Circulating C1q levels in health and disease, more than just a biomarker

C1q is the recognition molecule of the classical pathway of the complement system. By binding to its targets, such as antigen-bound immunoglobulins or C-reactive protein, C1q contributes to the innate defense against infections. However, C1q also plays several other roles beyond its traditional role in complement activation. Circulating levels of C1q are determined in routine diagnostics as biomarker in several diseases. Decreased C1q levels are present in several autoimmune conditions. The decreased levels reflect the consumption of C1q by complement activation and serves as a biomarker for disease activity. In contrast, increased C1q levels are present in infectious and inflammatory diseases and may serve as a diagnostic biomarker. The increased levels of C1q are still incompletely understood but are suggested to modulate the adaptive immune response as C1q is known to impact on the maturation status of antigen-presenting cells and C1q impacts directly on T cells leading to decreased T-cell activity in high C1q conditions. In this review, we provide a comprehensive overview of the current literature on circulating levels of C1q in health and disease, and discuss how C1q can both protect against infections as well as maintain tolerance by regulating adaptive immunity.Nephrolog

Decreased IL7Rα and TdT expression underlie the skewed immunoglobulin repertoire of human B-cell precursors from fetal origin

Newborns are unable to mount antibody responses towards certain antigens. This has been related to the restricted repertoire of immunoglobulin (Ig) genes of their B cells. The mechanisms underlying the restricted fetal Ig gene repertoire are currently unresolved. We here addressed this with detailed molecular and cellular analysis of human precursor-B cells from fetal liver, fetal bone marrow (BM), and pediatric BM. In the absence of selection processes, fetal B-cell progenitors more frequently used proximal V, D and J genes in complete IGH gene rearrangements, despite normal Ig locus contraction. Fewer N-nucleotides were added in IGH gene rearrangements in the context of low TdT and XRCC4 expression. Moreover, fetal progenitor-B cells expressed lower levels of IL7Rα than their pediatric counterparts. Analysis of progenitor-B cells from IL7Rα-deficient patients revealed that TdT expression and N-nucleotides additions in Dh-Jh junctions were dependent on functional IL7Rα. Thus, IL7Rα affects TdT expression, and decreased expression of this receptor underlies at least in part the skewed Ig repertoire formation in fetal B-cell precursors. These new insights provide a better understanding of the formation of adaptive immunity in the developing fetus

The role of variable domain glycosylation of antibodies in immunity

Immunoglobulin G (IgG) is the most abundant class of immunoglobulins in the blood, and 15-25% of IgG molecules contain Fab glycans in addition to the Fc glycans that are present in all IgG molecules. The emergence of Fab-glycosylated antibodies, starting from largely absent in the initial antibody repertoire of naive B cells, was mostly unexplored. We found that Fab glycosylation sites mainly emerge near the antigen-binding site, explaining the potential of Fab glycans to influence antigen binding. The differences in Fab glycosylation between antigen specificities indicate antigen-associated selection. In addition to their influence on antigen binding, we found that Fab glycans can contribute to antibody stability. Our results suggest that Fab glycans are exposed to different degrees, possibly explaining why some Fab glycans do have an effect on antigen binding and/or antibody stability and others do not. IgG4 antibody responses are associated with tolerance, and the increased Fab glycosylation of this subclass might suggest a role for Fab glycans in immune modulation. Interestingly, our preliminary in vivo experiments indicate that Fab glycosylated drug antibodies are less immunogenic than drug antibodies without Fab glycans, again suggesting a role for Fab glycans in immune modulation. Together, the results presented in this thesis show that Fab glycans can affect antigen binding and antibody stability, and our findings suggest that future research on the possible immunomodulatory role for Fab glycans in immunity could be very useful and eventually possibly contribute to improve antibody therapies

Human DC-SIGN and CD23 do not interact with human IgG

Proteomic

Unique patterns of glycosylation in immunoglobulin subclass G4-related disease and primary sclerosing cholangitis

Proteomic

Inhibition of Fc gamma R-mediated phagocytosis by IVIg is independent of IgG-Fc sialylation and Fc gamma RIIb in human macrophages

Proteomic

Right Ventricular and Right Atrial Function Are Less Compromised in Pulmonary Hypertension Secondary to Heart Failure With Preserved Ejection Fraction: A Comparison With Pulmonary Arterial Hypertension With Similar Pressure Overload

