IMPORTANZA CLINICA DELLA TIPIZZAZIONE SIEROLOGICA E MOLECOLARE DELLE VARIANTI DELL'ANTIGENE RhD

Il sistema Rh, dopo quello ABO, è il sistema gruppo-ematico eritrocitario più immunogeno dell’uomo. Infatti all’esecuzione del gruppo ABO si accompagna sistematicamente la contemporanea determinazione del fenotipo Rh. L’antigene più importante del sistema Rh, l’antigene D, è molto più efficace di qualunque altro antigene eritrocitario nel determinare una risposta anticorpale quando venga introdotto in un soggetto che ne è privo. Esso è presente sugli eritrociti dell’85% delle persone di razza bianca ed in percentuale ancora più alta in quelle di razza nera . Quindi dopo gli antigeni A e B, il D è il più importante nella pratica trasfusionale. Diversamente dagli antigeni A e B, tuttavia, le persone che non possiedono l’antigene D sui propri eritrociti non presentano, regolarmente, l’anti-D. La formazione dell’anticorpo anti-D origina dall’esposizione, per motivi trasfusionali o gravidanze, ad emazie che presentano l’antigene D. E’ stato stimato che dal 30 all’85% delle persone D negative che ricevono una trasfusione D positiva svilupperà l’anti-D. Per questo motivo, tutti i riceventi e tutti i donatori di sangue vengono esaminati, nelle procedure di routine, per la presenza dell’antigene D, al fine di assicurare che i riceventi D negativi vengano identificati e ricevano sangue D negativo. L’antigene D è stato da sempre oggetto di studio dell’immunoematologia. L’interesse verso tale antigene è aumentato dopo la scoperta che alcuni individui RhD positivi producevano in seguito a trasfusioni anticorpi anti-D. Successivi studi portarono alla scoperta del mosaicismo dell’antigene RhD e rivelarono la sua grande variabilità (D partial e D weak). In passato, i limiti delle metodiche sierologiche non consentirono di identificare le molte varianti dell’antigene D, che perciò venivano identificate come D negativo. Questo non rappresentava un problema nell’individuo ricevente la trasfusione, dato che veniva trasfuso con sangue RhD negativo (come riceventi alcune varianti sono tutt’ora trattate come RhD negative), ma creava un problema se l’individuo era un donatore di sangue, in quanto i soggetti D variant, possono determinare nel ricevente RhD negativo la produzione di alloanticorpi . La corretta identificazione delle varianti dell’antigene RhD è fondamentale anche per le donne gravide RhD negative, in quanto vanno sottoposte ad immunoprofilassi se il neonato è un D variant e quindi può stimolare la produzione di anticorpi che potrebbero causare una malattia emolitica del neonato (MEN) in una successiva gravidanza con feto RhD positivo. Nei servizi trasfusionali (SIT) nasce quindi l’esigenza di dover correttamente tipizzare individui che, dai test sierologici, risultano negativi, in modo da determinare possibili D variant per evitare alloimmunizzazioni da trasfusione e programmare immunoprofilassi MEN nelle donne gravide quando richiesto

Features, Causes and Consequences of Splanchnic Sequestration of Amino Acid in Old Rats

RATIONALE: In elderly subjects, splanchnic extraction of amino acids (AA) increases during meals in a process known as splanchnic sequestration of amino acids (SSAA). This process potentially contributes to the age-related progressive decline in muscle mass via reduced peripheral availability of dietary AA. SSAA mechanisms are unknown but may involve an increased net utilization of ingested AA in the splanchnic area. OBJECTIVES: Using stable isotope methodology in fed adult and old rats to provide insight into age-related SSAA using three hypotheses: 1) an increase in protein synthesis in the gut and/or the liver, 2) an increase in AA oxidation related to an increased ureagenesis, and 3) Kupffer cell (KC) activation consequently to age-related low-grade inflammation. FINDINGS: Splanchnic extraction of Leu (SPELeu) was doubled in old rats compared to adult rats and was not changed after KC inactivation. No age-related effects on gut and liver protein synthesis were observed, but urea synthesis was lower in old rats and negatively correlated to liver Arg utilization. Net whole-body protein synthesis and arterial AA levels were lower in old rats and correlated negatively with SPELeu. CONCLUSION: SSAA is not the consequence of age-related alterations in ureagenesis, gut or liver protein synthesis or of KC activity. However, SSAA may be related to reduced net whole-body protein synthesis and consequently to the reduced lean body mass that occurs during aging

