Heart failure, a leading cause of death in humans, can emanate from myocarditis. Although most individuals with myocarditis recover spontaneously, some develop chronic dilated cardiomyopathy. Myocarditis may result from both infectious and noninfectious causes, including autoimmune responses to cardiac antigens. In support of this notion, intracellular cardiac antigens, like cardiac myosin heavy chain-a, cardiac troponin-I, and adenine nucleotide translocator 1 (ANT 1 ), have been identified as autoantigens in cardiac autoimmunity. Herein, we demonstrate that ANT 1 can induce autoimmune myocarditis in A/J mice by generating autoreactive T cells. We show that ANT 1 encompasses multiple immunodominant epitopes (namely, ANT 1 21-40, ANT 1 31-50, ANT 1 171-190, and ANT 1 181-200). Although all four peptides induce comparable T-cell responses, only ANT 1 21-40 was found to be a major myocarditogenic epitope in immunized animals. The myocarditis-inducing ability of ANT 1 21-40 was associated with the generation of T cells producing predominantly IL-17A, and the antigen-sensitized T cells could transfer the disease to naïve recipients. These data indicate that cardiac mitochondrial proteins can be target autoantigens in myocarditis, supporting the notion that the antigens released as a result of primary damage may contribute to the persistence of chronic inflammation through autoimmunity. Myocarditis can occur as a result of exposure to various infectious and noninfectious insults, but does not generally lead to a fatal outcome (ie, most affected individuals can recover spontaneously). However, a proportion of those affected can develop dilated cardiomyopathy (DCM). Estimates indicate that approximately half of DCM patients undergo heart transplantation because of a lack of alternative therapeutic options.1e3 Furthermore, several clinical studies suggest that DCM patients can have autoantibodies to several cardiac antigens, including adenine nucleotide translocator (ANT).4e6 Because DCM can arise as a sequel to myocarditis, it has been postulated that autoimmune response may be an underlying mechanism in its pathogenesis. 7ANT exists in multiple isoforms, all four of which are expressed in humans (ANT 1 , ANT 2 , ANT 3 , and ANT 4 ), but only three in mice (ANT 1 , ANT 2 , and ANT 4 ). ANT 1 is expressed in muscle tissues (heart and skeletal) and the brain, ANT 2 can be expressed in liver, kidney, and heart, and ANT 4 expression is restricted to the testes in mice.

IntroductionOrgan‐specific autoimmune diseases are believed to result from immune responses generated against self‐antigens specific to each organ. However, when such responses target antigens expressed promiscuously in multiple tissues, then the immune‐mediated damage may be wide spread.MethodsIn this report, we describe a mitochondrial protein, branched chain α‐ketoacid dehydrogenase kinase (BCKDk) that can act as a target autoantigen in the development of autoimmune inflammatory reactions in both heart and liver.ResultsWe demonstrate that BCKDk protein contains at least nine immunodominant epitopes, three of which, BCKDk 71–90, BCKDk 111–130 and BCKDk 141–160, were found to induce varying degrees of myocarditis in immunized mice. One of these, BCKDk 111–130, could also induce hepatitis without affecting lungs, kidneys, skeletal muscles, and brain. In immunogenicity testing, all three peptides induced antigen‐specific T cell responses, as verified by proliferation assay and/or major histocompatibility complex class II/IAk dextramer staining. Finally, the disease‐inducing abilities of BCKDk peptides were correlated with the production of interferon‐γ, and the activated T cells could transfer disease to naive recipients.ConclusionsThe disease induced by BCKDk peptides could serve as a useful model to study the autoimmune events of inflammatory heart and liver diseases.

We postulated that changes in the cell surface display of molecules that facilitate cell-cell and cell-matrix adhesions may reflect the changing immunosurveillance capacity of blood monocytes during progression of human immunodeficiency virus (HIV) infections. In Centers for Disease Control (CDC) stage A patients, whose monocytes' ability to phagocytose bacteria and generate reactive oxygen intermediates is often increased, the frequency of monocytes expressing CD49d, HLA-DP, HLA-DQ, and an activation epitope of CD11a/CD18 was increased and monocyte transendothelial migration was unimpaired. In CDC stage B/C patients, whose monocytes' ability to phagocytose bacteria and migrate across confluent endothelial monolayers was diminished, surface expression of CD49e and CD62L and the percentage of monocytes expressing CD18, CD11a, CD29, CD49e, CD54, CD58, CD31, and HLA-I were significantly decreased. Incubating normal donor monocytes with immune complexes in vitro reproduced the phenotypic and functional abnormalities seen in stage B/C patients. By contrast, in vitro stimulation with subcellular particulates released by apoptotic lymphocytes reproduced changes seen in stage A patients' monocytes. Although circulating monocytes appear to be activated at all stages, these data suggest that the high levels of circulating immune complexes, found predominantly in the later stages of HIV infection, may be particularly instrumental in reducing the monocyte's capacity to maintain surveillance against infection. (J. Clin. Invest. 1995. 95:1690-1701

BackgroundWe recently reported the identification of Bacillus sp. NRRL B-14911 that induces heart autoimmunity by generating cardiac-reactive T cells through molecular mimicry. This marine bacterium was originally isolated from the Gulf of Mexico, but no associations with human diseases were reported. Therefore, to characterize its biological and medical significance, we sought to determine and analyze the complete genome sequence of Bacillus sp. NRRL B-14911.ResultsBased on the phylogenetic analysis of 16S ribosomal RNA (rRNA) genes, sequence analysis of the 16S-23S rDNA intergenic transcribed spacers, phenotypic microarray, and matrix-assisted laser desorption ionization time-of-flight mass spectrometry, we propose that this organism belongs to the species Bacillus infantis, previously shown to be associated with sepsis in a newborn child. Analysis of the complete genome of Bacillus sp. NRRL B-14911 revealed several virulence factors including adhesins, invasins, colonization factors, siderophores and transporters. Likewise, the bacterial genome encodes a wide range of methyl transferases, transporters, enzymatic and biochemical pathways, and insertion sequence elements that are distinct from other closely related bacilli.ConclusionsThe complete genome sequence of Bacillus sp. NRRL B-14911 provided in this study may facilitate genetic manipulations to assess gene functions associated with bacterial survival and virulence. Additionally, this bacterium may serve as a useful tool to establish a disease model that permits systematic analysis of autoimmune events in various susceptible rodent strains.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2900-2) contains supplementary material, which is available to authorized users.

The advent of major histocompatibility complex (MHC) tetramer technology has been a major contribution to T cell immunology, because tetramer reagents permit detection of antigen-specific T cells at the single-cell level in heterogeneous populations by flow cytometry. However, unlike MHC class I tetramers, the utility of MHC class II tetramers has been less frequently reported. MHC class II tetramers can be used successfully to enumerate the frequencies of antigen-specific CD4 T cells in cells activated in vitro, but their use for ex vivo analyses continues to be a problem, due in part to their activation dependency for binding with T cells. To circumvent this problem, we recently reported the creation of a new generation of reagents called MHC class II dextramers, which were found to be superior to their counterparts. In this review, we discuss the utility of class II dextramers vis-a-vis tetramers, with respect to their specificity and sensitivity, including potential applications and limitations.