Abstract 5261: Platelet-Depletion Ameliorates Cardiac Function and Disease Severity in Experimental Autoimmune Myocarditis
Introduction: Experimental Autoimmune Myocarditis (EAM) is a CD4+ T cell mediated model of inflammatory cardiomyopathy. Activated platelets express CD154, a molecule critical to adaptive immune responses, which has been implicated in platelet-mediated modulation of inflammation.
Hypothesis: Platelets are critical for the generation of heart-specific, autoreactive T-cell responses in a model of experimental Autoimmune Myocarditis.
Methods: BALB/c mice were immunized twice at day 0 and day 7 with 100μg alpha-MyHC-peptide (614–29) together with Complete Freund‘s adjuvant. Platelets were markedly depleted by i.v. injection of a GP1alpha antibody every 5th day (n=8). Control mice were injected with a non-depleting isotype antibody (n=8). Mice were assessed at day 28 for heart dimensions and cardiac function using echocardiography. After lethal anesthesia, hearts were removed and analyzed for heart weight/body weight ratio and histological severity scores. CD4+ T-cells were isolated from spleens, and analyzed for CD154 and IL-17 expression using FACS after in vitro re-stimulation on alpha-MyHC pulsed, irradiated antigen presenting cells.
Results: Modest platelet depletion protected from left ventricular dilatation, and preserved left ventricular ejection fraction in immunized mice. Myocarditis prevalence and severity scores were significantly reduced in depleted animals. Relative numbers of spleen-derived CD4+ T-cells expressing CD154 or IL-17, were significantly reduced in the treatment group (table⇓).
Conclusion: Our findings suggest that platelets might play a critical role in the development of heart-specific autoimmunity and cardiomyopathy. Further studies are needed to confirm these findings, which suggest a novel treatment approach for inflammatory cardiomyopathy.