 8 out of 45 (18%) of gastric- and 13 out of 32 (41%) of salivary gland-MALT lymphomas expressed B cell antigen receptors with strong CDR3 homology to rheumatoid factors (RFs). Of note, the RF-CDR3 homology without exception included N-region–encoded residues in the hypermutated IgV_H genes, indicating that they were stringently selected for reactivity with auto-IgG. By in vitro binding studies with 10 MALT lymphoma–derived antibodies, we showed that seven of these cases, of which four with RF-CDR3 homology, indeed possessed strong RF reactivity. Of one MALT lymphoma, functional proof for selection of subclones with high RF affinity was obtained. Interestingly, RF-CDR3 homology and t(11;18) appeared to be mutually exclusive features and RF-CDR3 homology was not encountered in any of the 19 pulmonary MALT lymphomas studied.

Generation of class-selective monoclonal antibodies against the penicillin group

To develop a penicillin-specific ELISA, different attempts were made to obtain monoclonal antibodies specific for the common structure of penicillins. Ampicillin was coupled to different carrier proteins (bovine serum albumin, chicken ovalbumin, and thyroglobulin) to render it immunogenic. Different coupling methods were compared: two methods using a cross-linker (glutaraldehyde or a succinimide ester), one carbodiimide-mediated coupling method, and one method without any cross-linker or mediator molecule (physiological binding). Mice were immunized with the conjugates intraperitoneally or in the footpad. A screening ELISA was developed to detect anti-ampicillin antibodies in sera. Specificity and affinity of the antibodies were demonstrated by inhibiting their binding with a 10 mM solution of ampicillin. No difference could be observed using electrofusion or PEG-mediated fusion. For the production of the monoclonals, an intravenous final boost gave antibodies with better specificity and affinity than an intraperitoneal final booster injection. At least one anti-ampicillin monoclonal antibody (19C9) cross-reacts with penicillin G, oxacillin, dicloxacillin, and carbenicillin, and not with sulfanilamide, chloramphenicol, neomycin, and streptomycin, and is therefore considered interesting for developing a penicillin-specific ELISA.

Mammalian cell fusion in an electroporation device

We and others have been interested in the phenomenon of gene 'extinction' in somatic cell hybrids, reasoning that the study of this process is likely to reveal underlying mechanisms responsible for limiting the expression of specialized genes only to appropriate cell types. In the course of our studies in this area, we have developed a simple and economical method of fusing mammalian cells, using an electroporation device. In fusions between murine myeloma and T lymphoma lines, hybrid cell recoveries were typically one per 10(5) [corrected] input myeloma cells. Because of our interest in the regulation of immunoglobulin heavy chain (IgH) gene expression, we analyzed the hybrids for both IgH gene composition and expression. The hybrid lines were phenotypically indistinguishable from those generated by the more conventional, polyethylene glycol (PEG)-induced fusion protocol. There was a notable increase, however, in the number of hybrids that retained IgH-encoding chromosomes from both parental lines.

A rapid non-selective method to generate quadromas by microelectrofusion

A simple non-selective methodology was developed and standardized to generate desired hybrid-hybridoma or quadroma secreting bifunctional antibodies. This novel protocol is based on microelectrofusion on a meander chamber using a few hundred cells of each of the two parental hybridomas with no laborious drug selection procedures. Seeding approximately 10 cells per well in a 96-well microtitre plate after fusion in 200 microliters standard medium containing 20% FBS and 10% Origen growth factor generated positive quadromas secreting bispecific antibodies with good stability after the second reclone. Compared to the conventional PEG fusion and other methods this simple protocol is both rapid and economical. Generally, conventional methods to make quadromas and triomas require the introduction of drug selection markers into one or both of the parental cells, a procedure that could take 3-6 months. Utilizing the non-selective microelectrofusion method described here, we have generated several quadromas in a very short time. Further, such a protocol could also be potentially adopted to generate human hybridomas with few B cells isolated from peripheral blood lymphocytes enriched by antigen specific panning or affinity microelectrofusions.

