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Purpose: Excessive inflammation responses mediated by CD4(+) T cells contributes to myocardial fibrosis in dilated cardiomyopathy (DCM) resulting from viral myocarditis. Recently, some scholars discovered that B cells harbored an abnormal pro-inflammatory capacity besides the production of autoantibodies. Thus, we aimed to explore whether and which type of B cells act on myocardial fibrosis in DCM., Methods: A total of 56 newly hospitalized DCM patients were studied, and among these, 17 patients accepted the gadolinium enhanced cardiovascular magnetic resonance imaging (MRI) for myocardial fibrosis evaluations., Results: B cell functions including the frequency and proliferation were significantly elevated in DCM patients. After screening the important cytokines including IL-1β, IL-6, IL-10, IL-17, TNF-α and TGF-β produced in these B cells by flow cytometry, we found that only the TNF-α-secreting B cells were obviously increased. Furthermore, the TNF-α protein secretion and mRNA levels were also enhanced in LPS-stimulated B cell isolated from DCM patients. In addition, 10 patients (59%) with increased TNF-α-secreting B cells showed late enhancement and boosted serum procollagen type III compared with the other 7 patients (41%) whose enhancement could not be detected. Moreover, the frequencies of TNF-α-secreting B cells were negatively correlated with LVEF and positively correlated with LVEDD, NT-proBNP and procollagen type III in all of the DCM patients., Conclusions: Our study firstly suggested that TNF-α-secreting B cells were involved in myocardial fibrosis, which revealed the new pathogenic mechanism of B cells in DCM, and therapeutic targets against these cells might be valuable.

Background: Recently, the Th17 cell, a newly determined CD4+Th subset, was reported to participate in the inflammation of myocarditis combined with Th1 cells, and this study aimed to explore whether it was involved in the Th2 cell-mediated humoral immunity in viral myocarditis., Methods: A total of 34 patients, including 16 acute viral myocarditis (AVMC) and 18 dilated cardiomyopathy (DCM) having a history of AVMC, were enrolled for this study besides 18 healthy volunteers., Results: The frequencies of Th17 and Th1 cells, especially Th17 cells in AVMC patients, while those of Th1 and Th2 cells, especially Th2 cells in DCM group, were all increased significantly compared with those in healthy volunteers (P < 0.01), with no changes of Th2 cells in AVMC and Th17 cells in DCM groups. The similar results were also observed in Th cell cytokines (IL-17, INF-gamma, and IL-4) and key transcript factors (RORgammat, T-bet, and GATA-3). Meanwhile, antiheart antibodies (AHA) of IgG type were found in 15 (93.8%) patients with AVMC and ten (55.6%) cases with DCM, accompanied by the higher expression of IL-17R on B cells and the frequencies of B cells than those in healthy controls (P < 0.01 in AVMC and P < 0.05 in DCM, respectively) who had no AHA. Furthermore, both of the B cell activities in AVMC and DCM groups were elevated and positively correlated to serum IL-17 (R = 0.66, P < 0.01) and IL-4 (R = 0.47, P < 0.05) respectively, with no correlation to INF-gamma., Conclusions: It was Th17 cells but not Th2 cells that helped the B cells to produce AHA in AVMC and not until at the late phase of viral myocarditis could Th2 cells play the important role in mediating humoral response.

CD4 T cells are suspected to play an important role in the pathogenesis of dilated cardiomyopathy (DCM). This study sought to evaluate whether anti-L3T4 monoclonal antibody (McAb) could induce the infectious tolerance to the adenosine diphosphate (ADP)/adenosine triphosphate (ATP) carrier peptides to protect mice from DCM. BALB/c mice (n = 16) were immunized with the peptides derived from human ADP/ATP carrier on the 1st, 14th, 28th, 49th, and 79th days, and some of them (n = 6) were also injected with anti-L3T4 McAb on the -1st, 0, and 1st days. On the 180th day, the splenocytes (SC) from the McAb-treated group were transferred into the syngeneic recipients (n = 6) who were also immunized with the peptides in the same manner. The sham-immunized mice were taken as the controls (n = 10). Results showed that the serum antibody against the ADP/ATP carrier examined with ELISA was positive in all mice only immunized with the peptides (DCM group), while negative in the McAb-treated, the SC-transferred, and the Control groups. The mRNA expression of IFN-gamma, IL-2, and IL-4, especially IL-4 in T cells investigated using real-time quantitative PCR and the percentages of T helper 1 (Th1) and Th2 subsets, especially Th2 subset detected with Flow Cytometry were all increased in DCM group, accompanied by the cardiac histopathological changes like those in DCM. Such findings were not seen in the other three groups. It concluded that anti-L3T4 McAb could inhibit the occurrence of DCM induced by the ADP/ATP carrier peptides in mice, and this immune tolerance could be transferred to the syngeneic recipients.