Leyva-Castillo JM, Strakosha M, Smith SEM, Vega-Mendoza D, Elkins M, et al.
bioRxiv : the preprint server for biology β’
Tick bites often promote local allergic reactions in the skin and predispose to red meat allergy. The mechanisms involved in these processes are not fully understood. Here we investigated the local changes to the skin and intestine induced by tick bites. C3H/HEN or Balb/c mice were subjected to either tick bites by ( ) or mechanical skin injury. Skin or intestine was analyzed a different time point by transcriptomic and histological techniques. Our results indicate that bites promote epidermal hyperplasia, spongiosis and an accumulation of eosinophils and mast cells in the bitten skin. In addition, bites promote the expression of genes and activate pathways also induced by mechanical skin injury elicited by tape stripping. Remarkably, similar to tape stripping, bites promote an increase in total serum IgE, and intestinal tuft cell and mast cell expansion. bites in mice promote cutaneous inflammation that resembles allergic skin inflammation, as well as intestinal changes that could play a role in the predisposition to red meat allergy.
Ticks are hematophagous arthropods that transmit disease-causing pathogens worldwide. Tick saliva deposited into the tick-bite site is composed of an array of immunomodulatory proteins that ensure successful feeding and pathogen transmission. These salivary proteins are often glycosylated, and glycosylation is potentially critical for the function of these proteins. Some salivary glycans are linked to the phenomenon of red meat allergy - an allergic response to red meat consumption in humans exposed to certain tick species. Tick salivary glycans are also invoked in the phenomenon of acquired tick resistance wherein non-natural host species exposed to tick bites develop an immune response that thwarts subsequent tick feeding. This review dwells on our current knowledge of these two phenomena, thematically linked by salivary glycans.
Alpha-gal syndrome (AGS) is a hypersensitivity reaction to mammalian meat that develops after tick bite exposure. AGS was first described in 2009 and testing for the allergy has become available in the last decade. We report the case of a 56-year-old farmer with a history of frequent lone star tick bites who presented with a 7-year history of diffuse urticaria occurring hours after eating red meat. AGS is likely underdiagnosed because of the unusual presentation of the allergy, historic lack of available testing, and deficiency of physician knowledge about the condition. Recognition of AGS is important both to help alleviate symptom burden and to avoid iatrogenesis. Patients with AGS should not receive products containing mammalian products, such as cat-gut suture, porcine-derived heart valves, and bovine-derived vaccines. Patients with AGS may present in a variety of clinical environments and physicians of all kinds should be able to recognise the symptoms.
Humoral immunity to pathogens and other environmental challenges is paramount to maintain normal health, and individuals lacking or unable to make antibodies are at risk. Recent studies indicate that many human protective antibodies are against carbohydrate antigens; however, little is known about repertoires and individual variation of anti-carbohydrate antibodies in healthy individuals. Here we analyzed anti-carbohydrate antibody repertoires (ACARs) of 105 healthy individual adult donors, aged 20-60 from different ethnic backgrounds to explore variations in antibodies, as defined by binding to glycan microarrays and by affinity purification. Using microarrays that containedβ>β1,000 glycans, including antigens from animal cells and microbes, we profiled the IgG and IgM ACARs from all donors. Each donor expressed many ACAs, but had a relatively unique ACAR, which included unanticipated antibodies to carbohydrate antigens not well studied, such as chitin oligosaccharides, Forssman-related antigens, globo-type antigens, and bacterial glycans. We also saw some expected antibodies to ABO(H) blood group and Ξ±-Gal-type antigens, although these also varied among individuals. Analysis suggests differences in ACARs are associated with ethnicity and age. Thus, each individual ACAR is relatively unique, suggesting that individualized information could be useful in precision medicine for predicting and monitoring immune health and resistance to disease.
Annals of allergy, asthma & immunology : official publication of the American College of Allergy, Asthma, & Immunology β’
Hypersensitivity reactions to antineoplastic agents may lead to discontinuation of first-line treatments. Rapid drug desensitization (RDD) allows for a safe reintroduction in patients who are allergic to them. To evaluate the safety and efficacy of the Brigham and Women's Hospital's 12-step RDD in a Portuguese patient population with cancer and to identify markers associated with breakthrough reactions (BTRs) to platins. We conducted a retrospective review of desensitizations undertaken at the Immunoallergology Day-Care Unit of the Santa Maria Hospital in Lisbon, Portugal, from July 2008 to July 2019. Adult patients with cancer and with immediate hypersensitivity reactions were included. Skin testing was performed to platins, trastuzumab, and cetuximab. The 12-step protocol was used for most patients, and a shorter protocol was used in 9 patients who were taxane-reactive to resume regular infusions. A total of 1471 RDDs were performed in 272 patients to 136 platins, 124 taxanes, 13 monoclonal antibodies, and 10 other drugs. Skin test results were positive in 127 of patients who were platin-reactive (95.3%) and negative in patients who were cetuximab- and trastuzumab-reactive. There were 141 BTRs during RDD (9.6% of infusions), 79.4% induced by platins with the majority having mild reactions (68.8%). There were 8 patients who were paclitaxel-reactive, and who completed a shorter protocol and resumed regular infusions successfully. Multiple platin infusions (cutoff: β₯10) and total immunoglobulin E greater than or equal to 100 U/mL were identified as independent risk factors for BTRs in patients who were platin-reactive. This large single-center study confirmed the safety and efficacy of the 12-step RDD protocol in a diverse cancer population, providing evidence of its universal applications. Total immunoglobulin E is a potentially useful biomarker to identify high-risk patients who are platin-reactive.