Kupffer Cells Hasten Resolution of Liver Immunopathology in Mouse Models of Viral Hepatitis

Kupffer cells (KCs) are widely considered important contributors to liver injury during viral hepatitis due to their pro-inflammatory activity. Herein we utilized hepatitis B virus (HBV)-replication competent transgenic mice and wild-type mice infected with a hepatotropic adenovirus to demonstrate that KCs do not directly induce hepatocellular injury nor do they affect the pathogenic potential of virus-specific CD8 T cells. Instead, KCs limit the severity of liver immunopathology. Mechanistically, our results are most compatible with the hypothesis that KCs contain liver immunopathology by removing apoptotic hepatocytes in a manner largely dependent on scavenger receptors. Apoptotic hepatocytes not readily removed by KCs become secondarily necrotic and release high-mobility group box 1 (HMGB-1) protein, promoting organ infiltration by inflammatory cells, particularly neutrophils. Overall, these results indicate that KCs resolve rather than worsen liver immunopathology

M2 microglia and macrophages drive oligodendrocyte differentiation during CNS remyelination

The lack of therapies for progressive multiple sclerosis highlights the need to understand the regenerative process of remyelination that can follow CNS demyelination. This involves an innate immune response consisting of microglia/macrophages, which can be polarized to distinct functional phenotypes: proinflammatory (M1) or anti-inflammatory/immunoregulatory (M2). Here we show that a switch from an M1- to M2-dominant response occurred within microglia and peripherally-derived macrophages as remyelination started. Oligodendrocyte differentiation was enhanced in vitro with M2 conditioned media, and impaired in vivo following intra-lesional M2 depletion. M2 densities were increased in lesions of aged mice in which remyelination was enhanced by parabiotic coupling to a younger animal, and in MS lesions that normally show remyelination. Blocking M2-derived activin-A inhibited oligodendrocyte differentiation during remyelination in cerebellar slice cultures. Our results therefore show that M2 polarization is essential for efficient remyelination and identify activin-A as a novel therapeutic target for CNS regeneration

Oval Cell Response Is Attenuated by Depletion of Liver Resident Macrophages in the 2-AAF/Partial Hepatectomy Rat

BACKGROUND/AIMS: Macrophages are known to play an important role in hepatocyte mediated liver regeneration by secreting inflammatory mediators. However, there is little information available on the role of resident macrophages in oval cell mediated liver regeneration. In the present study we aimed to investigate the role of macrophages in oval cell expansion induced by 2-acetylaminofluorene/partial hepatectomy (2-AAF/PH) in rats. METHODOLOGY/PRINCIPAL FINDINGS: We depleted macrophages in the liver of 2-AAF/PH treated rats by injecting liposome encapsulated clodronate 48 hours before PH. Regeneration of remnant liver mass, as well as proliferation and differentiation of oval cells were measured. We found that macrophage-depleted rats suffered higher mortality and liver transaminase levels. We also showed that depletion of macrophages yielded a significant decrease of EPCAM and PCK positive oval cells in immunohistochemical stained liver sections 9 days after PH. Meanwhile, oval cell differentiation was also attenuated as a result of macrophage depletion, as large foci of small basophilic hepatocytes were observed by day 9 following hepatectomy in control rats whereas they were almost absent in macrophage depleted rats. Accordingly, real-time polymerase chain reaction analysis showed lower expression of albumin mRNA in macrophage depleted livers. Then we assessed whether macrophage depletion may affect hepatic production of stimulating cytokines for liver regeneration. We showed that macrophage-depletion significantly inhibited hepatic expression of tumor necrosis factor-α and interleukin-6, along with a lack of signal transducer and activator of transcription 3 phosphorylation during the early period following hepatectomy. CONCLUSIONS: These data indicate that macrophages play an important role in oval cell mediated liver regeneration in the 2-AAF/PH model