Production of murine monoclonal antibodies against human thyroglobulin using an in vitro immunization procedure in serum-free medium

Osteoblastic differentiation

The fully differentiated osteoblast may be easily recognized in bone tissue. Its cuboidal shape, its position directly opposed to the bone surface and its capacity to produce calcified bone matrix are characteristic. Three other differentiation stages are also reasonably well defined--the preosteoblast, the osteocyte and the lining cell. These differentiation stages are preceded by an unknown number of precursor, progenitor and stem cell stages. Little is known about the regulation of the transitions between the various osteogenic phenotypes and their reversibility or irreversibility. One of the reasons for this is the lack of adequate tools with which to recognize the various differentiation stages. We have developed a number of monoclonal antibodies (in bone) specifically directed against osteocytes, osteoblasts and as yet unidentified cells in the periosteum. The anti-osteocyte monoclonals were used to recognize osteocytes in bone cell cultures and we obtained purified osteocyte populations for metabolic studies. Osteocytes were shown to have binding sites for parathyroid hormone. The antibodies directed against osteoblasts showed that at present our culture conditions are inadequate to allow osteoblast differentiation in vitro.

New approaches for the development and application of monoclonal antibodies for the diagnosis and therapy of human cancer

Monoclonal antibodies (MAbs) represent potentially important reagents for both the diagnosis and therapy of human cancer. Innovative approaches are resulting in the improved production of MAbs and an enhanced ability to use these molecules therapeutically. Application of genetic engineering to MAb development is also resulting in the production of MAbs displaying enhanced target specificity. Of particular value for cancer therapy will be catalytic, bispecific, anti-idiotypic and human MAbs. By using agents that can augment the expression of tumor-associated antigens on cancer cells, a further increase in the utility of MAbs in cancer therapy will be forthcoming.

In vitro immunization of rat spleen lymphocytes with Forssman glycosphingolipid antigen and the generation of a monoclonal antibody

A procedure for in vitro immunization of splenic lymphocytes with a glycolipid antigen is described. Culture medium supernatant of ConA- and PHA-stimulated spleen cells and that of Con A-stimulated human Jurkat T cell line (IL-2-rich medium) were used as sources of cytokines to support T and B cell stimulation, and anti-mu was used to support B cell differentiation. Unprimed rat spleen cells (2 x 10(6)/ml) were stimulated with 2 micrograms/ml Forssman glycolipid antigen coupled to Sepharose for 4 days. The cells were fused with a mouse myeloma cell line P3-X63-Ag8-U1. At initial screening, 12% of the colony forming wells were secreting specific antibody. After cloning, a stable hybridoma cell line (designated 4C3) was established which secreted a monoclonal IgM antibody directed against the carbohydrate moiety of Forssman glycosphingolipid (GalNAc alpha 1-3GalNAc beta 1-3Gal alpha 1-4Gal beta 1-4Glc-ceramide).

Identification of structural differences between different forms of interleukin-2 (IL-2) using anti-(human recombinant) IL-2 monoclonal antibodies

We have generated a panel of murine monoclonal antibodies (mAbs) directed against recombinant human interleukin-2 (rh IL-2). All mAbs have similar affinities (Kaff approximately equal to 10(-8) M) and are of the IgG1 isotype. Specificity of the mAbs has been established using an ELISA method and immunoprecipitation of native human interleukin-2 (nh IL-2) present in supernatants from PHA-stimulated human mononuclear cells (PBMNC). Four of the nine mAbs inhibit the rh IL-2-dependent proliferation of a murine cytotoxic T-lymphocyte line (CTLL-2). The estimated ID50, in the presence of 0.75 IU rh IL-2/ml, ranges from 2.0 micrograms/ml to 30 micrograms/ml final concentrations of the antibodies. Using different forms of IL-2 we found that the mAbs give different patterns of inhibition of the IL-2-dependent proliferation. One mAb (AMCIB 27) is able to discriminate between rh and nh IL-2. Findings with another mAb (AMCIB 24) indicate that possible functional differences between human IL-2 and recombinant murine (rm) IL-2 are caused by differences in the active sites. The results of this investigation show that it is possible to obtain mAbs, after immunization with rh IL-2, that differ in their ability to inhibit the biological action of different forms of IL-2.

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

We have studied the use of electrofusion to obtain hybridomas producing antigen-specific antibodies after immunization of murine lymphocytes in vitro. Under optimal conditions fusion frequencies of the order of magnitude of 10(-3) were obtained, which is approximately 80-fold higher than the mean value obtained with fusion induced by polyethylene glycol. The number of antigen-specific hybridomas was also increased in a comparable way. The high yields of specific hybridomas observed with electrofusion were independent of the immunization procedure, the antigen or the hapten of interest, or the sources of the lymphocytes. The data presented in this paper indicate that electrofusion may be an extremely attractive alternative method for immortalization of human lymphocytes following immunization in vitro.

