Genetic methods of antibody generation and their use in immunohistochemistry.

Genetic methods of antibody generation offer a highly tuneable tool for the production of target specific reagents suitable for a wide range of applications, including immunohistochemistry. The direct linkage between binder phenotype and genotype enables the rapid identification and manipulation of specific binders into formats suitable for highly specific and sensitive detection of targets from soluble proteins to individual components of multi-protein structures within the context of living tissues. Here we review the types of genetic methods employed and binder formats available and demonstrate how mining huge combinatorial repertoires of binders can deliver diverse and exquisitely sensitive tools for the use in immunohistochemistry. Finally, we offer a perspective on how this approach might be further refined to routinely deliver binders for specific use in immunohistochemical studies.

The impact of organ dysfunction in cirrhosis: survival at a cost?

BACKGROUND & AIMS: The incidence of cirrhosis and subsequent development of organ dysfunction (OD) requiring intensive care unit (ICU) support is rising. Historically, critically ill cirrhotics are perceived as having poor prognosis and substantial cost of care. METHODS: The aim was to prospectively analyse resource utilisation and cost of a large cohort of patients (n=660) admitted to a Liver ICU from 2000 to 2007 with cirrhosis and OD. Child Pugh, MELD, SOFA, APACHE II, and organ support requirements were collected. The Therapeutic Intervention Scoring System (TISS) score, a validated tool for estimating cost in ICU, was calculated daily. Logistic regression was used to determine independent predictors of increased cost. RESULTS: Alcohol was the most common etiology (47%) and variceal bleeding (VB) the most common reason for admission (35%). Invasive ventilatory support was required in 74% of cases, vasopressors in 49%, and 50% required renal replacement therapy. Forty-nine per cent of non-transplanted patients survived to ICU discharge. Median TISS score and ICU cost per patient were 261 and €14,139, respectively. VB patients had the highest survival rates (53% vs. 24%; p<0.001) and lower associated cost. A combination of VB (OR 0.48), need for ventilation (OR 2.81), low PO(2)/FiO(2) on admission (OR 0.97), and lactate (OR 0.93) improved cost prediction on multivariate analysis (AUROC 0.7; p<0.001) but organ failure scores per se were poor predictors of cost. CONCLUSIONS: Patients with cirrhosis and OD result in considerable resource expenditure but have acceptable hospital survival. Further health economic assessment and outcome prediction tools are required to appropriately target resource utilisation.

Safety and efficacy of combined use of sildenafil, bosentan, and iloprost before and after liver transplantation in severe portopulmonary hypertension.

Portopulmonary hypertension (PPHTN) represents a constrictive pulmonary vasculopathy in patients with portal hypertension. Liver transplantation (LT) may be curative and is usually restricted to patients with mild-to-moderate disease severity characterized by a mean pulmonary artery pressure (mPAP < 35 mm Hg). Patients with severe disease (mPAP > 50 mm Hg) are usually excluded from transplantation. We describe a patient with severe PPHTN, initiated on sequential and ultimately combination therapy of prostacyclin, sildenafil, and bosentan (PSB) pretransplantation and continued for 2 years posttransplantation. Peak mPAP on PSB therapy was dramatically reduced from 70 mm Hg to 32 mm Hg pretransplantation, and continued therapy facilitated a further fall in mPAP to 28 mm Hg posttransplantation. The pulmonary vascular resistance index fell from 604 to 291 dyne second(-1) cm(-5). The perioperative mPAP rose to 100 mm Hg following an episode of sepsis and fell with optimization of PSB therapy. In conclusion, this is the first reported patient with severe PPHTN using this combination of vasodilator therapy as a bridge to LT and then as maintenance in the posttransplantation phase. This regimen may enable LT in similar patients in the future, without long-term consequences.

A comparison of the ability of the human IgG1 allotypes G1m3 and G1m1,17 to stimulate T-cell responses from allotype matched and mismatched donors.

