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Press Release from Research Diagnsotisc Inc

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Updated October 24, 1996

1D4: Monoclonal antibody specific for human plasma cells

-also see other tumor related antibodies for research with access to specs

Monoclonal antibodies with specificity for human plasma cells will have several applications, both in research and in the diagnosis and treatment of plasmacytoid malignancies (especially multiple myelomas). Monoclonal antibody CD38, which is widely used for detection of plasma cells by flow cytometry, although expressed on plasma cells, occurs on pre-B cells, immature T cells and activated T cells as well. In the literature, several monoclonal antibodies have been reported which react with plasma cells,e.g. PCA1, PCA2,PC1,R1-3,MM4 and HM1.24. However,these monoclonals appear to be not lineage-restricted either. CLB has developed 1D4, a novel plasma cell-specific monoclonal antibody, which is now available as a reagent.


Development of 1D4 antibody

We have been able to develop a new, unique human plasma cell-line (designated TH), from tissue of a patient with multiple myeloma1. The TH cell line has the typical morphological features of plasma cells, characterized by swollen,atypical endoplasmatic reticulum. In cytofluorometric analysis this cell line was shown to strongly express CD38. Apart from a weak and inconsistent expression of CD19, no other CD antigens could be demonstrated. TH cells showed a low intracellular expression of lambda light chains. TH-specific monoclonal antibodies were raised by conventional hybridoma techniques.

CAF-1 mice were immunized with TH cells and their spleen cells fused with SP2/0 myeloma cells. By means of immunoperoxidase staining in microtiter plates, antibody-forming cell clones were selected which reacted with TH cells, but not with cloned human T cells. In this way, clone 1D4 was obtained, which produces a plasma cell-specific monoclonal antibody of the IgG1 isotype 1.


Specificity of 1D4 antibody


By indirect immunofluorescence cytometry, antibody 1D4 was shown to react strongly with TH cells, with various plasmacytoma cell lines and with freshly isolated human plasma cells. The fluorescence pattern was distinctly membranous. Cells from all multiple myeloma cases tested stained positive. The antibody reacted moderately with EBV-transformed lymphoblastoid cell lines. No staining was observed with any other cells of lymphoid origin,including leukemic and normal B cells, although a weak reactivity was seen with acute lymphatic leukemia cells of B-lineage. When tested by an immunoperoxidase technique on cryostat sections of normal human organs (fresh surgical pathology specimens),no staining was observed on spleen,lymph nodes, thymus, arterial or venous endothelium, salivary gland, stomach, intestine,kidney, testis, brain,thyroid,uterus and ovary sections. Some reactivity was observed, however, on epithelial cells, in particular of skin and adnexes and with myoepitelium (especially of bronchi and pancreatic ducts).

When tested in cell culture, 1D4 did not affect the proliferation and immunoglobulin production of TH cells, nor of normal human B cells. 1D4 was shown to react with the same molecule as the monoclonal antibody BB4. 2) Recently, Wijdenes et al. 3) showed that BB4 recognizes syndecan 1, a trans-membrane heparin sulfate proteoglycan. Since we found that BB4 and 1D4 did not block each other, they are apparently directed against different epitopes. Antibody 1D4 was submitted to the forthcoming workshop on human leukocyte differentiation antigens (1996 CD Workshop).Together with antibodies MI15, B-B2 and B-B4, antibody 1D4 was indeed clustered by several-laboratories 4) as recognizing syndecan 1.


Ordering Information

Monoclonal antibody 1D4 (purified, each vial containing 0.2mg antibody) can be ordered from  Research Diagnostics INC using product number RDI- M1663clb  $375.00/vial . Labeling with different fluorochromes is in progress. All antibodies are strictly for in vitro research use only-not for use in or on human or animal-not for diagnostic purposes.


Reactivity of 1D4 on a continuous human plasma cell line. In the histogram (number of cells versus fluorescence intensity) the patterns obtained with 1D4 and with negative control antibody are superimposed. The strong,clear peak to the right corresponds with staining by 1D4 antibody. (Data kindly provided by Ludo Evers and Raymond Vet, Dept. of Hematology,Academic Medical Center, Amsterdam).


REFERENCES:


1. S.S. Weinreich et al.: Characterization of a human plasmacytoma line, British J. Haematol, 79 (1991) 226-234.

2. C.Clement et al,: B-B2 and B-B4, two new mAb against secreting plasma cells, in Leucocyte Typing V.Vol.1 (S.F.Schlossman et al.ed.), Oxford University Press 1995, pp.714-715.

3. Wijdenes et al,: A plasmocyte selective monoclonal antibody (B-B4) recognizes syndecan-1, British J. Haematol, 94 (1996) 318-323.

4. M Jones and D.Y. Mason, personal communication.


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