Role of the Neonatal Fc Receptor for IgG in the Pathophysiology of Lupus

Study Overview
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Brief Summary
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This study evaluates the expression of the neonatal fc receptor (FcRn) in white blood cells and antigen-presenting cells (APC) in active lupus patients compared to inactive lupus patients and control to investigate if it's upregulated or not.

Detailed Description
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FcRn is an intracellular receptor which binds the Fc of immunoglobulins G (IgG) and albumin which induce an upgraded half-life of this two proteins. It's extended role involve the regulation of immune complexes and anti-tumoral immunity, some studies showing a direct correlation between it's expression and the tumor surface and prognosis. Recently a role in the upregulation of humoral response with a increase of the antibodies's diversity and a more efficient priming of lymphocyte B have been evocated. The lupus erythematosus is an auto-immune disease mediated by IgG and immune complexes characterized by a high diversity of autoantibodies and a large dysregulation of the immune system in all it's components. In this study, by analogy with the founding in anti-tumoral immunity, the investigators hypothesised that in an active lupus disease the expression of FcRn is upregulated in the white blood cells and in APC. This is followed by an extended half life of IgG autoantibodies and immune complexes inducing direct damages by their deposit in tissues and indirectly by upregulating the humoral response, leading to anormal production of a large panel of autoantibodies.

Official Title
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Role of the Neonatal Fc Receptor for IgG in the Pathophysiology of Lupus

Conditions
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Lupus Erythematosus, Systemic

Intervention / Treatment
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* Other: Blood samples


Participation Criteria
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Eligibility Criteria
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Inclusion criteria: Lupus erythematosus newly diagnosed or active Inactive lupus erythematosus Needing a blood sample for diagnosis or follow up Signed informed consent Exclusion criteria: Other auto immune disease Pregnant or brest feeding Legal protection or protected adults

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Lupus erythematosus<br>Patients with inactive lupus erythematosus, active lupus erythematosus or newly diagnosed | Other: Blood samples<br>* Blood samples<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Expression of FcRn in active or newly diagnosed lupus erythematosus compared with inactive lupus erythematosus | Measurement in flow cytometry of the fluorescence's mean of FcRn in each type of white blood cells | At baseline | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| FcRn genotyping (FCGRT) | FcRn gene polymorphism analysis (FCGRT) | At baseline | 
| IGHG1 genotyping | IGHG1 gene polymorphism analysis | At baseline | 
| Expression of FcRn in CD16 monocytes | CD16 is used to differentiate subpopulation of monocytes. The investigators will evaluate the correlation between expression of CD16 and the fluorescence's mean of FcRn measured in flowcytometry. This measure will be done for each population of participants | At baseline | 
| Expression of FcRn in macrophages | After a positive selection of monocytes obtained from participants, the investigators will measure the fluorescence's mean of FcRn in this cells for each population of participants | At baseline |