Background: Heart failure with preserved ejection fraction (HFpEF) is a prevalent disorder for which no effective treatment yet exists. Pulmonary hypertension (PH) and right atrial (RA) and ventricular (RV) dysfunction are frequently observed. The question remains whether the PH with the associated RV/RA dysfunction in HFpEF are markers of disease severity. Methods: To obtain insight in the relative importance of pressure-overload and left-to-right interaction, we compared RA and RV function in 3 groups: 1. HFpEF (n=13); 2. HFpEF-PH (n=33), and; 3. pulmonary arterial hypertension (PAH) matched to pulmonary artery pressures of HFpEF-PH (PH limited to mPAP >= 30 and <= 50 mmHg) (n=47). Patients underwent right heart catheterization and cardiac magnetic resonance imaging. Results: The right ventricle in HFpEF-PH was less dilated and hypertrophied than in PAH. In addition, RV ejection fraction was more preserved (HFpEF-PH: 52 +/- 11 versus PAH: 36 +/- 12%). RV filling patterns differed: vena cava backflow during RA contraction was observed in PAH only. In HFpEF-PH, RA pressure was elevated throughout the cardiac cycle (HFpEF-PH: 10 [8-14] versus PAH: 7 [5-10] mm Hg), while RA volume was smaller, reflecting excessive RA stiffness (HFpEF-PH: 0.14 [0.10-0.17] versus PAH: 0.08 [0.06-0.11] mm Hg/mL). RA stiffness was associated with an increased eccentricity index (HFpEF-PH: 1.3 +/- 0.2 versus PAH: 1.2 +/- 0.1) and interatrial pressure gradient (9 [5 to 12] versus 2 [-2 to 5] mm Hg). Conclusions: RV/RA function was less compromised in HFpEF-PH than in PAH, despite similar pressure-overload. Increased RA pressure and stiffness in HFpEF-PH were explained by left atrial/RA-interaction. Therefore, our results indicate that increased RA pressure is not a sign of overt RV failure but rather a reflection of HFpEF-severity

Right Ventricular and Right Atrial Function Are Less Compromised in Pulmonary Hypertension Secondary to Heart Failure With Preserved Ejection Fraction: A Comparison With Pulmonary Arterial Hypertension With Similar Pressure Overload

Background: Heart failure with preserved ejection fraction (HFpEF) is a prevalent disorder for which no effective treatment yet exists. Pulmonary hypertension (PH) and right atrial (RA) and ventricular (RV) dysfunction are frequently observed. The question remains whether the PH with the associated RV/RA dysfunction in HFpEF are markers of disease severity. Methods: To obtain insight in the relative importance of pressure-overload and left-to-right interaction, we compared RA and RV function in 3 groups: 1. HFpEF (n=13); 2. HFpEF-PH (n=33), and; 3. pulmonary arterial hypertension (PAH) matched to pulmonary artery pressures of HFpEF-PH (PH limited to mPAP >= 30 and <= 50 mmHg) (n=47). Patients underwent right heart catheterization and cardiac magnetic resonance imaging. Results: The right ventricle in HFpEF-PH was less dilated and hypertrophied than in PAH. In addition, RV ejection fraction was more preserved (HFpEF-PH: 52 +/- 11 versus PAH: 36 +/- 12%). RV filling patterns differed: vena cava backflow during RA contraction was observed in PAH only. In HFpEF-PH, RA pressure was elevated throughout the cardiac cycle (HFpEF-PH: 10 [8-14] versus PAH: 7 [5-10] mm Hg), while RA volume was smaller, reflecting excessive RA stiffness (HFpEF-PH: 0.14 [0.10-0.17] versus PAH: 0.08 [0.06-0.11] mm Hg/mL). RA stiffness was associated with an increased eccentricity index (HFpEF-PH: 1.3 +/- 0.2 versus PAH: 1.2 +/- 0.1) and interatrial pressure gradient (9 [5 to 12] versus 2 [-2 to 5] mm Hg). Conclusions: RV/RA function was less compromised in HFpEF-PH than in PAH, despite similar pressure-overload. Increased RA pressure and stiffness in HFpEF-PH were explained by left atrial/RA-interaction. Therefore, our results indicate that increased RA pressure is not a sign of overt RV failure but rather a reflection of HFpEF-severity.Therapeutic cell differentiatio