William A. Sewell

Clinical uses of intravenous immunoglobulin

There has been a rapid expansion in the use of intravenous immunoglobulin (IVIG) for an ever growing number of conditions. It is a product with an excellent safety record without the side effects of steroids or other immunosuppressive agents. There have been numerous recent advances in our understanding of the mechanisms of action of IVIG in many of the conditions for which it is being used, but there is still much to be learned. IVIG has had a major impact in neurology, haematology, immunology, rheumatology and dermatology. The limitations for IVIG are cost of the preparation itself and the logistical problems associated with its administration. Many of the side effects are managed easily by careful screening of the patient prior to treatment, premedication with analgesics and antihistamines and adjustment of infusion rate. It is likely, however, that side effects will be more frequent as the dose given increases and effects on plasma viscosity become greater [122]. It will be important to increase the evidence base for IVIG in many conditions to define its therapeutic role. In addition, there have been very few dose-ranging studies for hdIVIG and fewer still of which adjunctive agents (including biological agents such as rituximab and daclizumab) might offer the best therapeutic combinations. Although not established, the use of IVIG is being studied in a range of conditions including heart failure, mycobacterial infection, adult respiratory distress syndrome, transplantation, fibrosis, connective tissue disease, encephalitis, epilepsy and even Alzheimers disease. Should IVIG prove to be of efficacy in these settings it is likely to have major implications for drug budgets as many of the conditions are very common and place great strain on the worlds supply of IVIG itself. Future studies will therefore need to address questions of efficacy, pharmacoeconomics, dose, adjunctive therapies and mechanism of action which may point the way to novel treatment strategies beyond IVIG. It is also clear, however, that controlled trials in many of the rare conditions may be very difficult to carry out and approaches such as prospective disease registries may be needed.

Immunomodulatory action of intravenous immunoglobulin

Intravenous immunoglobulin (IVIg) is a blood product prepared from the serum of between 1000 and 15 000 donors per batch. It is the treatment of choice for patients with antibody deficiencies. In this indication, IVIg is used at a ‘replacement dose’ of 200–400 mg/kg body weight, given approximately 3-weekly. In contrast, ‘high-dose’ IVIg (hdIVIg), given most frequently at 2 g/kg/month, is used as an ‘immunomodulatory’ agent in an increasing number of immune and inflammatory disorders. Initial use of hdIVIg was for idiopathic thrombocytopenic purpura (ITP) in children.1 Despite a lack of double-blind, randomized, placebo-controlled trials, many other conditions are managed with hdIVIg, including numerous haematological, rheumatological, neurological and dermatological disorders.2 In this article, we review the current understanding and recent developments in the immunomodulatory mechanisms of action of hdIVIg. IVIg may, for the purposes of clarity, be considered to have four separate mechanistic components: (1) actions mediated by the variable regions F(ab′)2, (2) actions of Fc on a range of Fc receptors (FcR), (3) actions mediated by complement binding within the Fc fragment, and (4) immunomodulatory substances other than antibody in the IVIg preparations (Fig. 1). It is likely that these components act concurrently, however, different mechanisms may be important in different settings. We will address the mechanisms under these broad headings although in some cases more than one mechanism is operative or our understanding does not allow accurate categorization. Figure 1 Immunomodulatory actions of intravenous immunoglobulin. Intravenous immunoglobulin (IVIg) may for the purposes of understanding be thought of as four separate components: (1) actions mediated by the variable regions F(ab′)2, (2) actions of Fc ... F(ab′)2 Mediating Binding Site Interactions of IVIg Anti-proliferative effects IVIg has been shown to have a considerable inhibitory effect on mitogen-induced T-cell proliferation in vitro.3 This effect has been shown for intact immunoglobulin G (IgG), with less evidence for a role for Fc fragment.4 Single-donor preparations of IVIg inhibited proliferation more than commercial multiple-donor preparations, but there was no difference between standard IVIg preparations and cytomegalovirus hyperimmune globulin.4 Both antigen-dependent and antigen-independent responses are inhibited by IVIg in a dose-dependent manner.5 T-cell proliferation in response to anti-CD3 or tetanus toxoid was shown to be inhibited by IVIg in a dose-dependent manner over a range of IgG concentrations (0–10 mg/ml).6 The inhibition was reversible by exogenous interleukin-2 (IL-2) and the authors concluded that the effects were a result of interference with cytokine-mediated T-cell proliferation. Both pooled normal human immunoglobulin, and single donor immunoglobulin were shown to reduce pokeweed mitogen (PWM) -induced plaque-forming cell formation following 300 mg/kg infusions into patients with common variable immunodeficiency.7 This effect was short-lived, and sera collected >24 hr post-infusion no longer inhibited cell proliferation. The suppressive effects of IVIg when used at replacement dose (100–200 mg/kg) were demonstrated in antibody-deficient children.8 In this study, the effects of the childrens sera on the immunoglobulin-producing activity of PWM-stimulated normal lymphocytes was assessed. Even this low-dose IVIg was shown to enhance the suppressive activity of the patients lymphocytes, an effect that was reversed on cessation of IVIg therapy.

