The oxygen carrier M101 alleviates complement activation, which may be beneficial for donor organ preservation

Abstract

During organ transplantation, ischemia/reperfusion injury and pre-formed anti-HLA antibodies are the main cause of delayed graft function and recovery through the activation of the complement system. By supplying oxygen during transplantation, M101 is suspected to avoid complement activation, however, a direct effect exerted by M101 on this pathway is unknown. This was tested by using functional assays (lymphocytotoxic crossmatch test, C3d Luminex-based assay, 50% complement hemolysis [CH50], and 50% alternative complement pathway [AP50/AH50]), and quantitative assays (C3, C3a, C4, C5, C5a, C6, C7, C8, C9 and sC5b-9). M101 interferes with the anti-HLA lymphocytotoxic crossmatch assay, and this effect is complement-dependent as M101 inhibits the classical complement pathway (CH50) in a dose-dependent and stable manner. Such inhibition was independent from a proteolytic effect (fractions C3 to C9) but related to a dose-dependent inhibition of the C3 convertase as demonstrated by exploring downstream the release of the anaphylatoxins (C3a and C5a), C3d, and sC5b-9. The C3 convertase inhibition in the presence of M101 was further demonstrated in the AP50/AH50 assay. In conclusion, the use of M101 avoids the activation of the complement pathway, which constitutes an additional advantage for this extracellular hemoglobin to preserve grafts from ischemia/reperfusion injury and preformed anti-HLA antibodies.

Urinary soluble CD163 is useful as “liquid biopsy” marker in lupus nephritis at both diagnosis and follow-up to predict impending flares

“…The immunological panel for SLE-associated biomarkers included: (i) the complement fractions C3, C4 (Cobas 500 ® , Roche Diagnostics GmBH, Germany) and 50 % concentration haemolytic (CH50; SpaPlus ® , The Binding Site, Birmingham, UK); (ii) IgG anti-double stranded (ds)DNA and anti-chromatin Abs (Bioplex ® , Biorad, Hercules, CA); (iii) IgG anti-extractable nuclear (ENA) Abs against sicca syndrome (SS)A 52 kDa, SSA 60 kDa, SSB, Smith (Sm), Sm-ribonucleoprotein (RNP), RNP A, and RNP 68 kDa antigens (Bioplex ® ); (iv) IgG anti-ribosomal Abs (Bioplex ® ); (v) IgG anti-C1q Abs (Quanta-lite ® , Werfen, Barcellona, Spain); and (vi) the spot urinary sCD163 (ELLA ® , Bio-techne, Minneapolis, MN) that was evaluated together with proteinuria and creatinuria (Cobas 500 ® ) in order to express sCD163 as a ratio to creatinuria, proteinuria, or not as well as the ratio of urine protein excretion to creatinine or PCR [ [22] , [23] , [24] , [25] , [26] ]. Cut-offs were fixed as recommended by the providers (C3 low <0.72 g/L; C4 low <0.11 g/L, CH50 low <31 %; anti-dsDNA Abs ≥10 international units [IU]/mL, anti-ENA/-Ribosomal/-Chromatin Abs ≥1.0 arbitrary units [AU]mL, and anti-C1q Abs ≥20 AU/mL) with the exception of the normalized urinary sCD163/creatinuria ratio as no consensus existed.…”

Oxygen carriers affect kidney immunogenicity during ex-vivo machine perfusion

“…Hence, alternative OCs have been developed as urgently awaited RBC replacement approach. In addition, those OCs usually exhibit beneficial features such as higher oxygen- and carbon dioxide-carrying capacity and a lower antigenicity ( 13 , 14 ).…”

“…M101 was associated with higher ATP levels, indicating improved mitochondrial function, reduced oxidative stress levels, lower pro-inflammatory immune responses, and attenuated ischemia-reperfusion injuries ( 21 ). In addition, a recent study showed that M101 indirectly alleviates the complement activation by reducing ischemia-reperfusion injuries ( 14 ).…”

Effects of M101—an Extracellular Hemoglobin—applied During Cardiopulmonary Resuscitation: An Experimental Rodent Study

“…Animal studies showed that M101 does not bind NO (nitric oxide), nor causes vasoconstriction, and has no immunogenicity, compared with other noncell-bound hemoglobin carriers (15–17). Studies in mice demonstrated an increase in the oxygenation of poorly vascularized tissues (18).…”

“…Animal studies showed that M101 does not bind NO (nitric oxide), nor causes vasoconstriction, and has no immunogenicity, compared with other noncell-bound hemoglobin carriers (15)(16)(17).…”