A 32-year-old woman from Mumbai with a 2-year history of SLE (ANA positive, anti-dsDNA positive, anti-Smith positive) presents with acute onset dyspnea, pleuritic chest pain, and a new pericardial friction rub on auscultation. Chest X-ray shows bilateral pleural effusions. Echocardiography reveals a small pericardial effusion without tamponade. Complete blood count shows hemoglobin 9.2 g/dL, WBC 3,200/μL, and platelets 95,000/μL. Which of the following pathologic mechanisms best explains the pleural and pericardial involvement in this patient?