Aberrant dendritic cell subsets in patients with myasthenia gravis and related clinical features

<b><i>Introduction:</i></b> Dendritic cells (DCs) play critical roles in the pathogenesis of myasthenia gravis (MG), and a series of DC-based experimental strategies for MG have recently been developed. However, the definite roles of different DC subsets in the mechanism of MG have scarcely been covered by previous studies. The present study aimed to investigate the levels of three main DC subsets, plasmacytoid DCs (pDCs) (CD303 positive) and two distinct subsets of conventional DCs (cDCs), namely CD1c⁺ cDCs and CD141⁺ cDCs, in MG patients and analyze related clinical features. <b><i>Methods:</i></b> From January 2016 to December 2020, 160 newly diagnosed MG patients and matched healthy controls (<i>n</i> = 160) were included in the study, and their clinical data were collected. The blood samples from MG patients before treatment and controls were collected for flow cytometry analysis. A total of 14 MG thymoma, 24 control thymoma, and 3 thymic cysts were used to immunostain the DC subsets. <b><i>Results:</i></b> The flow cytometry analysis showed a significantly higher frequency of circulating pDCs, CD1c⁺ cDCs, and CD141⁺ cDCs in MG patients than in healthy controls (<i>p</i> &lt; 0.001 for all). Patients with early-onset MG (&lt;50 years old) had a lower frequency of circulating pDCs but a higher frequency of circulating CD1c⁺ cDCs than those with late-onset MG (≥50 years old) (<i>p</i> = 0.014 and <i>p</i> = 0.025, respectively). The frequency of circulating pDCs was positively associated with the clinical severity of late-onset MG patients (<i>r</i> = 0.613, <i>p</i> &lt; 0.001). 64.3% (9/14) of MG thymoma is of type B2 under the World Health Organization classification, which is higher than that in control thymoma (33.3%, 8/24) (<i>p</i> = 0.019). For type B2 thymoma, there were significantly more pDCs but fewer CD1c⁺ cDCs in MG thymoma than in the controls. <b><i>Conclusion:</i></b> The distribution of aberrant pDCs, CD1c⁺ cDCs, and CD141⁺ cDCs in MG patients displayed age- and thymoma-related differences, which may contribute to the impaired immune tolerance and lead to the onset of MG.