The structure of the human CD2 gene and its expression in transgenic mice.

We report the genomic organization of the human CD2 gene and its expression in transgenic mice. A 28.5 kb segment of DNA consisting of 4.5 kb 5′ flanking sequences, 15 kb containing the genes five exons and 9 kb of 3′ flanking sequences can direct the expression of the CD2 gene only on thymocytes, circulating T cells and megakaryocytes of the transgenic mice. The expression of each copy of the human CD2 transgene appears to be as high as the endogenous mouse CD2 gene and as high as the expression on the surface of human T lymphocytes, independent of the site of integration and dependent on the copy number of genes that have integrated.

Chronic cough resembles asthma with IL-5 and granulocyte-macrophage colony-stimulating factor gene expression in bronchoalveolar cells ☆ ☆☆ ★ ★★

BACKGROUND Chronic cough is a multifactorial condition, which, like asthma, can be associated with eosinophilic airway inflammation. In asthma, airway eosinophilia is believed to be mediated by cytokines such as interleukin-5 and granulocyte-macrophage colony stimulating factor (GM-CSF). The role of these cytokines in chronic cough is unclear. OBJECTIVE The aim of this study was to examine gene expression for IL-5 and GM-CSF in chronic cough and compare the results with those found in asthma. METHODS We studied adults with asthma (n = 12), chronic cough responsive to inhaled corticosteroid (ICS-responsive cough) (n = 9), and chronic cough not responsive to inhaled corticosteroid (non-ICS-responsive cough) (n = 4). Bronchoalveolar lavage (BAL) was performed, and cytokine gene expression was assessed by using a semiquantitative reverse transcriptase polymerase chain reaction. RESULTS IL-5 mRNA was expressed by BAL cells from nine of 12 asthmatic subjects and six of nine subjects with ICS-responsive chronic cough. IL-5 mRNA was not detected in subjects with non-ICS-responsive chronic cough (zero of four subjects, p < 0.05). GM-CSF mRNA was expressed in BAL cells from seven of 12 asthmatic subjects and six of nine subjects with ICS-responsive cough. GM-CSF mRNA was not detected in non-ICS responsive cough subjects (zero of four subjects, p < 0.05). GM-CSF gene expression was related to the degree of methacholine airway responsiveness in asthmatic subjects (r = -0.59). CONCLUSION We conclude that chronic cough, like asthma, is associated with airway inflammation and gene expression for IL-5 and GM-CSF. Ongoing expression of these cytokines is likely to be related to the persistence of airway inflammation and chronic cough.

Secretion of electrolytes by the pancreas of the anaestetized rat.

