Blocking FcRn in humans reduces circulating IgG levels and inhibits IgG immune complex-mediated immune responses.

The neonatal crystallizable fragment receptor (FcRn) functions as an intracellular protection receptor for immunoglobulin G (IgG). Recently, several clinical studies have reported the lowering of circulating monomeric IgG levels through FcRn blockade for the potential treatment of autoimmune diseases. Many autoimmune diseases, however, are derived from the effects of IgG immune complexes (ICs). We generated, characterized, and assessed the effects of SYNT001, a FcRn-blocking monoclonal antibody, in mice, nonhuman primates (NHPs), and humans. SYNT001 decreased all IgG subtypes and IgG ICs in the circulation of humans, as we show in a first-in-human phase 1, single ascending dose study. In addition, IgG IC induction of inflammatory pathways was dependent on FcRn and inhibited by SYNT001. These studies expand the role of FcRn in humans by showing that it controls not only IgG protection from catabolism but also inflammatory pathways associated with IgG ICs involved in a variety of autoimmune diseases.

TGF-beta1 modulates Foxp3 expression and regulatory activity in distinct CD4+ T cell subsets.

Although forkhead box p3 (Foxp3) expression is restricted to naturally occurring CD4(+) regulatory T cells (T(REG)), little is known about the various signals that regulate it in T cells. As TGF-beta has been reported to modulate Foxp3 expression in T cells, we investigated its effects on the induction or maintenance of regulatory functions in different CD4(+) T cell subsets. TGF-beta1 priming was able to promote differentiation of T(REG) cells from nonregulatory CD4(+)CD25(-) T cells in a concentration-dependent manner through Foxp3 induction. As CD4(+)CD25(-) T cells remain a highly heterogeneous population with variable degrees of antigen experience, we then examined the effect of TGF-beta1 on naive CD4(+)CD25(-)CD45RB(HIGH) T cells. Freshly isolated or TGF-beta1-treated CD4(+)CD25(-)CD45RB(HIGH) T cells never displayed any regulatory functions or significant Foxp3 expression following TCR activation. In stark contrast, freshly isolated CD4(+)CD25(-)CD45RB(LOW) cells, albeit expressing low levels of Foxp3 mRNA and protein, were unable to suppress CD4(+) effector T cell proliferation but acquired regulatory activity and de novo Foxp3 expression following TGF-beta1 exposure. Furthermore, suppression was IL-10-dependent, as anti-IL-10 receptor antibody treatment abrogated this suppression completely, consistent with the ability of TGF-beta1-treated CD4(+)CD25(-)CD45RB(LOW) to synthesize IL-10 upon restimulation in vitro. Last, we show that TGF-beta1 treatment or blockade did not lead to enhanced expansion or function of naturally occurring CD4(+)CD25(+) T(REG) cells, although it maintained Foxp3 mRNA and protein expression. Altogether, TGF-beta1 promotes the induction of IL-10-secreting CD4(+) T(REG) cells from CD4(+)CD25(-)CD45RB(LOW) precursors through de novo Foxp3 production and maintains natural T(REG) cell peripheral homeostasis by sustaining Foxp3 expression.

Control of type 1 autoimmune diabetes by naturally occurring CD4+CD25+ regulatory T lymphocytes in neonatal NOD mice.

Nonobese diabetic (NOD) mice serve as a model of spontaneous type 1 diabetes (T1D), a T cell-mediated autoimmune disease leading to the destruction of pancreatic insulin-producing beta islet cells. A possible deficiency in regulatory T (T(reg)) cell development or function may promote the activation, expansion, and recruitment of autoreactive T cells and the onset of T1D. Naturally occurring CD4(+)CD25(+) T(reg) (nT(reg)) cells, which typically display potent inhibitory effects on T cell functions in vitro and in vivo, may be defective at controlling autoimmunity in T1D. We have examined the relative contribution of CD4(+)CD25(+) nT(reg) cells in the immune regulation of T1D in the NOD mouse model. CD4(+)CD25(+) T cells represent 5-10% of CD4(+) thymocytes or peripheral T cells from prediabetic neonatal NOD mice, are anergic to TCR signals, and potently suppress activated T cells in a contact-dependent and cytokine-independent fashion in vitro. Unlike total CD4(+) T cells, prediabetic CD25(+)-depleted CD4(+) T cells are potently diabetogenic when transferred in immunodeficient NOD mice. Co-transfer of CD4(+)CD25(+) T cells from thymocytes or peripheral lymphoid tissues of neonatal NOD mice dramatically halts disease development and beta-islet cell lymphocytic infiltration, even when T1D is induced by CD4(+) T cells from BDC2.5 transgenic or diabetic NOD mice. Finally, we show that CD4(+)CD25(+) T(reg) preferentially accumulate in inflamed pancreatic environments, where they potently inhibit the antigen-specific expansion and cytokine effector functions of diabetogenic T cells. Thus, CD4(+)CD25(+) T cell-mediated regulation is operative in the prediabetic neonatal T cell repertoire and can suppress the diabetogenic process and control the onset of T1D.

Plasma lactate dehydrogenase and creatine kinase after anaerobic exercise.

Eight untrained men performed 15-s and 60-s high-intensity exercise on a bicycle ergometer. Activities of the creatine kinase (CK) and lactate dehydrogenase (LDH) were measured in blood 3 min and 2, 6, and 24 h after cessation of exercise. The results indicate that anaerobic exercise induces a transient increase in plasma LDH activity and a more prolonged elevation in plasma CK activity. A negative correlation was found between CK activity measured before and 3 min after exercise and mean power, and total external work performed in both test types. A similar correlation was ascertained between pre- and post-exercise CK activity and maximal power output measured in the 60-s test. After the 15-s exercise test, only post-exercise plasma CK activity was negatively correlated with the maximal power output.