Inhibition of experimental autoimmune myocarditis: peripheral deletion of TcR Vβ 8.1, 8.2+ CD4+ T cells in TLR-4 deficient mice

Toll-like receptors (TLR) are pattern recognition receptors that are an essential feature of host defense against pathogens. Expression of TLR-4 on dendritic cells was reported to be required for initiation of experimental autoimmune myocarditis (EAM) but the mechanism by which TLR-4 signaling affects autoimmunity is incompletely understood. To determine the role of TLR-4 in EAM, wild type and TLR-4−/− mice were immunized with myosin peptide (614–629) in CFA. TLR-4−/− mice demonstrated decreased myosin specific proliferation and decreased production of INF-γ and IL-2. Immunization with myosin induced greater severity of myocarditis in wild type compared to TLR-4−/− mice as evidenced by lesions in the myocardium. TcR Vβ 8.1, 8.2+ CD4+ T cells, detected in lesions were isolated from splenocytes by flow cytometry and found to undergo increased apoptosis in TLR-4−/− mice. In situ immunohistochemistry showed increased colocalization of cleaved caspase 3 and TcR Vβ 8.1, 8.2+ CD4+ T cells in TLR-4−/− mice compared to wild type. Increased apoptosis was associated with impaired activation of NF-kB p65 and decreased cell viability in the presence of TNF-α. These results demonstrate that infiltrating TcR Vβ 8.1, 8.2+ CD4+ T cells are deleted by the mechanism of apoptosis in TLR-4−/− mice with EAM.