1. IgM Autoantibodies to Complement Factor H in Atypical Hemolytic Uremic Syndrome
- Author
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Donata Cresseri, Massimo Cugno, Silvana Tedeschi, Piergiorgio Messa, Sara Testa, Gianluigi Ardissino, Elena Grovetti, Sonia Caccia, Silvia Berra, Federica Depetri, Samantha Griffini, Flora Peyvandi, and Fabio Giglio
- Subjects
Adult ,Male ,Bone marrow transplant ,Thrombotic microangiopathy ,Adolescent ,Young Adult ,Clinical Research ,Atypical hemolytic uremic syndrome ,Humans ,Medicine ,In patient ,Child ,Atypical Hemolytic Uremic Syndrome ,Autoantibodies ,business.industry ,Autoantibody ,General Medicine ,Middle Aged ,medicine.disease ,medicine.anatomical_structure ,Immunoglobulin M ,Nephrology ,Case-Control Studies ,Child, Preschool ,Complement Factor H ,Factor H ,Immunology ,Female ,Bone marrow ,business - Abstract
Background Atypical hemolytic uremic syndrome (aHUS), a severe thrombotic microangiopathy, is often related to complement dysregulation, but the pathomechanisms remain unknown in at least 30% of patients. Researchers have described autoantibodies to complement factor H of the IgG class in 10% of patients with aHUS but have not reported anti-factor H autoantibodies of the IgM class. Methods In 186 patients with thrombotic microangiopathy clinically presented as aHUS, we searched for anti-factor H autoantibodies of the IgM class and those of the IgG and IgA classes. We used immunochromatography to purify anti-factor H IgM autoantibodies and immunoenzymatic methods and a competition assay with mapping mAbs to characterize interaction with the target protein. Results We detected anti-factor H autoantibodies of the IgM class in seven of 186 (3.8%) patients with thrombotic microangiopathy presented as aHUS. No association was observed between anti-factor H IgM and homozygous deletions involving CFHR3-CFHR1. A significantly higher proportion of patients with bone marrow transplant-related thrombotic microangiopathy had anti-factor H IgM autoantibodies versus other patients with aHUS: three of 20 (15%) versus four of 166 (2.4%), respectively. The identified IgM autoantibodies recognize the SCR domain 19 of factor H molecule in all patients and interact with the factor H molecule, inhibiting its binding to C3b. Conclusions Detectable autoantibodies to factor H of the IgM class may be present in patients with aHUS, and their frequency is six-fold higher in thrombotic microangiopathy forms associated with bone marrow transplant. The autoantibody interaction with factor H's active site may support an autoimmune mechanism in some cases previously considered to be of unknown origin.
- Published
- 2021
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