Skip to main content

Frequency and role of low molecular weight IgM in systemic lupus erythematosus

Study of patients from different ethnic origins


Low molecular weight IgM (LMW IgM) is the monomeric subunit of the naturally occurring pentameric IgM. It is not seen in health but has been previously observed in systemic lupus erythematosus (SLE) particularly in those patients with active disease and may reflect an adverse prognostic finding. We have therefore studied the presence of LMW IgM in 33 Chinese or Malay SLE patients (Singapore) and 21 Caucasian patients (Adelaide). LMW IgM was measured using filtration chromatography or by a sensitive immunoblotting technique. LMW IgM was observed in all patients in the Adelaide group and in 32 patients in the Singapore group with slightly greater quantities being seen in the Adelaide group. LMW IgM constituted up to 15.3% of the total IgM and was frequently associated with the presence of other low molecular weight IgM oligomers. In both groups LMW IgM correlated significantly with the total IgM levels (P<0.01). In a more detailed study in the Singapore group LMW IgM also correlated significantly with the IgM anticardiolipin levels (P=0.02) but not with IgG anticardiolipin or with IgG or IgM anti-DNA levels or with rheumatoid factor. Patients with more extensive organ involvement had higher levels of LMW IgM but not at a significant level. We conclude that circulating LMW IgM occurs almost universally in SLE, is closely related to the total IgM levels and appears independent of ethnic background. The significance of LMW IgM in this disorder is unclear.

This is a preview of subscription content, access via your institution.


  1. Bush ST, Swedlund HA, Gleich GG (1969) Low molecular weight IgM in human sera. J Lab Clin Med 73: 194–201

    PubMed  Google Scholar 

  2. Dammacco F, Guistavo V, Bonomo L (1970) The occurrence of serum 7S IgM in disease associated with immunoglobulin abnormalities. Int Arch Allergy 38: 618–626

    PubMed  Google Scholar 

  3. Roberts-Thomson PJ, Wernick RM, Ziff M (1981) Low molecular weight IgM in rheumatoid arthritis and other rheumatic diseases. Arthritis Rheum 24: 795–802

    PubMed  Google Scholar 

  4. Jones DN, Koh LY, Bertouch JV, Roberts-Thomson PJ (1985) Synthesis of low molecular weight IgM in vitro in rheumatoid arthritis. Arthritis Rheum 28: 112–118

    PubMed  Google Scholar 

  5. Harris-Dangkul VH, McDougal JS, Knapp M, Christian CL (1975) Naturally occurring low molecular weight IgM in patients with rheumatoid arthritis, systemic lupus erythematosus and macroglobulinaemia: purification and immunological studies. J Immunol 115: 216–222

    PubMed  Google Scholar 

  6. Harris-Dangkul VH, Barnes TY, Songcharoen S, Pennebaker JB (1984) Clinical significance of low molecular weight IgM in patients with systemic lupus erythematosus. J Rheumatol 11: 638–643

    PubMed  Google Scholar 

  7. Roberts-Thomson PJ, Neoh SH, Bradley J (1980) Quantitation and evaluation of low molecular weight IgM in rheumatoid arthritis. Ann Rheum Dis 39: 349–353

    PubMed  Google Scholar 

  8. Harris R, Beckman I, Roberts-Thomson PJ (1986) Low molecular weight IgM: detection using immunoblotting. J Immunol Methods 88: 97–100

    Article  PubMed  Google Scholar 

  9. Sutjita M, Hohmann A, Boey ML, Bradley J (1989) Microplate ELISA for detection of antibodies to DNA in patients with systemic lupus erythematosus: Specificity and correlation with Farr radioimmunoassay. J Clin Lab Analysis 3: 34–40

    Google Scholar 

  10. Virella G, Fudenberg HH (1977) Comparison of immunoglobulin determinations in pathological sera by radial immunodiffusion and laser nephelometry. Clin Chem 23: 1925–1928

    PubMed  Google Scholar 

  11. Rothfield NF, Frangione B, Franklin EC (1965) Slowly sedimenting mercaptoethanol-resistant antinuclear factors related antigenically to M immunoglobulins in patients with systemic lupus erythematosus. J Clin Invest 44: 62–72

    PubMed  Google Scholar 

  12. Saiki O, Saeki Y, Tanaka T, Doi S, Hara H, Negoro S, Igarashi T, Kishimoto S (1987) Development of selective IgM deficiency in systemic lupus erythematosus patients with disease of long duration. Arthritis Rheum 30: 1289–1292

    PubMed  Google Scholar 

  13. Hughes TP, Jones P, Rozenberg MC (1989) Hypergamma-globulinemia and the anticardiolipin antibody test (letter). Arthritis Rheum 32: 813

    Google Scholar 

  14. Roth RA, Koshland ME (1981) Identification of a lymphocyte enzyme that catalyzes pentamer immunoglobulin M assembly. J Biol Chem 256: 4633–4639

    PubMed  Google Scholar 

  15. Davis AC, Shulman MJ (1989) IgM molecular requirements for its assembly and function. Immunol Today 10: 118–128

    Article  PubMed  Google Scholar 

  16. Roberts-Thomson PJ, Shepherd K, Southwood TR, Ahern MJ, Koh LY, O'Donnell J, Ziegler J, Edmonds J (1988) Low molecular weight IgM in juvenile chronic arthritis. Arch Dis Child 63: 1453–1456

    PubMed  Google Scholar 

Download references

Author information

Authors and Affiliations


Rights and permissions

Reprints and Permissions

About this article

Cite this article

Roberts-Thomson, P.J., Shepherd, K., Bradley, J. et al. Frequency and role of low molecular weight IgM in systemic lupus erythematosus. Rheumatol Int 10, 95–98 (1990).

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI:

Key words

  • IgM
  • Systemic lupus erythematosus
  • Ethnic background