Human antibodies and hybridomas最新文献

In vitro immunization of human B-lymphocytes was performed with liposomes containing the monosialoganglioside GM3, with or without either complete tetanus toxoid or a synthetic T helper epitope derived from tetanus toxin (determinant 830-843). The immunized B-cells were Epstein-Barr virus transformed and the human anti-ganglioside antibody response was evaluated using an indirect ELISA against different mono- and disialogangliosides. Clones producing antigen-specific human antibodies of the IgM isotype against the ganglioside GM3 used as the immunogen were selected and one clone, IM-11, was further characterized. In addition, a method of positive selection using GM3-coated magnetic beads has been developed which allowed us to rescue unstable clones. The binding of the human antibody IM-11 to a large panel of glycosphingolipids separated on thin-layer plates was studied. The human MAb IM-11 was found to bind strongly to NeuAcGM3, IV3 NeuAcnLc4 and sulfate containing glycosphingolipids and weakly to NeuGcGM3. Immunohistological staining of melanoma and breast cancer biopsy sections showed a selective reactivity of IM-11 with tumor cells which varied among different tumors.

SP2/0Ag14 murine myeloma cells transfected with the expression vector mpSV2neo-EP-FV-CH2-3-PA containing the single gene FV-CH2-3 secreted a single-gene-encoded chimeric antibody molecule FV/M4. This single-chain protein consisted of the heavy- and light-chain variable (VH and VL) domains covalently joined through a flexible linker peptide, while the carboxyl end of VL domain was connected to the amino terminus of hinge region of the ccM4 heavy-chain. Our data showed that the FV/M4 retained both its immunoreactivity for tumor-associated TAG72 antigen and its cytolytic activity to tumor cells as did the parental ccM4 antibody. Therefore, this single-gene-construct approach circumvents inefficiencies inherent in delivering two genes into a mammalian cell for assembly of a functional chimeric antibody and provides an alternative for construction of chimeric antibodies. It is particularly attractive for ex vivo transfection of cells from patients for certain gene-therapy modalities not only for cancer but also for a range of diseases in which immunotherapeutic approaches are used.

In this study, B-cells isolated from rheumatoid synovial tissue were immortalized, without prior in vitro stimulation, by means of electric-field induced fusion and conventional PEG fusion in order to compare the efficiency of these methods. Two myeloma cell lines were used as fusion partners, the murine myeloma Ag8 and the murine-human heteromyeloma HAB-1. The results of seven fusion experiments performed simultaneously with identical cell populations showed that fusion frequencies obtained by electrofusion were 4 to 35 times higher than by the PEG fusion technique. The morphological and immunohistochemical evaluation of synovial tissues used for fusion showed that only tissues exhibiting a follicular distribution of B-cells with a high percentage of CD 22-positive lymphocytes gave rise to high fusion yields and produced B-cell clones, whereas synovial tissues with the same percentage of plasma cells but lower percentages of CD 22 lymphocytes yielded very low fusion rates. In conclusion, electrofusion is more efficient for immortalizing small amounts of synovial tissue B-lymphocytes than PEG fusion, since high fusion frequencies could be obtained by this technique without the need for prior in vitro stimulation. Synovial tissue exhibiting a follicular distribution of B-lymphocytes with high percentages of CD 22-positive lymphocytes gave rise to high hybridoma yields and therefore an ideal source of human rheumatoid B-cell clones.

The VH4-21 (V4-34) gene segment, a member of the VH4 family, is expressed early in B-cell maturation and is utilized by approximately 6% of normal adult B lymphocytes. This prevalence indicates an importance of VH4-21 in the B-cell repertoire. The gene also encodes certain autoantibodies being mandatory for pathological IgM anti-red cell antibodies directed against the I/i antigen, and also capable of encoding anti-DNA antibodies. Recognition of I/i antigen or DNA appears to be via two distinct sites on VH, with I/i binding mediated by sequences in the framework region, and DNA binding correlating with the presence of positively charged amino acids in complementarity-determining region 3. However, these positively charged residues appear to suppress the ability of the framework region to interact with I/i, rendering a single sequence monospecific for I/i or DNA. The IgM anti-DNA antibodies also recognize bacterial lipid A, whereas the anti-I/i antibodies do not, indicating that CDR3 may be involved in binding the negatively charged lipid A. Structural similarities between the DNA backbone and lipid A provide a possible explanation for this cross-reactivity. This dual recognition of bacterial antigen and autoantigen provides a potential link between infection and autoimmunity.