A human monoclonal antibody against HLA-A25

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.

Nucleotide sequences of the variable regions of a human monoclonal antibody against HLA-A1, A23, and A24

Nucleotide sequences of the heavy and light chain variable (VH and VL) regions of a human monoclonal antibody (4-35-7), which recognized HLA-A1, A23 and A24, were determined by means of the reverse transcriptase-polymerase chain reaction. This antibody was generated by Epstein-Barr virus transformation of lymphocytes obtained from a multiparous donor, followed by fusion with mouse myeloma cells. The VH gene segment belonged to the VHIII gene family, and used the DXP4 and JH4 gene segments. This VH gene segment had 92.9% homology to the germline gene VH26, and contained 21 nucleotide substitutions. Fourteen of them generated the replacements of amino acids, while 7 failed to generate the replacement. The ratio of replacement to silent mutations in complementarity determining regions (CDRs) was 7.0. The VL gene segment belonged to the VkI gene family, and used Jk4. This VL gene segment showed 96.1% homology to the germline gene HK102, and contained 11 nucleotide substitutions. Seven of them generated the replacement of amino acids, while 4 failed to generate the replacement. The high ratio of replacement to silent mutations in CDRs of the VH gene segment suggested that the multiparity caused the processes of antigenic selection and somatic mutation, and generated this anti-HLA antibody.

A human monoclonal antibody that detects HLA-A1, A23 and A24 antigens

We report the production and characterization of a human monoclonal IgM (mu, kappa) antibody recognizing the HLA A1, A23 and A24 antigens. B lymphocytes obtained from a multiparous Japanese woman were transformed in vitro by Epstein-Barr virus, screened with an immune adherence assay, and fused with a murine myeloma cell line, P3-X63-Ag8.653. After subcloning by limiting dilution three times, a stable antibody-secreting hybridoma cell line, 4-35-7, was identified. The culture supernant had a titer of 1:32-64 against each of A1-, A23- and A24-positive lymphocyte panels, and showed complete correlation (r = 1.00) with the A1, A23 and A24 antigens on a lymphocyte panel of 287 unrelated, class I HLA-typed donors by the NIH cytotoxicity assay. Monoclonality of the antibody was ensured by Southern blot analysis of the human immunoglobulin heavy chain gene of 4-35-7. In view of the published data on HLA class I nucleotide sequences, the antibody may recognize an antigeneic determinant including two amino acid residues, Asp-166 and Gly-167, in the alpha 2 helix of the class I molecule that are specific for A1, A23 and A24 so far analyzed.

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.

Production of two human hybridomas secreting antibodies to HLA-DRw11 and--DRw8+w12 specificities

In this study we describe the production of two human monoclonal antibodies (mAbs) HMP12 and HMP14, that recognize polymorphic HLA-DR specificities. These mAbs have been produced by hybridization of antibody-secreting Epstein-Barr virus-transformed cells with SHM-D33 human-mouse heteromyeloma. By microcytotoxicity assay HMP12 mAb was found to react with all DRw11-positive cells and HMP14 mAb with all cells bearing the DRw8 or the DRw12 specificity. Cytotoxic activity of HMP14 was completely removed after absorption with DRw8- or DRw12-positive cells and unaffected by absorption with cells carrying different DR specificities. The HLA specificity was further analyzed by cytofluorometry on mouse transfectant cells. The reactivity of the two mAbs was correlated with the presence of a particular polymorphic amino acid residue in the DR beta chain and by this approach the epitopes possibly involved in the antibody binding sites were predicted.

Generation of a human hybridoma producing a pure anti-HLA-A2 monoclonal antibody

We report the production and characterization of a human monoclonal IgM hybridoma antibody recognizing antigen HLA-A2. B lymphocytes obtained from the peripheral blood of a multiparous volunteer 1 week postpartum were transformed in vitro by Epstein-Barr virus, screened by a microlymphocytotoxicity assay, and electrofused with the heterohybridoma fusion partner, K6H6/B5. A specifically anti-A2 secreting hybridoma cell line. MBW1, was then identified and cloned. The cytotoxic IgM antibody produced showed complete correlation (r = 1.00) with the A2 antigen on a large panel of unrelated donors' lymphocytes, and no cross-reactivity with A28, Aw68, or Aw69 antigens was observed.