Optimal conditions for the generation of monoclonal antibodies using primary immunisation of mouse splenocytes in vitro under serum-free conditions

We have further optimised the serum-free in vitro immunisation system described by Ossendorp et al. (J. Immunol. Methods 91, 257, 1986) for the generation of hybridomas secreting specific antibodies. Thyroglobulin and the hapten 2-phenyl-5-oxazolone coupled to chicken serum albumin were used as antigens. For an optimal outgrowth of antigen-specific B cells the presence of T cells, thymocyte-conditioned medium and antigen are required. The addition of supernatant from EL-4 cells (stimulated by phorbolmyristate acetate) inhibits the outgrowth of antigen-specific B cells. Using six-well plates with a surface area of 10 cm2 per well, an optimal IgM response was obtained when 10(7) splenocytes in a total volume of 2 ml/well were cultured for 3 days in the presence of antigen and thymocyte-conditioned medium. Increasing the concentration of cells whilst maintaining a constant surface area resulted in a decreased response.

Efficient selection of high-affinity B cell hybridomas using antigen-coated magnetic beads

A method for the selection of antigen-specific B cell hybridomas using antigen-coated magnetic beads is described. Stable B cell hybridoma cell lines directed against human thyroglobulin were incubated with thyroglobulin-coated beads. 2 h of incubation at 4 degrees C using bead-to-cell ratios of at least 3:1 were found to be the optimal conditions for rosette formation. Rosettes were efficiently isolated with a strong magnet. Rosette formation was antigen-specific since irrelevant hybridoma cell lines could not form rosettes, nor could BSA-coated or uncoated beads form rosettes. Free antibodies produced by the hybridoma cells were able to block rosette formation. Blocking of rosette formation permitted the identification of different and overlapping epitopes recognized by four different hybridomas. Using six stable hybridoma cell lines with different affinities for thyroglobulin, rosette formation appeared to be dependent on the affinity of the immunoglobulin membrane receptor for antigen. A correlation was observed between the affinity of the secreted antibodies and the capacity of the hybridomas to form rosettes, suggesting that this method is suitable for the selection of hybridomas producing antibodies with a high affinity for the antigen. Antigen-coated magnetic beads were found to be suitable for the efficient selection of thyroglobulin-specific hybridoma cells from bulk cultures shortly after fusion. A 300-fold enrichment of thyroglobulin-specific cells was obtained using this method.

Production and isolation of large quantities of monoclonal antibody using serum-free medium and fast protein liquid chromatography

A method for the production and purification of monoclonal antibody on a large laboratory scale is described. It involves the growth of monoclonal antibodies in serum-free medium, ultrafiltration through an Amicon XM100A filter and fast protein liquid chromatography on a mono Q column with an ionic strength and pH elution gradient. Up to 30 mg of antibody per litre of cell culture supernatant was purified in one day. The procedure can be carried out at 4 degrees.

In vitro stimulation of immune spleen cells enhances the number of anti-lipid A-producing hybridomas

An in vitro stimulation method for the generation of hybridomas producing antibodies with specificity for the weakly immunogenic lipid A is described. Conditions influencing in vitro stimulation of immune spleen cells were investigated. Depending on the experimental conditions the percentage of specific antibody-producing hybridomas varied between 0 and 39%. Most successful was stimulation with both antigen and the synthetic adjuvant muramyl dipeptide (MDP) for 3 days. In vitro stimulation of spleen cells from animals classically immunized with Salmonella Re mutant enhanced the number of lipid A-specific IgG-producing hybridomas from six after direct fusion to 17 after stimulation. These experiments indicate that the synergistic action of antigen and MDP is caused by preferential action on antigen selected B cells.

Cross-reactivity of mouse monoclonal antibodies produced by in vitro or in vivo immunization

The effect of different immunization schemes on the resulting antibody specificity was investigated. The cross-reactivity of monoclonal antibodies produced by in vitro vs. in vivo immunization was tested, using a solid phase enzyme immunoassay. Ten different monoclonal antibodies were tested against 15 different antigens. There was no difference in cross-reactivity between the two types of antibodies when tested against antigens coated onto the plastic wells in a buffer solution. When the antigens were dried onto the plastic wells the IgM monoclonal antibodies produced by in vitro immunization exhibited a somewhat different reactivity pattern. However, the assay design was shown to be of more importance than the immunization procedure when determining antibody specificities.

Requirements for the generation of memory B cells in vivo and their subsequent activation in vitro for the production of antigen-specific hybridomas

We have studied the conditions required for the activation in vitro of memory B cells generated in vivo. BALB/c mice were immunised by a single injection of antigen emulsified in Freund's complete adjuvant. Splenocytes were isolated after different time intervals and cultured in a serum-free medium in the presence of antigen and thymocyte-conditioned medium. After 3 days the splenocytes were fused with myeloma cells. A minimum time interval of more than 2 weeks between priming in vivo and stimulation in vitro was required in order to obtain antigen-specific IgG-secreting hybridomas. After a time interval of 4 weeks or longer most of the antigen-specific hybridomas secreted IgGs. During stimulation in vitro the presence of antigen and of T cells was found to be essential for obtaining an antigen-specific IgG response. The addition of thymocyte-conditioned medium enhanced the IgG response.

