Non-immunological Mechanisms Research Articles

Intestinal Permeability Barrier in Crohn’s Disease: The Difficulty in Shifting the Paradigm

Dr. Daniel Hollander Crohn’s disease has become a relatively common inflammatory disease of the intestine. The etiology of the disease is unknown despite a great deal of research by many talented investigators. During most of the twentieth century, the search for Crohn’s etiology focused mostly on immunological abnormalities. This dominant paradigm hindered the approval of research proposals or manuscripts dealing with other, non-immunological etiological factors or mechanisms. In the early 1980s my research centered on the intestinal transport of lipid compounds, in general, and fat-soluble vitamins in particular [1]. Simultaneously, I was caring for increasing numbers of patients with Crohn’s disease and felt frustrated by the dearth of basic understanding of the etiology of Crohn’s disease and the paucity of available therapeutic approaches. It was known that the disease had a heritable component since it had a clear familial clustering, but the specific genetic abnormalities or predisposing genetic factors were not known. Furthermore, no measurable parameters existed that would enable us to identify the disease in its subclinical phase in the healthy relatives of Crohn’s disease patients. In the early 1980s, I was approached by the father of a patient with Crohn’s who was frustrated by the lack of progress in understanding the pathogenesis of the disease or its effective therapy. He searched the literature regarding Crohn’s and conferred with several investigators, but he was not satisfied with the outcomes of their efforts. He asked if I would be interested in searching for new causes of Crohn’s disease and stated that he was willing to fund a preliminary pilot project through his family foundation to search for new etiological leads [2]. I was aware of three small studies that looked at a newly recognized function of the intestine, namely, the barrier function of the bowel which limits the absorption of D. Hollander (&) Division of Digestive Diseases, UCLA School of Medicine and The Broad Foundation, 10900 Wilshire Blvd, 12th floor, Los Angeles, CA 90024, USA e-mail: dhollander@broadmedical.org; dholland@ucla.edu

Abstract 334: Hypertensive Crisis Combined with Acute Myocardial Ischemic Injury after Glatiramer Acetate Subcutaneous Injection: A Case Presentation and Literature Review

Introduction Hypertensive crisis (HC) affects more than a half million Americans each year, and leave many with irreversible injury. Despite extensive studies on HC and its complications, there remain many unrecognized risk factors and prognosticators. Physicians should perform comprehensive evaluation, including a current medication list review of patients who present with HC to effectively identify the cause and intervene accordingly. We present a case of HC with acute myocardial damage after subcutaneous injection of glatiramer acetate Case presentation A 47 year-old Caucasian male with history of multiple sclerosis (MS) who presented to the emergency room with complaints of headache, chest discomfort, and cough with frothy bloody secretions approximately 30 minutes after subcutaneous injection of glatiramer acetate. For the past 5 years, the patient had reported occasional hot flashes, headache, and palpitations after injection of glatiramer acetate. On examination, blood pressure was 260/160mmHg and heart rate was 120bpm. Chest X-ray showed acute pulmonary edema. EKG showed significant ST elevations in leads I and AVL and ST depressions in leads II, III, and AVF. Troponin levels were elevated during first 24 hours (0.1, 3.7, and 3.5 μg/L). Echocardiography revealed an ejection fraction of 45% with left ventricular wall hypokinesis. Blood pressure was controlled with intravenous nitroprusside and labetalol and after 48hours, repeat EKG was normal, and stress test with myoview was negative for ischemic changes. Discussion Hypertensive crisis is associated with significant morbidity and mortality. Myocardial damage often results from HC and causes subsequent heart failure which leads to death of sufferers. Glatiramer acetate (Copaxone) is an immunomodulator currently used to reduce symptomatic episodes in patients with relapsing-remitting MS. During the post-marketing period, there have been reports of patients with hypertension, chest pain, and others symptoms that received emergency medical care; however, HC combined with acute myocardial damage has been never reported. Whether an immunologic or non-immunologic mechanism mediates these episodes is unknown.