Production of a cytotoxic human monoclonal antibody with specificity for HLA-DR4 and -DRw10 by cells derived from a highly sensitized kidney recipient

A human monoclonal antibody which reacts preferentially with HLA-DR4 and -DRw10 B-cell targets has been produced. A human B-cell line, secreting antibody which reacted preferentially with DR4 and DR1 targets, was derived from a highly sensitized kidney recipient who had rejected two grafts. This line was fused with the mouse myeloma P3X63Ag8.653 and a selected hybridoma cloned. The clones secrete IgM(lambda), which reacts strongly with HLA-DR4 and -DRw10 and more weakly with -DRw14 and a proportion of -DR1 B cells in cytotoxicity assays. Using B-cell lines as targets in cytotoxicity and enzyme-linked immunosorbent assays, the antibody gives a broader pattern of reaction, reacting with HLA-DR1, -DR4, -DR9, -DRw10, -DRw14, and some -DR2 targets. The antibody (NI) is currently in use as a reagent for tissue typing.

Two cytotoxic human-human hybridoma antibodies to HLA: TrAH10 (anti A3.1) and TrAG2 (anti B7, Bw42)

Two cytotoxic human-human hybridoma IgM antibodies to HLA were generated by EBV transformation of PBMC from multiparous women and fusion of EBV transformed cells with the human fusion partners KR4 or KR12. Both mAbs required the sensitive immunomagnetic cytotoxicity method to display killing of freshly prepared PBMC. One mAb (TrAH10) was specific for HLA-A3. Strikingly, TrAH10 reacted much more strongly with lymphoblastoid cell lines of HLA-A3.1 than of the rare variant HLA-A3.2, previously detected by cytotoxic T cells. Thus, in the microcytotoxicity test, the titer of concentrated TrAH10 was approximately 2000 times higher for A3.1 as compared to A3.2, and a clear difference was also observed in radioimmunoassay. Since the two HLA-A3 variants differ by only two amino acids at positions 152 and 156 of the alpha 2-domain's alpha-helix, the epitopes defined by the mAb TrAH10 and HLA-A3.1 specific cytotoxic T cells must be closely related. The observations with TrAH10 suggest that the HLA polymorphism detected by human mAbs may turn out to be as extensive as the T-cell defined HLA polymorphism. The other mAb (TrAG2) bound B7 and Bw42 with equal strength, and in addition bound weakly to some cells that were Bw22 or B39. Magnetic polymerbeads coated with affinity purified human mAbs TrAH10 or TrAG2 formed rosettes with EBV transformed cells carrying relevant HLA antigens; however, rosette formation with freshly isolated PBMC was very weak and unsuitable as a typing assay.

Production of monoclonal human antibody to HLA-DR5 (DRw11) by mouse/human heterohybridomas

We describe here the production of a human monoclonal antibody to the HLA-DR5 antigen. A human B-cell line secreting cytotoxic antibody that reacted preferentially with DR5-positive targets was fused to the mouse myeloma P3X63Ag8.653 and the resulting heterohybridomas cloned twice. The clones secreted human IgM (lambda light chain), which showed specificity for the DR5 antigen in cytotoxicity assays and reacted with DRw11-positive but not DRw12-positive targets. These results demonstrate the potential of this approach to the production of human monoclonal antibodies to transplantation antigens.

A supertypic HLA class II determinant shared by DR1 and DRw9, and crossreactive with DR2, defined by human monoclonal antibody

A human monoclonal antibody Pez.2F5, produced by a lymphoblastoid cell line, has been established in vitro by Epstein-Barr virus (EBV) transformation of B lymphocytes isolated from the blood of a volunteer immunized with allogeneic peripheral blood leukocytes (PBLs). The antibody reacted with a new supertypic determinant expressed on all lymphoblastoid cell lines homozygous for HLA-DR1, -2, and -w9. The genetic linkage of the Pez.2F5 determinant to the HLA region was demonstrated by family segregation studies. Quantitative absorption studies indicated that DR2-positive cells required more Pez.2F5 antibody for lysis, and since their absorption capacity was significantly lower than that of DR1- or DRw9-positive cells, it is likely that the Pez.2F5 determinant of the DR2 haplotype is crossreactive but not identical with the determinant found on the latter haplotypes. In addition, on a test panel of HLA-typed B lymphocytes, Pez.2F5 showed perfect correlation with DR1 and DRw9, but reacted with only a fraction of DR2-positive cells. The Pez.2F5 determinant was found to be absent from resting T lymphocytes, but its expression could be identified on IL-2-dependent T-cell lines by cytotoxicity and flow cytofluorometric analysis. By sequential immunoprecipitation and SDS gel analysis of antigens of DR1 cells it was determined that the Pez.2F5 determinant is carried by HLA class II DR molecules. Thus, the Pez.2F5 is the first described human monoclonal antibody able to immunoprecipitate HLA class II-related molecules.