Rebecca R. Saff

Membrane Fas Ligand Activates Innate Immunity and Terminates Ocular Immune Privilege

It has been proposed that the constitutive expression of Fas ligand (FasL) in the eye maintains immune privilege, in part through inducing apoptosis of infiltrating Fas+ T cells. However, the role of FasL in immune privilege remains controversial due to studies that indicate FasL is both pro- and anti-inflammatory. To elucidate the mechanism(s) by which FasL regulates immune privilege, we used an ocular tumor model and examined the individual roles of the membrane-bound and soluble form of FasL in regulating ocular inflammation. Following injection into the privileged eye, tumors expressing only soluble FasL failed to trigger inflammation and grew progressively. By contrast, tumors expressing only membrane FasL 1) initiated vigorous neutrophil-mediated inflammation, 2) terminated immune privilege, and 3) were completely rejected. Moreover, the rejection coincided with activation of both innate and adaptive immunity. Interestingly, a higher threshold level of membrane FasL on tumors is required to initiate inflammation within the immune privileged eye, as compared with nonprivileged sites. The higher threshold is due to the suppressive microenvironment found within aqueous humor that blocks membrane FasL activation of neutrophils. However, aqueous humor is unable to completely block the proinflammatory effects of tumor cells that express high levels of membrane FasL. In conclusion, our data indicate that the function of FasL on intraocular tumors is determined by the microenvironment in conjunction with the form and level of FasL expressed.

Opposing Roles for Membrane Bound and Soluble Fas Ligand in Glaucoma-Associated Retinal Ganglion Cell Death

Glaucoma, the most frequent optic neuropathy, is a leading cause of blindness worldwide. Death of retinal ganglion cells (RGCs) occurs in all forms of glaucoma and accounts for the loss of vision, however the molecular mechanisms that cause RGC loss remain unclear. The pro-apoptotic molecule, Fas ligand, is a transmembrane protein that can be cleaved from the cell surface by metalloproteinases to release a soluble protein with antagonistic activity. Previous studies documented that constitutive ocular expression of FasL maintained immune privilege and prevented neoangeogenesis. We now show that FasL also plays a major role in retinal neurotoxicity. Importantly, in both TNFα triggered RGC death and a spontaneous model of glaucoma, gene-targeted mice that express only full-length FasL exhibit accelerated RGC death. By contrast, FasL-deficiency, or administration of soluble FasL, protected RGCs from cell death. These data identify membrane-bound FasL as a critical effector molecule and potential therapeutic target in glaucoma.

Safety and Outcomes of Test Doses for the Evaluation of Adverse Drug Reactions: A 5-Year Retrospective Review

BACKGROUND Graded challenges are the criterion standard for evaluating adverse drug reactions (ADR). Evidence-based guidelines regarding the optimal number of steps for challenges are lacking. OBJECTIVE To determine the safety and outcomes of 1- or 2-step test doses among patients with ADRs seen by the allergy/immunology consult service and to compare the outcomes of 1- or 2-step test doses with multistep challenges performed during the same time period. METHODS We conducted a retrospective chart review of all 1- or 2-step test doses and multistep challenges at a single academic center between 2008 and 2013. Patient demographics, symptoms of initial ADRs, and outcomes of test doses and multistep challenges were reviewed. ADRs were classified by type and were graded by severity. Outcomes of 1- or 2-step test doses were compared with multistep challenges. RESULTS We identified 456 patients who underwent 497 one- or 2-step test doses (mean age, 51 years; 67.5% female patients). The most common drugs that prompted test doses were β-lactams (62%). The majority of patients (n = 444 [89%]) did not experience any ADRs during test doses. ADRs that occurred during test doses (n = 53 [11%]) were most commonly non-immune-mediated (45%) or IgE-mediated (32%), with grade 1 or 2 severity (100%). Forty-nine percent of ADRs during test doses did not receive any treatment. The ADR rate during multistep challenges (10/82 [12%]) was similar to test doses. CONCLUSION One- or 2-step test doses were safe for evaluation of ADRs. Multistep challenges did not confer added safety. Furthermore, 1- or 2-step test doses did not raise concern for induction of tolerance.

Activation-Induced Cell Death Limits Effector Function of CD4 Tumor-Specific T Cells

A number of studies have documented a critical role for tumor-specific CD4+ cells in the augmentation of immunotherapeutic effector mechanisms. However, in the context of an extensive tumor burden, chronic stimulation of such CD4+ T cells often leads to the up-regulation of both Fas and Fas ligand, and coexpression of these molecules can potentially result in activation-induced cell death and the subsequent loss of effector activity. To evaluate the importance of T cell persistence in an experimental model of immunotherapy, we used DO11 Th1 cells from wild-type, Fas-deficient, and Fas ligand-deficient mice as effector populations specific for a model tumor Ag consisting of an OVA-derived transmembrane fusion protein. We found that the prolonged survival of Fas-deficient DO11 Th1 cells led to a more sustained tumor-specific response both in vitro and in vivo. Importantly, both Fas- and Fas ligand-deficient Th1 cells delayed tumor growth and cause regression of established tumors more effectively than wild-type Th1 cells, indicating that resistance to activation-induced cell death significantly enhances T cell effector activity.