Autoantibodies in Polymyositis and Dermatomyositis

Inflammatory myopathies are a group of acquired diseases, characterized by immunoflogistic processes primarily involving the skeletal muscle. According to recent classification criteria, four major diseases have been identified: polymyositis (PM), dermatomyositis (DM), sporadic inclusion body myositis (IBM), and necrotizing autoimmune myositis (NAM). Autoantibodies can be found in the sera of most patients with myositis. Myositis-specific autoantibodies (MSAs) are markers of very specific disease entities within the spectrum of myositis, and target proteins involved in key processes of protein synthesis. Myositis autoantigens comprise the well-defined aminoacyl-tRNA synthetases, the Mi-2 helicase/histone deacetylase protein complex, and the signal recognition particle (SRP) ribonucleoprotein, together with novel targets such as TIF1-γ, MDA5, NXP2, SAE, and HMGCR. Recent studies suggest that autoantigens drive a B cell antigen-specific immune response in muscles. Interestingly, an increased expression of Jo-1 and Mi-2 in regenerating fibers in muscle biopsies from PM and DM patients compared to normal was demonstrated. Myositis autoantigen up-regulation was observed in neoplastic tissues, thus representing a potential link between cancer and autoimmunity in myositis. Non-immunological mechanisms seem to participate to the pathogenesis of inflammatory myopathies; induction of endoplasmic reticulum stress response in response to abnormal muscle regeneration and inflammation has recently been reported in patients with myositis. This review article provides an update of new emerging insights about the clinical and pathophysiologic role of principal autoantibodies in myositis.

Immune response in a cutaneous allergic drug reaction secondary to imidapril, benazapril and metformin

Introduction: Cutaneous drug reactions may be classified with regard to pathogenesis and clinical morphology. They may be mediated by both immunologic and non-immunologic mechanisms. Case report: A 56 year old female presented with widespread patches and macules, concentrated on her face, trunk and extremities. The lesions were pruritic, and temporally associated with intake of benzapril hydrochloride, imidapril and metformin. Methods: Biopsies for hematoxylin and eosin (H&E) examination, as well as for immunohistochemistry (IHC) and direct immunofluorescence (DIF) analysis were performed for diagnostic purposes, and also to evaluate the lesional immune response. Results: Hematoxylin and eosin staining demonstrated a histologically unremarkable epidermis. Within the dermis, a moderately florid, superficial and deep, perivascular infiltrate of lymphocytes, plasmacytoid lymphocytes, histiocytes and rare eosinophils was identified, consistent with an allergic drug reaction. DIF demonstrated deposits of IgE, Complement/C3 and fibrinogen around dermal blood vessels. IHC demonstrated positive staining with HAM-56 and myeloid/histoid antigen in the cell infiltrate around the upper dermal blood vessels. HLA-ABC was overexpressed around those vessels, as well as around dermal sweat glands. COX-2 demonstrated positive staining in both the epidermis and upper dermis. Conclusion: Drug reactions are significant causes of skin rashes. In the current case, we were able to identify multiple antigen presenting cells in the area of the main inflammatory process. The immunologic case findings suggest that allergic drug eruptions may represent complex processes. An allergic drug reaction should be suspected whenever dermal, perivascular deposits of fibrinogen, Complement/C3 and other markers such as IgE are identified via DIF.