Immortalization of antigen selected B cells

This paper reports the generation of monoclonal antibody producing hybridomas from a small number of antigen-specific B cells selected by panning on antigen-coated dishes and rosetting with antigen-coupled paramagnetic beads. Anti-HIV positive B cells from spleen could be recovered by panning with an efficiency of 5% and a purity of 24%. Immunobead selection of anti-HIV positive B cells from the same mice yielded a recovery of 17% and a purity of 7%. Various experimental conditions with respect to the selection of specific B cells were investigated, leading to an optimized protocol for the isolation of a limited subset of B cells. The selected cells retained their property to produce immunoglobulins and could be clonally expanded in the presence of human T cell supernatant and irradiated murine thymoma helper cells to generate sufficient cells for a mini-electrofusion with NS-1 myeloma cells. Up to 78 specific hybridomas could be generated from one anti-HIV positive B cell. An overall efficiency of specific B cell immortalization of up to 10% was obtained.

A human monoclonal antibody, produced following in vitro immunization, recognizing an epitope shared by HLA-A2 subtypes and HLA-A28

In vitro immunization and subsequent immortalization of peripheral blood cells of a multiparous woman has resulted in the production of a stable human mouse heterohybridoma, 5C2A2, secreting an HLA-A2/A28-specific human monoclonal antibody. Although possibly exposed to HLA-A2 by transfusions, the cell donor showed no HLA-A2-specific serum antibodies. The present protocol for in vitro immunization includes the elimination of suppressor cells from the responder cell population, the presence of irradiated allogeneic lymphocytes as a source of antigen, as well as stimuli--recombinant interleukin-2 and a B-cell specific nucleoside analogue--causing the proliferation of B lymphocytes, prior to immortalization. The ability of the antibody 5C2A2 to detect all known HLA-A2 subtypes, except A2.3, and A28, allows identification of the serological epitope on the HLA-A2 molecule. Application of this in vitro immunization method allows the production of a set of HLA monoclonal antibody-secreting human hybridomas, independent of the existence of serum HLA antibodies in the lymphocyte donors.

An efficient procedure for the generation of human monoclonal antibodies based on activation of human B lymphocytes by a murine thymoma cell line

A new, efficient procedure for the generation of human monoclonal antibodies has been developed. The procedure is based on the activation of human B cells in microwells by murine thymoma EL4B5 cells. This mode of B cell stimulation leads to proliferation of at least one per eight of human B cells and to a high rate of antibody production. Subsequently, supernatants of the microwells are screened by ELISA for the presence of antibody of the desired specificity and B cells from selected wells are hybridized by electroporation. To optimize the procedure, the kinetics of the B cell expansion induced by EL4B5 cells were analysed. Counting and phenotyping of cultured cells at different time points indicated that the peak of B cell expansion occurred at day 5 for tonsil B cells (16-fold increase) and at day 7 for peripheral blood B cells (20-fold increase). The B cells did not merely proliferate but also differentiated, as indicated by loss of CD20 expression and increase of CD38 expression. At the peak of B cell expansion, B cells could be hybridized efficiently with myeloma cells. The majority of the resultant hybridomas secreted human immunoglobulin. The efficiency of the procedure is exemplified by the generation of hybridomas secreting human IgG against Haemophilus influenzae from limited numbers of either human tonsil B lymphocytes or peripheral blood B lymphocytes.

Characterization of two human monoclonal antibodies reactive with HLA-B12 and HLA-B60, respectively, raised by in vitro secondary immunization of peripheral blood lymphocytes

We have developed an in vitro immunization system for the production of B-cell lines that secrete HLA-specific human mAbs. For this purpose, peripheral blood lymphocytes of parous women were stimulated with pools of allogeneic lymphocytes. Preferential outgrowth of B-lymphocytes was effected by inclusion of rIL-2 and a B-cell specific nucleoside analogue. Stimulated B cells were immortalized by EBV transformation, and specific antibody-producing transformants were fused to heteromyeloma or mouse myeloma cell lines, yielding stable hybridomas. This approach has led to the successful development of two human heterohybridomas producing HLA-specific mAbs reactive by complement-mediated cytotoxicity. The specificities of these human mAbs, reactive with HLA-B12(44 + 45) and HLA-B60, respectively, are fully concordant with those of HLA-typing sera.