The Complement System in an Argentinian Cohort of Myasthenia Gravis Patients:Evaluation of Soluble Proteins and Membrane-Bound Regulators

JUSTO ME; AGUIRRE F; LEONI J; VILLA A; PAZ ML

Congreso; 16th ISNI Congress; 2023

Myasthenia gravis (MG) is an autoimmune disease characterized by autoantibody-mediated dysfunction at the neuromuscular junction. These autoantibodies primarily target the acetylcholine receptor, triggering activation of the complement system's classical pathway, which leads to muscle fibre destruction. The complement system consists of over 50 proteins, many of which are involved in regulating the activation sequence. Although various complement regulator proteins (CRPs) have been evaluated in animal models, their study in MG patients remains limited.To address this gap, we assessed the expression of three membrane-bound CRPs, namely CD59, CD46, and CD55, on white blood cells (WBCs) from 15 MG patients and 8 healthy controls (HCs). The severity of MG was assessed and recorded using ADL and MGC clinical scores. Blood samples were collected in heparinized tubes and processed 24 hours later. After red blood cell lysis, WBCs were incubated with monoclonal antibodies against CD59-FITC, CD55-APC, and CD46-PE for 30 minutes at room temperature. Flow cytometry analysis was conducted to measure the expression of these markers on the WBCs' granulocyte subpopulation, which is known to exhibit the highest CRP expression, and represents the most abundant cell population among WBCs. Additionally, plasma levels of complement C3, C4 and C5a proteins were measured in the samples.Our findings revealed a lower mean fluorescence intensity (MFI) for all three CRPs on granulocytes in MG patients compared to HCs. However, only CD46 expression (MFI) exhibited a statistically significant difference compared to HCs (MG: 5649 ± 1628 vs HCs: 7680 ± 1591, p=0.009). Preliminary analysis of this small patient group did not identify a statistically significant correlation between CRP expression and MG severity nor between CRP expression and C3, C4 and C5a plasma levels. In conclusion, this study suggests that diminished expression of these three CRPs, particularly CD46, may contribute to increased susceptibility to complement-mediated damage in MG patients. However, further investigations involving a larger participant cohort are necessary to validate these findings.