Cells and mediators in diisocyanate-induced occupational asthma

Diisocyanates are the most common cause of occupational asthma in many industrialized countries, and various pathogenic mechanisms have been suggested to be involved. Occupational asthma causes airway remodeling unless diagnosed and treated within a proper time frame. However, treatment modalities are limited because of an insufficient understanding regarding underlying pathogenic mechanisms. Several immunological and nonimmunological mechanisms have been suggested, indicating that the pathogenesis of occupational asthma may be more complex than other types of asthma. Airway epithelial cells are the first to encounter diisocyanates and orchestrate various responses, such as cytokine release, oxidative stress generation, and autoantibody formation. Some evidence supports the involvement of adaptive immune responses. Additional evidence suggests that other mechanisms are involved in diisocyanate-induced occupational asthma. One such candidate mechanism is oxidative stress. Oxidative stress has been shown to trigger and aid in the development of diisocyanate-induced occupational asthma in human samples and genetic studies, and some therapeutic trials were performed based on this finding. Diisocyanate-induced occupational asthma may be caused by a complex interaction of innate and adaptive immune responses. The knowledge presented in this review may help lead to the development of new treatment modalities through an increased understanding of occupational asthma pathogenesis.

Double Jeopardy : Acute myocardial infarction complicated by cardiogenic shock and contrast mediated anaphylactoid reaction

A 63 year-old woman who developed a severe anaphylactoidreaction to iodinated contrast in the setting of emergent percutaneous intervention(PCI) for a large anterior wall ST elevation myocardial infarction (STEMI) resulting incardiogenic shock followed by cardiopulmonary arrest necessitating placement of the patient on the arterio-venous extra corporeal membrane oxygenation (ECMO). While anaphylactoid/anaphylactic reactions to radiocontrast agents have been well documentedin literature, the development of an anaphylactoid reaction secondary to radiocontrastmedia in the setting of an ST elevation myocardial infarction (STEMI) and resultingin cardiogenic shock has never been reported. We discuss naphylactoidreactions to contrast media occurs by non-immunologic (i.e. non IgE ) mechanisms. Premedication does not abate or prevent all types of iodinated contrastmediated reactions. However, studies have shown that premedication is effective fora cutaneous reaction to iodinated contrast media (ICM). Due to the relative excellentsafety profiles of the premedication, physicians should continue to use them prior to asuspected ICM reaction.

Incidence of Non-Immunological Defenses of Soil White Grubs on Parasitism Success of Mallophora ruficauda Larva (Diptera: Asilidae).

White grubs are larvae of Coleoptera of the family Scarabaeidae. They are known because of their intensive feeding habits on crop roots. Mallophora ruficauda (Diptera: Asilidae) is a dipteran parasitoid whose larva is a natural enemy for white grubs. This species is a solitary ectoparasitoid, where both female and larva realize different steps in the host location process. Female place its eggs in high grasslands and then, the larva finds and parasitizes the host in the ground. There are nine potential hosts in the area of action of this parasitoid; however a high preference for Cyclocephala signaticollis has been observed (87% of field parasitism). It is known that many insects have developed defensive and immunological mechanisms when attacked by a parasitoid, which can be behavioral, physiological, chemical or genetic. The objectives of this work were to investigate what kind of defense and non-immunological associated mechanisms the white grubs have against this parasitoid and to understand why M. ruficauda have such a high preference for masked chafer grubs or Cyclocephala species. In particular, for each white grub species, we asked: (1) If there is a differential behavioral reaction when a parasitoid attack is simulated; (2) If body attributes of white grubs species have influence on defense behavior, and particularly for the masked chafer C. signaticollis; and (3) Why this species is the most selected by M. ruficauda. It was found that behavioral defenses of white grubs would explain the parasitism pattern of M. ruficauda larvae and its preference for C. signaticollis.

Cutaneous Adverse Reactions to Amoxicillin-Clavulanic Acid Suspension in Children: The Role of Sodium Benzoate