Control of Ocular Tumor Growth and Metastatic Spread by Soluble and Membrane Fas Ligand

Fas ligand (FasL) can be either membrane bound, or cleaved by metalloproteinases (MMP) to produce a soluble protein. The two different forms of FasL are reported to have opposite functions-membrane-bound FasL (mFasL) is proinflammatory and soluble FasL (sFasL) is antiinflammatory. We previously showed that, within the immune-privileged eye, tumors expressing high levels of mFasL overcame the suppressive ocular environment, triggered an inflammatory response, and were subsequently rejected. By contrast, eye tumors expressing low levels of mFasL grew progressively. To evaluate the effect of sFasL on the tumor growth and metastatic potential of ocular FasL-expressing tumors, we compared tumor cell clones that expressed equal amounts of (low) mFasL in the presence or absence of sFasL. Tumor cells transfected with a modified FasL gene expressed only mFasL (noncleavable), grew progressively within the eye, and induced systemic protective immunity that prevented metastatic spread of tumor cells to the liver. Unexpectedly, tumors transfected with wild-type FasL (wtFasL; cleavable), which could produce both sFasL and mFasL, elicited considerably more inflammation and grew more slowly within the eye. However, the cleavable wtFasL eye tumors failed to trigger protective immunity and gave rise to liver metastases. Interestingly, exposure to the ocular environment was required for the wtFasL tumors to gain metastatic potential. We conclude that the fate of FasL-expressing tumors is determined by a combination of the following: (a) the relative proportion of membrane and sFasL, and (b) the local environment that determines the extent of FasL cleavage.

Evaluation and management of a patient with multiple drug allergies.

Multiple drug allergy syndrome (MDAS) is a clinical diagnosis made in patients with adverse reactions to two or more structurally unrelated drugs with an underlying immune-mediated mechanism causing the reaction. The evaluation of a patient with MDAS begins with a comprehensive drug allergy history and consideration of the underlying immune mechanism for each reaction. Skin testing is a useful diagnostic tool; however, the only validated immediate hypersensitivity skin testing is for penicillin where the antigenic determinants have been identified. Skin testing to most other drugs, although not validated, can be considered using a nonirritating concentration (NIC). In general, skin test positivity using an NIC suggests that the drug should be avoided, but a negative result does not rule out an IgE-mediated allergy. A test dose, also called a drug provocation test, graded oral challenge, or incremental challenge, should be performed when there is a low likelihood of an IgE-mediated mechanism for the reaction. In patients with a recent IgE-mediated hypersensitivity reaction or positive skin testing with no reasonable alternative treatment options, desensitization protocols can be used to allow the patient to safely receive a necessary drug. The evaluation of patients with MDAS is both challenging and time-consuming for the practicing allergist, who must systematically evaluate each reaction to help determine which drugs can be safely used again in the future. The molecular mechanisms and risk factors for this condition remain poorly understood, but research to further understand this condition is ongoing.

Management of patients with nonaspirin-exacerbated respiratory disease aspirin hypersensitivity reactions.

Because of widespread use, nonsteroidal anti-inflammatory drugs (NSAIDs) are the second most common cause of all adverse drug reactions, with hypersensitivity reported in ∼1% of the population. NSAID hypersensitivity can be categorized into five types by the underlying disease, symptoms of reaction, and timing of reaction. These include rhinitis and asthma induced by NSAIDs (also known as aspirin-exacerbated respiratory disease), NSAID-exacerbated cutaneous disease (NECD), urticaria or angioedema induced by multiple NSAIDs, single NSAID-induced reactions, and delayed NSAID reactions. NECD occurs in one-third of patients with chronic urticaria who develop an exacerbation of their urticaria, sometimes with angioedema, typically beginning 30-90 minutes after ingestion of NSAIDs that inhibit cyclooxygenase (COX)-1. In urticaria or angioedema induced by multiple NSAIDs, patients without underlying disease develop urticaria or angioedema 30-90 minutes after ingestion of COX-1-inhibiting NSAIDs including aspirin. Single NSAID-induced reactions are immediate and specific to a single NSAID and are thought to occur because of an IgE-mediated reaction against a specific epitope of the NSAID. Delayed NSAID reactions occur days to weeks after initiating an NSAID. These are T-cell mediated and not amenable to desensitization or rechallenge. Classifying the type of NSAID hypersensitivity is important because many patients with a prior history of urticaria or angioedema induced by multiple NSAIDs will often tolerate aspirin test dose. This would allow the use of an aspirin for primary or secondary prevention in patients with coronary artery disease despite a presumed history of NSAID hypersensitivity.

Identification of Inpatient Allergic Drug Reactions Using ICD-9-CM Codes

BACKGROUND The study of allergic drug reactions has been limited because of challenges in identifying and confirming cases. OBJECTIVE To determine the utility of International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes for identifying inpatient allergic drug reactions and to compare findings with previous data in the emergency department. METHODS By reviewing medical records of inpatients with ICD-9-CM codes and E codes suggestive of allergic drug reactions at a large urban academic medical center, we determined codes that yielded the most drug allergy cases and identified culprit drugs. RESULTS In 2005 and 2010, 3337 and 5282 possible allergic drug reactions during hospitalization were identified and 1367 were reviewed. Allergic drug reactions were found in 409 (30.1%) of the reviewed charts, with 172 (29.7%) in 2005 and 237 (30.5%) in 2010. The codes that identified the highest percentage of true allergic drug reactions were dermatitis due to drug (693.0), allergic urticaria (708), angioneurotic edema (995.1), and anaphylaxis (995.0). Antibiotics were the most common cause (44.4%); however, multiple drug classes were often identified as likely culprit drugs. CONCLUSION Specific ICD-9-CM codes can identify patients with allergic drug reactions, with antibiotics accounting for almost half of true reactions. Most patients with codes 693.0, 995.1, 708, and 995.0 had allergic drug reactions, with 693.0 as the highest yield code. An aggregate of multiple specific codes consistently identifies a cohort of patients with confirmed allergic drug reactions.