Anti-CD180 monoclonal antibody, clone RP/14

Background: Toll-like receptor-4 (TLR4), a receptor of the innate immune system, is suggested to have detrimental effects on cardiac function after myocardial infarction (MI). RP105 (CD180) is a TLR4 homolog lacking the intracellular signaling domain that competitively inhibits TLR4-signaling. Thus, we hypothesized that RP105 deficiency, by amplifying TLR4 signaling, would lead to aggravated cardiac dysfunction after MI. Methods and results: First, whole blood from RP105(-/-) and wild-type (WT) male C57Bl/6N mice was stimulated with LPS, which induced a strong inflammatory TNF alpha response in RP105(-/-) mice. Then, baseline heart function was assessed by left ventricular pressure-volume relationships which were not different between RP105(-/-) and WT mice. Permanent ligation of the left anterior descending coronary artery was performed to induce MI. Infarct sizes were analyzed by (immuno) histology and did not differ. Fifteen days post MI heart function was assessed and RP105(-/-) mice had significantly higher heart rate (+ 21%, P < 0.01), end systolic volume index (+ 57%, P < 0.05), end systolic pressure (+ 22%, P < 0.05) and lower relaxation time constant tau (-12%, P < 0.05), and a tendency for increased end diastolic volume index (+ 42%, P < 0.06), compared to WT mice. In the area adjacent to the infarct zone, compared to the healthy myocardium, levels of RP105, TLR4 and the endogenous TLR4 ligand fibronectin-EDA were increased as well as the number of macrophages, however this was not different between both groups. Conclusion: Deficiency of the endogenous TLR4 inhibitor RP105 leads to an enhanced inflammatory status and more pronounced cardiac dilatation after induction of MI, underscoring the role of the TLR4 pathway in post-infarction remodeling. (C) 2014 Elsevier Ireland Ltd. All rights reserved.

A hallmark of systemic lupus erythematosus (SLE) is the consistent production of various auto-antibodies by auto-reactive B cells. Interferon-alpha (IFN-alpha) signaling is highly activated in SLE B cells and plays a vital role in the antibody response by B cells. Previous studies have shown that CD180-negative B cells, which are dramatically increased in SLE patients, are responsible for the production of auto-antibodies. However, the association between CD180 and IFN-alpha signaling remains unknown. In the present study, we explored the effect of CD180 on regulating the activation of IFN-alpha signaling in B cells. We found that the number of CD180-negative B cells was increased in MRL/Mp-Fas(lpr/lpr) lupus-prone mice compared with wild-type mice. Phenotypic analysis showed that CD180-negative B cells comprised CD138(+) plasmablast/plasma cells and GL-7(+) germinal center (GC) B cells. Notably, ligation of CD180 significantly inhibited the IFN-alpha-induced phosphorylation of signal transducer and activator of transcription 2 (STAT-2) and expression of IFN-stimulated genes (ISGs) in a Lyn-PI3K-BTK-dependent manner in vitro. Moreover, ligation of CD180 could also inhibit IFN-alpha-induced ISG expression in B cells in vivo. Furthermore, the Toll-like receptor 7 and Toll-like receptor 9 signaling pathways could significantly downregulate CD180 expression and modulate the inhibitory effect of CD180 signaling on the activation of IFN-alpha signaling. Collectively, our results highlight the close association between the increased proportion of CD180-negative B cells and the activation of IFN-alpha signaling in SLE. Our data provide molecular insight into the mechanism of IFN-alpha signaling activation in SLE B cells and a potential therapeutic approach for SLE treatment.