In Europe amoxicillin plus clavulanic acid is the most commonly prescribed antibiotic and sodium benzoate is contained in the suspension formulation as a preservative. We studied the relevance of sodium benzoate as the culprit agent. In a group of children with a history of adverse reactions to amoxicillin plus clavulanic acid suspension. A total of 89 children were enrolled over a period of 3 years (2006 - 2009). Single blind oral provocation tests (OPTs) with amoxicillin plus clavulanic acid, sodium benzoate and placebo were performed. 20 children with recurrent idiopathic urticaria were investigated as a control group. according to personal history: 70% of reactions were late in developing while 23% of reactions were immediate and for 5% of the cases it was not possible to define the timing. 8 children (8/89=9%) resulted positive to the provocation tests with amoxicillin plus clavulanic acid; ten children (10/89=11%) had positive results with sodium benzoate; 3% had a double positivity (i.e. excipient and active drug). The timing of reactions significantly differs between the Amoxicillin plus clavulanic acid and sodium benzoate groups (p=0.002). Sodium benzoate probably acts through a non-immunologic mechanism and care should be given to children allergic to sodium benzoate containing pharmaceutical formulations.

Five-year update on the mouse model of orthotopic lung transplantation: Scientific uses, tricks of the trade, and tips for success.

It has been 5 years since our team reported the first successful model of orthotopic single lung transplantation in the mouse. There has been great demand for this technique due to the obvious experimental advantages the mouse offers over other large and small animal models of lung transplantation. These include the availability of mouse-specific reagents as well as knockout and transgenic technology. Our laboratory has utilized this mouse model to study both immunological and non-immunological mechanisms of lung transplant physiology while others have focused on models of chronic rejection. It is surprising that despite our initial publication in 2007 only few other laboratories have published data using this model. This is likely due to the technical complexity of the surgical technique and perioperative complications, which can limit recipient survival. As two of the authors (XL and WL) have a combined experience of over 2500 left and right single lung transplants, this review will summarize their experience and delineate tips and tricks necessary for successful transplantation. We will also describe technical advances made since the original description of the model.

Vitamin D Receptor Genotype in Pancreas Allograft: A Pilot Study

Transplanting of pancreatic grafts is an established treatment for diabetes mellitus. Polymorphisms in genes, coding for proteins involved in an immune response, may influence immunologic and nonimmunologic mechanisms that lead to allograft loss. Vitamin D receptor agonists have been shown to increase long-term allograft survival in humans. Twenty-one pancreatic recipients transplanted in the Transplantation center of Shiraz University of Medical Sciences were selected and genotyped for the polymorphism of the vitamin D receptor genes (FokI), and the association of each genotype with acute rejection was evaluated. A control group of 100 unrelated otherwise healthy individuals, from the Iranian Blood Transfusion Organization were enrolled. The individuals were selected from Shiraz (a city located in Southern Iran), and the genotype frequency was compared with control group. The overall prevalence acute rejection was 28% (6/21). In the genotype study, homozygous FF presented in 15 patients (71%), heterozygous Ff presented in 6 patients (29%), and no homozygous ff was identified. In the control group, there were 50% with FF, 48% with Ff, and 2% with the ff genotype identified. The only genotype that was detected in rejection group was FF, while the frequency of FF in the nonrejection group was 60%. This study examined several patients to determine whether the vitamin D receptor (FokI) genotype is involved in acute allograft rejection and requires deeper investigation.

Berufliche Rhinitis und Asthma

Allergic rhinoconjunctivits and asthma are frequent diseases. About one in ten asthma cases is caused by an occupational hazard, either by an allergic or a non-immunologic mechanism. Primary or secondary preventive measures should be able to prevent these cases. Often, occupational rhinitis precedes the development of occupational asthma. Important causative agents are flours, plant and enzyme powders, laboratory animals, latex, isocyanates and hardeners, epoxy resins, acrylates, formaldehyde and welding fumes. Early diagnosis and the installation of protective measures are decisive for the prognosis of occupational respiratory disease.

Anaphylaxis during the perioperative period.