The immunogenicity of clinically administered antibodies has clinical implications for the patients receiving them, ranging from mild consequences, such as increased clearance of the drug from the circulation, to life-threatening effects. The emergence of methods to engineer variable regions resulting in the generation of humanised and fully human antibodies as therapeutics has reduced the potential for adverse immunogenicity. However, due to differences in sequence referred to as allotypic variation, antibody constant regions are not homogeneous within the human population, even within sub-classes of the same immunoglobulin isotype. For therapeutically administered antibodies, the potential exists for an immune response from the patient to the antibody if the allotype of patient and antibody do not match. Allotypic distribution in the human population varies within and across ethnic groups making the choice of allotype for a therapeutic antibody difficult. This study investigated the potential of human IgG1 allotypes to stimulate responses in human CD4(+) T cells from donors matched for homologous and heterologous IgG1 allotypes. Allotypic variants of the therapeutic monoclonal antibody trastuzumab were administered to genetically defined allotypic matched and mismatched donor T cells. No significant responses were observed in the mismatched T cells. To investigate the lack of T-cell responses in relation to mismatched allotypes, HLA-DR agretopes were identified via MHC associated peptide proteomics (MAPPs). As expected, many HLA-DR restricted peptides were presented. However, there were no peptides presented from the sequence regions containing the allotypic variations. Taken together, the results from the T-cell assay and MAPPs assay indicate that the allotypic differences in human IgG1 do not represent a significant risk for induction of immunogenicity.

Outcome of patients with cirrhosis admitted to intensive care.

PURPOSE OF REVIEW: The incidence of cirrhosis is increasing exponentially and is associated with significant morbidity and mortality. This cirrhotic population is prone to infection, which is a frequent precipitant for the development of organ dysfunction; a syndrome often referred to as 'acute-on-chronic' liver failure. Historically, the perception of cirrhosis with organ dysfunction as having a poor prognosis has led to invariably iniquitous access to intensive care. Data to support this view, however, are lacking. RECENT FINDINGS: Acute variceal bleeding is associated with markedly improved survival and warrants organ support in intensive care. Survival correlates directly with the number of organs failing, with sepsis and multiorgan failure resulting in over 90% mortality. The requirement for renal replacement therapy confers a poor prognosis in patients not suitable for liver transplantation. SUMMARY: Admission to intensive care for many patients with cirrhosis is not futile, particularly for those with single organ dysfunction and acute variceal bleeding. It can be extremely challenging to manage patients with organ dysfunction and encephalopathy in a ward environment, and these patients frequently require, and indeed benefit from, augmented levels of care in high-dependency and intensive care environments.

Regulatory role of SGT1 in early R gene-mediated plant defenses.

Animal SGT1 is a component of Skp1-Cullin-F-box protein (SCF) ubiquitin ligases that target regulatory proteins for degradation. Mutations in one (SGT1b) of two highly homologous Arabidopsis SGT1 genes disable early plant defenses conferred by multiple resistance (R) genes. Loss of SGT1b function in resistance is not compensated for by SGT1a. R genes differ in their requirements for SGT1b and a second resistance signaling gene, RAR1, that was previously implicated as an SGT1 interactor. Moreover, SGT1b and RAR1 contribute additively to RPP5-mediated pathogen recognition. These data imply both operationally distinct and cooperative functions of SGT1 and RAR1 in plant disease resistance.

Arabidopsis RAR1 exerts rate-limiting control of R gene-mediated defenses against multiple pathogens.

We have identified the Arabidopsis ortholog of barley RAR1 as a component of resistance specified by multiple nucleotide binding/Leu-rich repeat resistance (R) genes recognizing different bacterial and oomycete pathogen isolates. Characterization of partially and fully defective rar1 mutations revealed that wild-type RAR1 acts as a rate-limiting regulator of early R gene-triggered defenses, determining the extent of pathogen containment, hypersensitive plant cell death, and an oxidative burst at primary infection sites. We conclude that RAR1 defense signaling function is conserved between plant species that are separated evolutionarily by 150 million years. RAR1 encodes a protein with two zinc binding (CHORD) domains that are highly conserved across eukaryotic phyla, and the single nematode CHORD-containing homolog, Chp, was found previously to be essential for embryo viability. An absence of obvious developmental defects in null Arabidopsis rar1 mutants favors the notion that, in contrast, RAR1 does not play a fundamental role in plant development.