1. HCO‐3, Na+ and K+ concentrations were measured in bile‐free pancreatic juice collected from fasted and fed anaesthetized rats. 2. Resting flow rates averaged 0.62 mul. g‐1 .min‐1 (fasted) and 2.8 mul. g‐1. min‐1 (fed) and the mean HCO‐3 concentrations, respectively, were 25.8 and 33.3 mM. 3. In fasted rats, instillation of HCl into the duodenum caused flow rate to increase threefold and HCO‐3 concentrations to double (66 mM). Intravenous infusion of pure natural (GIH) secretin caused a fivefold increase in flow rate; HCO‐3 concentrations, again, doubled (67.5 mM). Infusion of synthetic secretin produced effects essentially the same as those produced by GIH secretin. 4. Infusion of Boots secretin caused a thirteenfold increase in flow rate (8.32 mul.g‐1. min‐1) but HCO‐3 concentrations rose only slightly (43.3 mM). However, following cessation of infusion, when flow rate approximated the maximum obtained with pure secretin, the HCO‐3 concentration was much higher (57.2 mM at 3.19 uml.g‐1.min‐1). In fed animals the responses were similar but maximum flow rates were greater (12 mul. g‐1. min‐1). 5. Infusion of caerulein produced a secretory rate slightly less than with Boots secretin (5.06 mul. g‐1.min‐1) and HCO‐3 concentrations were plasmalike (30.2 mM); infusion of the synthetic octapeptide of cholecystokinin (OP‐CCK) gave similar flow rates and HCO‐3 concentrations. 6. Infusion of a mixture of caerulein and GIH secretin mimicked closely the effect of Boots secretin. At maximum flow rates (7.6 mul. g‐1. min‐1) the HCO‐3 concentration was 43.7 mM and at lower flow rates (3.90 mul.g‐1. min‐1) it rose to 54.2mM. 7. It is concluded that the response of the rat pancreas to secretin is qualitatively similar to that of all other vertebrates so far studied, but, relative to other animals, the response is sluggish. In contrast, the rat pancreas responds well to cholecystokinin (CCK) stimulation, yielding a juice with plasma‐like HCO‐3 concentration. Boots secretin, which is heavily contaminated with CCK, causes a mixed response resembling that of CCK at high secretory rates and that of pure secretin at lower rates. 8. An unexplained feature of rat pancreatic juice was that K+ concentrations, although plasma‐like in unstimulated samples, rose to about 8mM when flow rate increases as a result of secretin, but not CCK, stimulation. In all other animals so far studied, the K+ concentration has been found to be independent of flow rate.

Group 2 innate lymphoid cells (ILC2s) are increased in chronic rhinosinusitis with nasal polyps or eosinophilia

Chronic rhinosinusitis (CRS) is a heterogeneous disease with an uncertain pathogenesis. Group 2 innate lymphoid cells (ILC2s) represent a recently discovered cell population which has been implicated in driving Th2 inflammation in CRS; however, their relationship with clinical disease characteristics has yet to be investigated.

Analysis of human leukaemias and lymphomas using extensive immunophenotypes from an antibody microarray

A novel antibody microarray has been developed that provides an extensive immunophenotype of leukaemia cells. The assay is a solid phase cell‐capture technique in which 82 antigens are studied simultaneously. This paper presents the analysis of 733 patients with a variety of leukaemias and lymphomas from peripheral blood and bone marrow. Discriminant Function Analysis of the expression profiles from these 733 patients and 63 normal subjects were clustered and showed high levels of consistency with diagnoses obtained using conventional clinical and laboratory criteria. The overall levels of consensus for classification using the microarray compared with established criteria were 93·9% (495/527 patients) for peripheral blood and 97·6% (201/206 patients) for bone marrow aspirates, showing that the extensive phenotype alone was frequently able to classify the disease when the leukaemic clone was the dominant cell population present. Immunophenotypes for neoplastic cells were distinguishable from normal cells when the leukaemic cell count was at least 5 × 109 cells/l in peripheral blood, or 20% of cells obtained from bone marrow aspirates. This technique may be a useful adjunct to flow cytometry and other methods when an extensive phenotype of the leukaemia cell is desired for clinical trials, research and prognostic factor analysis.