The incidence of anaphylaxis during anesthesia has been reported to range from 1 in 4000 to 1 in 25,000. Anaphylaxis during anesthesia can present as cardiovascular collapse, airway obstruction, and/or skin manifestation. It can be difficult to differentiate between immune and nonimmune mast cell-mediated reactions and pharmacologic effects from the variety of medications administered during general anesthesia. In addition, cutaneous manifestations of anaphylaxis are less likely to be apparent when anaphylaxis occurs in this setting. The evaluation of IgE-mediated reactions to medications used during anesthesia can include skin testing to a variety of anesthetic agents. Specifically, thiopental allergy has been documented by skin tests. Neuromuscular blocking agents such as succinylcholine can cause nonimmunologic histamine release, but there have also been reports of IgE-mediated reactions in some patients. Reactions to opioid analgesics are usually caused by direct mast cell mediator release rather than IgE-dependent mechanisms. Antibiotics that are administered perioperatively can cause immunologic or nonimmunologic reactions. Protamine can cause severe systemic reactions through IgE-mediated or nonimmunologic mechanisms. Blood transfusions can elicit a variety of systemic reactions, some of which might be IgE-mediated or mediated through other immunologic mechanisms. The management of anaphylactic reactions that occur during general anesthesia is similar to the management of anaphylaxis in other situations.

Immunological and Nonimmunological Effects of Indoleamine 2,3-Dioxygenase on Breast Tumor Growth and Spontaneous Metastasis Formation

The role of the tryptophan-catabolizing enzyme, indoleamine 2,3-dioxygenase (IDO1), in tumor escape and metastasis formation was analyzed using two pairs of Ido1+ and Ido1− murine breast cancer cell lines. Ido1 expression in 4T1 cells was knocked down by shRNA, and Ido1 expression in NT-5 cells was upregulated by stable transfection. Growth of Ido1− tumors and spontaneous metastasis formation were inhibited in immunocompetent mice. A higher level of cytotoxic T lymphocytes was generated by spleen cells from mice bearing Ido1− tumors than Ido1+ tumors. Tumor and metastatic growth was enhanced in immunodeficient mice, confirming an intensified immune response in the absence of Ido1 expression. However, Ido1+ tumors grow faster than Ido1− tumors in immunodeficient SCID/beige mice (lacking T, B, and NK cells) suggesting that some Ido1-controlled nonimmunological mechanisms may be involved in tumor cell growth regulation. In vitro experiments demonstrated that downregulation of Ido1 in tumor cells was associated with decreased cell proliferation, increased apoptosis, and changed expression of cell cycle regulatory genes, whereas upregulation of Ido1 in the cells had the opposite effects. Taken together, our findings indicate that Ido1 expression could exert immunological and nonimmunological effects in murine breast tumor cells.

The effect of helminth co-infection on malaria in mice: A meta-analysis

The question of how helminths may alter the course of concurrent malaria infection has attracted much interest in recent years. In particular, it has been suggested that by creating an anti-inflammatory immune environment, helminth co-infection may dampen both protective and immunopathological responses to malaria parasites, thus altering malaria infection dynamics and disease severity. Both synergistic and antagonistic interactions are reported in the literature, and the causes of variation among studies are not well understood. Here, meta-analysis of 42 mouse co-infection experiments was used to address how helminths influence malaria parasite replication and host mortality, and explore the factors explaining variation in findings. Most notably, this analysis revealed contrasting effects of helminth co-infection in lethal and resolving malaria models. Whilst co-infection exacerbated mortality and increased peak parasitaemia in ordinarily resolving malaria infections ( Plasmodium chabaudi and Plasmodium yoelii), effects among lethal malaria infections ( Plasmodium berghei) tended to be in the opposite direction with no change in parasitaemia. In the subset of experiments on cerebral malaria models ( P. berghei ANKA strain in a susceptible host), helminth co-infection significantly delayed death. These findings are consistent with the hypothesis that depending on the existing balance of pro- and anti-inflammatory responses mounted against malaria parasites in a given host, immune responses elicited by helminth co-infection may either promote or inhibit malarial disease. However, despite such broad patterns, a prominent feature of this dataset was great heterogeneity in effects across studies. A key future challenge therefore lies in explaining the biological causes of this variation, including a more thorough exploration of non-immunological mechanisms of helminth-malaria interaction.

