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Differences in HLA antigens between patients with mixed connective tissue disease and systemic lupus erythematosus
P Ruuska1, R Hämeenkorpi, S Forsberg
1Department of Medical Microbiology, University of Oulu, Finland.
Insights
Human leukocyte antigen (HLA) associations differ between mixed connective tissue disease (MCTD) and systemic lupus erythematosus (SLE). Specific HLA-Dw4 and HLA-DR4 subtypes are more frequent in MCTD patients, suggesting distinct genetic underpinnings for these autoimmune conditions.
Area of Science:
- Immunogenetics
- Rheumatology
- Human Leukocyte Antigen (HLA) complex
Background:
- Mixed Connective Tissue Disease (MCTD) and Systemic Lupus Erythematosus (SLE) are autoimmune disorders with overlapping clinical features.
- Previous research suggests a potential genetic predisposition, particularly involving the Human Leukocyte Antigen (HLA) system, in the pathogenesis of these diseases.
- Understanding the specific HLA associations can help differentiate between MCTD and SLE and elucidate their distinct etiological pathways.
Purpose of the Study:
- To investigate and compare the frequencies of specific HLA-A, B, C, Dw, and DR antigens in patients diagnosed with MCTD and SLE.
- To identify potential genetic markers that distinguish MCTD from SLE based on HLA antigen profiles.
- To explore the relationship between specific HLA subtypes and the distinct clinical manifestations of these autoimmune diseases.
Main Methods:
- Human Leukocyte Antigen (HLA) typing was performed on 32 patients with MCTD and 60 patients with SLE.
- Patients with SLE met at least four American College of Rheumatology criteria for SLE.
- Patients with MCTD met the criteria proposed by Alarcon-Segovia (1989), with antibodies to Sm not being an exclusion criterion.
Main Results:
- Patients with SLE showed increased frequencies of HLA-Dw3, DR3, and associated B8 and A1 antigens.
- Patients with MCTD exhibited a significantly higher frequency of HLA-Dw4 (45%) compared to controls (18%) and SLE patients (14%).
- A strong association was observed between MCTD and HLA-DR4 (52% in MCTD vs. 28% in controls), particularly with the Dw4 subtype and the B15, DR4 combination.
Conclusions:
- The genetic background, specifically HLA antigen profiles, appears to differ significantly between patients with MCTD and SLE.
- The increased frequency of HLA-Dw4 and HLA-DR4 subtypes in MCTD patients suggests a distinct genetic susceptibility.
- These genetic differences may contribute to the observed clinical heterogeneity between MCTD and SLE.
Abstract:
Patients with mixed connective tissue disease (MCTD, n = 32) or systemic lupus erythematosus (SLE, n = 60) were typed for HLA-A, B, C, Dw, and DR antigens. All patients with SLE fulfilled at least four criteria of SLE and the patients with MCTD met the criteria proposed by Alarcon-Segovia (1989). The presence of antibodies to Sm was not considered as an exclusion for MCTD. In the patients with SLE, Dw3, DR3, and the associated B8 and A1 antigens were increased, whereas in the patients with MCTD an increased frequency of Dw4 was found (45 v 18% in controls v 14% in SLE). Of the subtypes of DR4, Dw4 was present in all but one of the DR4 positive patients. The frequency of DR4 in patients with MCTD (52%) differed significantly from that of controls (28%). The strong association of MCTD to one DR4 subtype was further seen in the significantly increased frequency of the B15, DR4 combination. Thus the genetic background seems to be different in patients with MCTD from that in patients with SLE. This could partly explain the clinical differences between these diseases.