Acute autoimmune hemolytic anemia due to a low molecular weight IgM cold hemolysin associated with episodic lymphoid granulomatous vasculitis

A case study of a child with chronic hemolytic anemia due to a Donath-Landsteiner positive, IgM anti-I autoantibody

In children, paroxysmal cold hemoglobinuria (PCH) is generally considered an acute self-limited autoimmune hemolytic anemia caused by an IgG biphasic auto-anti-P antibody identified by the Donath-Landsteiner (D-L) test. We report a case of a 5-year-old female with a chronic hemolytic anemia. The etiology of the hemolysis appears to be an unusual D-L positive, IgM antibody with specificity for the I antigen. The clinical course is described and a discussion of PCH and the D-L antibody is presented. We also discuss intravenous immunoglobulin infusions as a therapy for children with this form of severe chronic autoimmune hemolytic anemia.

Detection of IgM autoantibodies in eluates from red blood cells

Forty-two patients with autoimmune haemolysis, whose red cells were sensitized with IgM, were studied in order to determine suitable techniques for investigating the form of erythrocyte-bound IgM, particular emphasis being placed on identifying forms of low molecular weight. Four elution techniques were assessed for their efficiency in removing cell-bound IgM; these were the heat elution, acid stromal, organic solvent and freeze-thaw methods. Eluted IgM was detected by polyacrylamide gel electrophoresis followed by immunoblotting; the heat elution method proved to be the best. Although oligomeric forms of IgM were found in 64% of patients' sera tested concurrently, only pentameric IgM was eluted; from this it was concluded that low molecular weight IgM was not causing haemolysis in any of the cases studied but that the methods would readily detect its presence.

IgM monomers accelerate disease manifestations in autoimmune-prone Fas-deficient mice

The monomeric form of IgM, also known as low molecular weight IgM, is found in increased concentrations in patients chronically infected with a variety of viral and bacterial pathogens or suffering from various autoimmune diseases. Whether monomeric IgM contributes to the disease process, however, is not known. To address this question, transgenic mice were created that secreted elevated levels of IgM monomers. In normal mice (C57BL/6), the presence of IgM monomers did not alter the composition of the immune system significantly: lymphocyte subsets and serum antibody levels were normal, with the exception of increased levels of IgM due to the presence of the monomers. Immune responses also appeared to be normal. Transgenic mice did develop antinuclear antibodies (ANA) earlier than non-transgenic littermates, but did not develop further indications of autoimmune disease. When the transgene was expressed in the autoimmune-prone strain of mice, B6.MRL-Tnfrsf6(lpr) (B6/lpr), these mice developed autoimmune manifestations more rapidly than non-transgenic littermates, including hypergammaglobulinemia, splenomegaly, and ANA production. Transgenic mice also displayed earlier evidence of immune complex deposition in the kidneys. From these results, we conclude that monomeric IgM does not induce autoimmune disease, but its presence can accelerate the onset of autoimmune manifestations in otherwise autoimmune prone animals.

Monomeric (7S) IgM found in the serum of rheumatoid arthritis patients share idiotypes with pentameric (19S) monoclonal rheumatoid factors

Serum from some seropositive (RF+) rheumatoid arthritis (RA) patients contains relatively high concentrations of monomeric (7S) IgM molecules. Seven S IgM molecules fail to bind the Fc portion of IgG, unlike 19S IgM RFs that bind aggregated IgG in classical RF assays. Some pentameric IgM RFs are marked by crossreactive idiotypes (RCRI) defined by prototypic monoclonal RFs. In previous studies, we observed that a proportion of pokeweed mitogen (PWM) induced plasma cells from RA patients' blood lymphocytes express the major RCRI as assayed by indirect immunofluorescence with polyclonal anti-RCRI antibodies. In this study, 7S IgM obtained from three different RF+ RA patients inhibits specific anti-RCRI intracytoplasmic staining of PWM induced RF+ RA-derived plasma cells. These 7S molecules also block polyclonal anti-RCRI antibodies from reacting with red blood cells bearing 7S IgM molecules from RF+ patients with RA or Waldenstrom's macroglobulinemia. We conclude that some 7S IgM molecules in the serum of RF+ RA patients are marked by the major RCRI idiotype and are related to 19S monoclonal and polyclonal RFs.

Erythrocyte sensitization with monomeric IgM in a patient with hemolytic anemia

An automated antiglobulin test showed that erythrocytes of a patient with an acute episode of Coombs-negative hemolytic anemia were strongly sensitized with nonagglutinating IgM molecules. The bound antibodies, after elution from red blood cell stroma, were found to be monomeric IgM, since they migrated with IgG molecules on an agarose column, although they were proved to be immunoglobulin M, not G, by a sensitive hemagglutination inhibition assay. The hemolysis subsided with steroid therapy, but ANA increased to a titer greater than 1,024 (with peripheral pattern) without other laboratory evidence of systemic lupus erythematosus. In addition, the patient demonstrated photosensitivity and nonscarring alopecia. We consider that this appearance of erythrocyte autoantibodies consisting of monomeric IgM was a symptom of atypical SLE.