Pathogenesis of dermatophytoses.

Dermatophytes can survive solely on outer cornified layers of the skin. The ability of certain fungi to adhere to particular host arises from numerous mechanisms and host factors, including the ability to adapt to the human body. Natural infection is acquired by the deposition of viable arthrospores or hyphae on the surface of the susceptible individual. After the inoculation in the host skin, suitable conditions favor the infection to progress through the stages of adherence and penetration. Development of host response is mostly by a T-cell mediated response of delayed-type hypersensitivity. Antibody formation does not seem to be protective. Natural defenses against dermatophytes depend on both immunological and nonimmunological mechanisms.

Cutting Edge Issues in Polymyositis

Skeletal muscle is the target tissue of immunoflogistic processes in patients affected with idiopathic inflammatory myopathies (IIM). IIM are classified into three major forms: polymyositis (PM), dermatomyositis (DM), and inclusion body myositis. Recent data suggest that, in the major subsets of myositis, antigens in muscles drive a B-cell antigen-specific immune response. Moreover, some non-immunological mechanisms have been advocated. In this regard, an increased expression of Jo-1 and Mi-2 in muscle biopsies from PM and DM patients compared to normal muscle has been demonstrated; these candidate autoantigens in myositis are expressed at high levels in regenerating muscle cells rather than in mature myotubes. Myositis autoantigen upregulation has also been observed in neoplastic tissues, thus representing a potential link between cancer and autoimmunity in myositis. Myositis-specific autoantibodies (MSA) are disease markers and target intracellular proteins involved in key processes such as translocation and nuclear transcription. Myositis target antigens encompass aminoacyl-tRNA synthetases, the Mi-2 helicase/histone deacetylase protein complex, the signal recognition particle ribonucleoprotein, together with novel target antigens including p155/140, CADM-140, and SAE. Despite their high specificity for autoimmune myositis, MSA target non-muscle restricted proteins ubiquitary to all cell types, making the specific muscle involvement difficult to explain. Non-immunological mechanisms also seem to contribute to the pathogenesis of IIM; activation of endoplasmic reticulum stress response due to muscle regeneration and inflammation but independent to MHC-1 up-regulation has been recently reported in patients with myositis.

FTY720 (fingolimod) efficacy in an animal model of multiple sclerosis requires astrocyte sphingosine 1-phosphate receptor 1 (S1P 1 ) modulation

Sphingosine 1-phosphate (S1P), a lysophospholipid, has gained relevance to multiple sclerosis through the discovery of FTY720 (fingolimod), recently approved as an oral treatment for relapsing forms of multiple sclerosis. Its mechanism of action is thought to be immunological through an active phosphorylated metabolite, FTY720-P, that resembles S1P and alters lymphocyte trafficking through receptor subtype S1P(1). However, previously reported expression and in vitro studies of S1P receptors suggested that direct CNS effects of FTY720 might theoretically occur through receptor modulation on neurons and glia. To identify CNS cells functionally contributing to FTY720 activity, genetic approaches were combined with cellular and molecular analyses. These studies relied on the functional assessment, based on clinical score, of conditional null mouse mutants lacking S1P(1) in CNS cell lineages and challenged by experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. All conditional null mutants displayed WT lymphocyte trafficking that responded normally to FTY720. In marked contrast, EAE was attenuated and FTY720 efficacy was lost in CNS mutants lacking S1P(1) on GFAP-expressing astrocytes but not on neurons. In situ hybridization studies confirmed that astrocyte loss of S1P(1) was the key alteration in functionally affected mutants. Reductions in EAE clinical scores were paralleled by reductions in demyelination, axonal loss, and astrogliosis. Receptor rescue and pharmacological experiments supported the loss of S1P(1) on astrocytes through functional antagonism by FTY720-P as a primary FTY720 mechanism. These data identify nonimmunological CNS mechanisms of FTY720 efficacy and implicate S1P signaling pathways within the CNS as targets for multiple sclerosis therapies.