Clinical laboratory applications of monoclonal antibodies

Monoclonal antibody (MAb) technology is well recognized as a significant development for producing specific serologic reagents to a wide variety of antigens in unlimited amounts. These reagents have provided the means for developing a number of highly specific and reproducible immunological assays for rapid and accurate diagnosis of an extensive list of diseases, including infectious diseases. The impact that MAbs have had in characterizing infectious disease pathogens, as well as their current and future applications for use in clinical microbiology laboratories, is reviewed. In addition, the advantages (and disadvantages) of the use of MAbs in a number of immunoassays, such as particle agglutination, radioimmunoassays, enzyme-linked immunosorbent assays, immunofluorescent-antibody assays, and immunohistology, are explored, including the use of these reagents in novel test system assays. Also, nucleic acid probe technology is compared with the use of MAbs from the perspective of their respective applications in the diagnosis of infectious disease agents. There is no question that hybridoma technology has the potential to alter significantly the methods currently used in most clinical microbiology laboratories.

Monoclonal antibody 123C3, identifying small cell carcinoma phenotype in lung tumours, recognizes mainly, but not exclusively, endocrine and neuron-supporting normal tissues

Monoclonal antibody (MAb) 123C3 was raised against a membrane preparation of a small cell lung carcinoma (SCLC) specimen and its reactivity on normal tissues was tested. For the endocrine system, positive tissues included: pituitary and adrenal glands, thyrocytes and C-cells of the thyroid, the parathyroids, testis Leydig cells and pancreatic islets. In bronchioles and intestinal epithelium occasional cells, resembling Kultchitsky and enterochromaffin cells, were also positive. Epithelia like rete testis, mammary epithelium and gastric mucosa were positive in all or a significant proportion of cells. The positive cells in mammary epithelium and gastric mucosa were too numerous to represent the endocrine cells only. Neurons were usually negative or weakly positive. Their supportive cells such as glial, Schwann and ganglionic satellite cells were positive. Mesenchymal cell types, such as smooth muscle cells in most organs, cardiac muscle cells, the pia-arachnoid and ovarian stroma cells were positive, indicating that 123C3 reactivity is not confined to epithelial and neuron-supporting tissues. In Western blots of tumour specimens 123C3 recognized a 29 kDa band in reducing conditions, shifting to approximately 150 kDa in non-reducing conditions. Immunofluorescence on live tissue culture cells demonstrated presence of the antigen on the cell surface.

Characterization of five monoclonal antibodies obtained after immunization in vitro with a synthetic 19-amino acid peptide of thyroglobulin

A 19-amino acid synthetic peptide representing the highly conserved amino terminus of thyroglobulin was used for the production of monoclonal antibodies after immunization of splenocytes in vitro. The properties of five of the antibodies were studied. One reacted only with the synthetic peptide. The others reacted with both the synthetic peptide and with thyroglobulin from all species tested so far, confirming that the amino terminus of thyroglobulin is highly conserved. Two of the five antibodies showed a positive reaction when tested on frozen sections of thyroid tissue, but with different reaction patterns. Monoclonal antibody F4 gave a positive reaction in the colloid, which contains mainly 19S thyroglobulin. In contrast, monoclonal antibody G4 gave a positive reaction only in the follicular cells. Monoclonal antibody G4 binds primarily to low molecular weight compounds in thyroglobulin preparations, possibly representing breakdown products of the protein.

Direct evidence for a primary immune response of murine B-lymphocytes after in vitro immunization of dissociated splenocytes

Monoclonal antibodies against human thyroglobulin were generated using splenocytes cultured in vitro with the antigen. When splenocytes from non-immunized mice were used, about 90% of the hybridomas obtained produced immunoglobulins of the IgM class. In contrast, when splenocytes from mice previously immunized in vivo with human thyroglobulin were cultured in vitro with the antigen about 85% of the hybridomas obtained produced immunoglobulins of the IgG class. The properties of the monoclonal antibody produced by hybridoma 3D12, obtained after culturing splenocytes from non-immunized mice with human thyroglobulin, were examined in detail. Monoclonal antibody 3D12 reacted only with human thyroglobulin and not with the murine homologue in an enzyme-linked immunosorbent assay, in immunoblotting experiments and in an immunohistochemical test. These results provide direct evidence that a primary response to an antigen can be elicited by adding the antigen to cultures of splenocytes from non-immunized mice.

Development of in vitro immunization in murine and human hybridoma technology

The development of in vitro immunization in murine and human hybridoma technology is reviewed. Special consideration is given to: technical aspects of in vitro immunization of mouse B cells; quality of antibodies produced by in vitro immunization; advantages of murine in vitro immunization; technical aspects of in vitro immunization of human B cells; and the advantages of human in vitro immunization and human monoclonal antibodies. Future developments likely to be made in this area of immunotechnology are outlined.