Key result
Adult patients with idiopathic inflammatory myopathies had significantly increased frequencies of CD19+ B cells (14.8% vs 7.7%) and naïve B cells, but decreased memory B cells compared to healthy controls.
Why the study?
Although abnormalities and hyperactivation of B cells occur in idiopathic inflammatory myopathies, little is known about changes in peripheral blood B cell homeostasis in adult patients.
Case-Control (n=40)
No
Absolute Event Rate: 14.8% vs 7.7%
p-value: p=0.005
Adult IIM patients exhibit abnormal peripheral B cell homeostasis characterized by expanded CD19+ and naïve B cells and reduced memory B cells, which correlates with clinical features like rash and anti-MDA5 positivity.
Altered B cell subsets in IIM should not yet change practice; leaves open their diagnostic or therapeutic utility.
OBJECTIVES: Abnormalities and hyperactivation of B cells have been described in idiopathic inflammatory myopathies (IIM). However, little is known about changes in the homeostasis of peripheral blood B cells in adult IIM patients. The aim of this study was to identify phenotypic alterations of B cell subsets and their relation to the overall clinical profile. METHODS: Blood samples were collected from 25 adult IIM patients and 15 healthy controls. Peripheral B cell subsets were classified into non-switched memory B cells (CD19+CD27+lgD+), switched memory B cells (CD19+CD27+lgD-), double-negative (DN) memory B cells (CD19+CD27-lgD-) and naïve B cells (CD19+CD27-lgD+) based on their surface phenotype as measured by flow cytometry. The clinical profile of IIM and its correlation with B cell subsets was further evaluated. RESULTS: Frequencies of CD19+ B cells and naïve B cells were increased in adult IIM patients compared with healthy controls (p=0.005 and p<0.001, respectively) and the frequency of memory B cells was decreased (p<0.001). Moreover, patients with a rash had lower non-switched memory B cells proportion (p=0.032). Patients with anti-MDA5+ antibodies had higher CD19+ B cells proportion than anti-ARS+ patients (p=0.046). Patients who were not receiving treatment had elevated levels of CD19+ B cells and naïve B cells along with reduced non-switched memory B cells compared with patients who were receiving treatment (p=0.021, p=0.036 and p=0.032, respectively). CONCLUSIONS: Our findings demonstrate abnormalities in the homeostasis of the B cell subsets present in adult IIM patients, characterised by expanded CD19+ B cells and naïve B cells but reduced memory B cells. Phenotypic abnormalities of B cell subsets are associated with the presence of a rash, with anti-MDA5 positivity and with treatment.
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Wang et al. (2022) conducted a case-control in Idiopathic inflammatory myopathies (n=40). Idiopathic inflammatory myopathies vs. Healthy controls was evaluated on Frequency of CD19+ B cells (p=0.005). Adult patients with idiopathic inflammatory myopathies had significantly increased frequencies of CD19+ B cells (14.8% vs 7.7%) and naïve B cells, but decreased memory B cells compared to healthy controls.
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