Mouse Myeloma Proteins

Myeloma is a cancer of the antibody-producing plasma cells. It occurs spontaneously in humans and mice, and can be induced by injecting some substances such as mineral oil, pristane, or viruses into the peritoneum. Myeloma cells continue to secrete immunoglobulins in a normal fashion, but exhibit uncontrolled growth. As the number of myeloma cells increases, the level of myeloma immunoglobulins in plasma also rises, eventually inhibiting the production of immunoglobulin by normal plasma cells.
Plasmacytomas have been cloned from myelomas, yielding cell lines that produce a completely homogeneous population of myeloma immunoglobulin bearing a single heavy chain isotype and a single light chain type. This myeloma protein retains the antigen specificity of the Ig produced by the plasma cell from which the myeloma originated, although that specificity is not usually known. Plasmacytomas may be propagated as tumors in the peritoneum of animals, secreting myeloma Ig into the surrounding ascites fluid, or in cell culture, secreting myeloma Ig into the culture supernatant. Mouse plasmacytomas bear designations consisting of an alphabetic prefix, an accession number, and sometimes a letter to indicate a subclone. The prefix is usually derived from the tumorigenic agent or the last initial of the investigator who induced the tumor, sometimes combined with PC for plasmacytoma.1 The table below lists some prefixes used for the myelomas offered by Sigma, along with their meaning:
MO = Mineral oil (such as MOPC)
HO = 7-n-Hexyloctadecane (such as HOPC)
TE = Tetramethylpentadecane (pristane) (such as TEPC)
Y = Yancy
AB = Abelson virus (such as ABPC)
Mouse myeloma proteins are produced by plasmacytoma lines carried intraperitoneally in BALB/c mice. Ascites fluid produced by the mice contains elevated levels of the myeloma protein produced by the plasmacytoma, as well as normal immunoglobulins and other serum proteins. Sigma offers mouse myeloma proteins as clarified ascites or purified immunoglobulins. Each purified myeloma immunoglobulin represents a single subclass and light chain type.
Note: The light chain designation following the subclass refers to the type of light chain carried on the immunoglobulin molecule.
Mouse myeloma proteins have many applications:
1. Due to the homogeneity of these immunoglobulins, they are useful for amino acid sequencing studies.2
2. They may serve as positive isotype controls in the characterization of monoclonal antibodies and as negative controls for monoclonal antibodies in immunoassays.3 When using mouse myeloma proteins as negative controls, it is important to match not only the immunoglobulin isotype but also the level of purity and the immunoglobulin concentration as closely as possible. For instance, if the test monoclonal is in ascites, then a clarified ascites product should be used for the negative control. If the monoclonal has been purified, then the purified myeloma immunoglobulin is a better choice. In either case, the concentration of the myeloma protein should be adjusted to approximate the concentration of the test monoclonal antibody. When testing monoclonal antibodies in cell culture supernatant, use the purified myeloma protein diluted in cell culture medium to the approximate concentration of the test monoclonal antibody.
3. Where the antigen specificity is known, mouse myeloma proteins may be used as capture antibodies in capture ELISA or as primary antibodies in immunohistochemistry or immunocytochemistry for targets bearing that antigen.
4. Myeloma IgG and IgM may be used as molecular weight markers.
1. Potter, M., Immunoglobulin-producing tumors and myeloma proteins of mice. Physiol. Rev., 52, 631-719 (1972).
2. Kehry, M. et al, Amino acid sequence of a mouse immunoglobulin μ chain., Proc. Nat. Acad. Sci. USA, 76, 2932-2936 (1979).
3. Kramer, K. et al., Prognostic value of TrkA protein detection by monoclonal antibody 5C3 in neuroblastoma. Clin. Cancer Res., 2, 1361-1367 (1996).