Bench-to-bedside review: Immunoglobulin therapy for sepsis - biological plausibility from a critical care perspective

Sepsis represents a dysregulated host response to infection, the extent of which determines the severity of organ dysfunction and subsequent outcome. All trialled immunomodulatory strategies to date have resulted in either outright failure or inconsistent degrees of success. Intravenous immunoglobulin (IVIg) therapy falls into the latter category with opinion still divided as to its utility. This article provides a narrative review of the biological rationale for using IVIg in sepsis. A literature search was conducted using the PubMed database (1966 to February 2011). The strategy included the following text terms and combinations of these: IVIg, intravenous immune globulin, intravenous immunoglobulin, immunoglobulin, immunoglobulin therapy, pentaglobin, sepsis, inflammation, immune modulation, apoptosis. Preclinical and extrapolated clinical data of IVIg therapy in sepsis suggests improved bacterial clearance, inhibitory effects upon upstream mediators of the host response (for example, the nuclear factor kappa B (NF-κB) transcription factor), scavenging of downstream inflammatory mediators (for example, cytokines), direct anti-inflammatory effects mediated via Fcγ receptors, and a potential ability to attenuate lymphocyte apoptosis and thus sepsis-related immunosuppression. Characterizing the trajectory of change in immunoglobulin levels during sepsis, understanding mechanisms contributing to these changes, and undertaking IVIg dose-finding studies should be performed prior to further large-scale interventional trials to enhance the likelihood of a successful outcome.

Increased expression of interferon‐gamma in hyperplastic lymph nodes from HIV‐infected patients

Polyclonal B cell activation is characteristic of HIV infection and occurs in the presence of severe CD4+ lymphocyte depletion. In contrast, CD4+ lymphocytes are the dominant T cell in the reactive lymphoid tissues of patients not infected with HIV. In this study, lymph node biopsies from eight HIV‐infectcd patients with persistent generalized lymphadenopathy syndrome (PGL) were assessed for IL‐lβ, IL‐2, IL‐4, IL‐6, IL‐10, interferon‐gamma (IFN‐γ) and tumour necrosis factor‐beta (TNF‐β) gene expression using the polymerase chain reaction (PCR). The cytokine gene expression of two cases of reactive adenopathy in patients not infected with HIV was assessed for comparison. IFN‐γ was expressed much more strongly in the PGL samples than in control reactive lymphoid tissues, whereas the other cytokines were expressed to a similar extent in both types of tissues. IFN‐γ may have an important role in maintaining the adenopalhy of HIV‐infected patients. Expression of cytokines such as IL‐2, IL‐4 and IL‐10 in HIV nodes may be adequate to allow the recruitment of naive B cells to the reactive process.

Many human immunoglobulin heavy-chain IGHV gene polymorphisms have been reported in error

The identification of the genes that make up rearranged immunoglobulin genes is critical to many studies. For example, the enumeration of mutations in immunoglobulin genes is important for the prognosis of chronic lymphocytic leukemia, and this requires the accurate identification of the germline genes from which a particular sequence is derived. The immunoglobulin heavy‐chain variable (IGHV) gene repertoire is generally considered to be highly polymorphic. In this report, we describe a bioinformatic analysis of germline and rearranged immunoglobulin gene sequences which casts doubt on the existence of a substantial proportion of reported germline polymorphisms. We report a five‐level classification system for IGHV genes, which indicates the likelihood that the genes have been reported accurately. The classification scheme also reflects the likelihood that germline genes could be incorrectly identified in mutated VDJ rearrangements, because of similarities to other alleles. Of the 226 IGHV alleles that have previously been reported, our analysis suggests that 104 of these alleles almost certainly include sequence errors, and should be removed from the available repertoire. The analysis also highlights the presence of common mismatches, with respect to the germline, in many rearranged heavy‐chain sequences, suggesting the existence of twelve previously unreported alleles. Sequencing of IGHV genes from six individuals in this study confirmed the existence of three of these alleles, which we designate IGHV3‐49*04, IGHV3‐49*05 and IGHV4‐39*07. We therefore present a revised repertoire of expressed IGHV genes, which should substantially improve the accuracy of immunoglobulin gene analysis.