Human-human hybrids secreting pneumococcal antibodies

Optimizing production of human monoclonal IgG antibodies by in vitro-primed human PBMC: influence of CD56+ NK cell depletion

Freshly isolated human peripheral blood mononuclear cells (PBMC) were immunomagnetically depleted of CD56+ cells. When these CD56- PBMC populations were cultured in the presence of autologous donor serum, polyclonal activation with IL-2 and pokeweed mitogen (PWM) generally resulted in exclusive production of IgG antibodies. Fusion with SP2/O-Ag14 mouse myeloma cells was highly efficient and yielded a great number of IgG-producing heterohybridomas. These conditions were used for in vitro immunization with viable human HT29 tumor cells. After fusion, an increase in hybridoma clones producing IgG monoclonal antibodies (MAb) with HT29 specificity showing a higher portion of MAb binding to the surface of viable HT29 cells was recorded. This immunizing efficiency was not observed with HT29 membrane protein fractions or HT29 proteins integrated into ISCOM particles. Investigations with human anti-alpha Gal antibodies showed that the IgG antibodies produced by the human/mouse heterohybridomas did not contain the mouse-specific Gal alpha 1-3Gal epitope.

Germ line transcription of the immunoglobulin heavy chain locus directs production of mu chain without VDJ

Immunoglobulin VDJ recombination is associated with transcriptional activation of the Ig variable region elements. We have previously described a novel Ig mu chain protein and mRNA produced by pre-B cell hybrids from normal and X-linked agammaglobulinemic bone marrow. We have now characterized the mRNA encoding this protein and find that it is composed of a 5' leader sequence spliced to C mu (LS-C mu), lacking the variable (V), diversity (D), and joining (J) gene sequences. The leader sequence is encoded by a novel exon 16 kb upstream of the JH locus. Transcription of the germ line heavy chain locus from this LS exon results in transcriptional activation of the JH locus, apparently the initial step in commitment to B lymphoid development. Polymerase chain reaction amplification of normal bone marrow shows that these germ line LS-C mu transcripts are a product of bone marrow pre-B cells. Production of LS-C mu commences a sequential process of transcriptional activation, with concordant translation of Ig rearrangement intermediates, in the process of creating a productive VDJ rearrangement.

The production and application of non-rodent monoclonal antibodies in veterinary science

The requirement for monoclonal antibodies derived from species other than rats and mice is becoming increasingly realised in veterinary, as well as human, medicine. This paper reviews current knowledge of the production of inter-species hybridomas (heterohybridomas) by the fusion of rodent myeloma cell lines with lymphocytes from species of veterinary importance. To date a number of monoclonal immunoglobulins derived from sheep, cattle, pig, rabbit, mink and primate species have been produced to a variety of different bacterial, viral and nematode pathogens as well as to blood group and MHC determinants and to hormones. The technique opens up a number of possibilities for the future; some of these applications are discussed in relation to the antibodies produced thus far.

Correction of the molecular defect in B lymphocytes from X-linked agammaglobulinemia by cell fusion

The X chromosome-linked antibody deficiency disease, X-linked agammaglobulinemia (XLA), results from failure of B lymphoid development. In the minor form of XLA, B lymphoid development terminates at the stage of immature B lymphocytes that produce truncated Ig heavy (H) chains composed of D-J-C(mu/delta), resulting from failure of VH gene rearrangement. Fusion of B cells from a patient with the minor form of XLA with mouse myeloma results in complementation of this defect; hybrid cells produce full-length H chains composed of VH-D-JH-C. The VH gene is of human origin. Complementation occurs independent of retention or loss of the human X (XLA) chromosome in the hybrid cells. These results indicate that the D-JH-C structure of the XLA B cells is fully functional for the subsequent rearrangement of a VH gene element, and that failure of immunoglobulin expression is susceptible to correction.

The construction and use of a human-mouse myeloma analogue suitable for the routine production of hybridomas secreting human monoclonal antibodies

A human-mouse myeloma analogue termed HMMA2.11TG/O was constructed by fusion of the mouse myeloma cell line P3x63Ag8.653, a mutant derivative of MOPC21, with bone marrow mononuclear cells from a patients with IgA myeloma. The HMMA2.11TG/O cell line is resistant to 6-thioguanine and ouabain and sensitive to HAT. The cell line secretes no detectable immunoglobulin and has a hybrid karyotype and cell surface phenotype. An average fusion efficiency for growth of hybridomas of 1/17,000 fused cells was obtained in fusions with human peripheral blood mononuclear cells (PBM), Pokeweed Mitogen (PWM) stimulated PBM, and Epstein-Barr Virus (EBV) transformed polyclonal B cell lines. Over 75% of hybrids secrete detectable immunoglobulin and the cloning efficiency of the hybrids at 1 cell/well averages 25%. Antibody secreting cloned hybridoma cell lines were obtained by fusion directly with PBM from an immunized volunteer and by fusion with in vitro, secondarily immunized, EBV transformed polyclonal cell lines. Five hybridomas secreting human monoclonal IgM anti-tetanus antibodies and 2 secreting human monoclonal IgG anti-tetanus antibodies were selected and cloned from 6 fusions performed specifically for anti-tetanus antibody. Immunoglobulin and antibody secretion by cloned hybrids has been stable for 5-10 months at present. Immunoglobulin and antibody secretion in routine cultures passaged every 3-4 days has been 8-42 micrograms/ml. This human-mouse myeloma analogue should prove useful for the routine production of human monoclonal antibodies.