Effect of cyclosporin A on proteinuria in the course of glomerulopathy associated with WT1 mutations

Denys–Drash syndrome (DDS) is characterized by progressive glomerulopathy caused by diffuse mesangial sclerosis (DMS), genitourinary defects, and a higher risk of developing Wilms’ tumor. It is commonly assumed that the DMS is unresponsive to any medications. In this report, we present a patient with Denys–Drash syndrome, in whom the cyclosporine A (CsA) was found to induce total remission. This observation and observations of other authors confirm that in genetic forms of nephrotic syndrome, the proteinuric effect of CsA may be due to a non-immunologic mechanism. We confirm the beneficial effect of CsA treatment in DDS; however, the potential nephrotoxicity of this drug will probably not allow long-term use.

Reply to F. Bellati et al

The antitumor activity of trastuzumab in human epidermal growth factor receptor 2 (HER2) –positive breast cancer has been ascribed to both immunologic and nonimmunologic mechanisms. It is unlikely that any one of these mechanisms alone is responsible for the antitumor activity of trastuzumab. We thank Bellati et al for pointing out the importance of the adaptive immune response as another mechanism involved in mediating trastuzumab antitumor activity. We agree with Bellati et al that HER2-based vaccines represent a promising therapeutic approach in the treatment of breast cancer. Our group is conducting an ongoing study combining lapatinib with a HER2-directed vaccine to further understand the role of the immune system in HER2-directed therapy antitumor activity (ClinicalTrials .gov Identifier: NCT00952692). As we have previously shown in preclinical models, total HER2 blockade using anti-HER2 antibodies generated in response to various HER2 vaccines in combination with lapatinib results in enhanced antitumor activity compared with either treatment alone. These experiments were conducted in cell culture without the addition of immune effector cells, which further implicates the role of nonimmunologic mechanisms in the antitumor activity. The clinical validation of these studies was recently demonstrated in a randomized phase III clinical trial in women with advanced stage HER2-positive breast cancer who had progressed on trastuzumab-containing therapy, where we showed the clinical benefit of combining trastuzumab with lapatinib compared with lapatinib treatment alone. This should dispel some of the concern about possible antagonistic effects of combining trastuzumab with small molecule inhibitors of ErbB2 tyrosine kinase activity. In addition, the article referenced in the correspondence of Bellati et al described the binding of lapatinib to epidermal growth factor receptor by x-ray crystallography, not HER2. To our knowledge, similar x-ray crystallographic studies of lapatinib interaction with HER2 have not been reported. Finally, we completely agree with Bellati et al and Winer and Burstein in their Editorial that greater insight into predictors of response to targeted therapies, such as trastuzumab, is needed. Quantitative HER2 status alone has clearly not been sufficient to predict for clinical response to trastuzumab. To more effectively treat individuals with HER2-positive breast cancer, a greater understanding of the tumor profile and patient immunological status that predict for clinical response to trastuzumab and potentially other HER2-targeted therapies is needed.

Definitions and mechanisms of drug hypersensitivity

Adverse drug reactions are a difficult problem faced by clinicians in everyday practice. The mechanisms of drug hypersensitivity are not well understood. This is reflected by difficulties in their classification, which is mainly based upon the current knowledge of immunologic and nonimmunologic mechanisms, onset of symptoms (immediate or nonimmediate) and morphology. For the individual patient, the correct diagnosis and classification is important because strict avoidance of the offending drug might be of vital importance. Considerable experience is required to guide management, to interpret results of investigations and to undertake drug challenges. This article summarizes the current knowledge regarding definitions and mechanisms. However, the field of drug hypersensitivity is rapidly expanding. Modern drugs such as biological agents bare hypersensitivity risks that are potentially mediated by, so far, unknown mechanisms.