Iweala OI, Choudhary SK, Addison CT, Batty CJ, Kapita CM, et al.
The Journal of allergy and clinical immunology β’
Alpha-gal-containing glycolipids activate basophils sensitized with plasma from alpha-gal allergic subjects in an IgE-dependent manner suggesting a role for glycolipid in the effector phase of IgE-mediated food allergy.
The journal of allergy and clinical immunology. In practice β’
Biological agents are used in the treatment of neoplastic, autoimmune, and inflammatory diseases and their clinical applications are becoming broader. Following their increased utilization, hypersensitivity reactions linked to these drugs have become more frequent, sometimes preventing the use of first-line therapies. The clinical presentation of hypersensitivity reactions to biological agents ranges from mild cutaneous manifestations to life-threatening reactions. In this scenario, rapid desensitization is a groundbreaking procedure that enables selected patients to receive the full treatment dose in a safe way, in spite of their immediate hypersensitivity reaction to the drug, and protects them against anaphylaxis. The aim of this review is to update and discuss some of the main biological agents used in clinical practice (rituximab, trastuzumab, cetuximab, ofatumumab, tocilizumab, brentuximab, omalizumab, and tumor necrosis factor alpha inhibitor agents) and their associated hypersensitivity reactions, including clinical presentations, diagnosis, and treatment in the acute setting. In addition, novel management options with rapid desensitization are presented.
Decellularized biologic matrices are plausible biomedical materials for the bioengineering in liver transplantation. However, one of the concerns for safe medical application is the lack of objective assessment of the immunogen within the materials and the in vivo immune responses to the matrices. The purpose of this study was the production of immunogen-reduced and biocompatible matrices from porcine liver. In the present study, 0.1% SDS solution was effective for removing DNA fragments and sequences encoding possible immunogenic and viral antigens within the matrices. The PCR analysis showed that galactose-Ξ±-1,3 galactose Ξ²-1,4-N-acetylglucosamine (1,3 gal), swine leukocyte antigen (SLA), and porcine endogenous retrovirus (PERV) were completely removed in the matrices. Collagen and glycosaminoglycans (GAGs) were preserved over 63%-71%, respectively, compared to those of native liver. The implanted decellularized tissues showed minimal host responses and naturally degraded within 10 weeks. In this study, we produced immunogen-reduced and biocompatible extracellular matrices from porcine liver. Although future investigations would be required to determine the mechanism of the host reaction, this study could provide useful information of porcine liver-derived biologic matrices for liver researches.
Rupture of ACL is a common injury. While the current surgical treatments are effective, many patients still suffer from precocious osteoarthritis, and there is an increasing interest in bioengineering approaches to improve ACL repair. Bovine collagen is a material currently in use for tissue engineering of ligaments. The alpha-gal epitopes found on bovine cells are a source of immunogenic stimulus for human cells. In this study, we wished to determine if those epitopes could be removed sufficiently to mitigate an immunogenic response using either a decellularization protocol or decellularization followed by alpha-galactosidase treatment. Bovine ACLs were treated with Triton-X, sodium deoxycholate, ribonuclease, and deoxyribonuclease to remove cells. A subset of the decellularized tissues was further treated with alpha-galactosidase. Human peripheral blood mononuclear cells (PBMCs) were exposed to untreated, decellularized, and alpha-galactosidase-treated tissues, and PBMC migration and IL-6 release were measured. PBMCs were significantly more attracted to untreated ACL compared to decellularized or alpha-galactosidase-treated tissue, but no difference was seen between the two treatment groups. PBMCs also released significantly more IL-6 when exposed to untreated tissue compared to decellularized ACL or alpha-galactosidase-treated ACL, but no difference was seen between the two treatment groups. Immunohistochemistry using anti-alpha-gal antibody detected the epitopes throughout the untreated ACL, but similar areas of reaction were not seen on decellularized or alpha-galactosidase-treated ACL. These results suggest that our decellularization protocol minimizes the immunogenic reactions of human PBMCs to bovine ACL tissue. Therefore, decellularized bovine ACL tissue may be a safe, effective biomaterial for ACL injury treatments.
Hong DI, Bankova L, Cahill KN, Kyin T, Castells MC
Expert review of clinical immunology β’
Monoclonal antibodies are important therapeutic tools, but their usefulness is limited in patients who experience acute infusion reactions, most of which are consistent with type I hypersensitivity reactions including anaphylaxis. Patients who experience acute infusion reactions face the prospect of stopping treatment or switching to an alternative, and potentially more toxic or inferior treatment. Another option that overcomes the treatment hurdle of these reactions is rapid desensitization, a procedure in which the offending agent is re-administered in a step-wise, highly controlled fashion. While the risk of reactions is not completely eliminated, desensitization has proven to be a highly effective re-administration strategy for most patients who otherwise would not be able to tolerate their monoclonal antibody therapy owing to drug-induced anaphylaxis. This article reviews the current literature on desensitization and other readministration protocols to monoclonal antibodies with an emphasis on four agents: rituximab, infliximab, cetuximab and trastuzumab.
Wadlow RC, Hezel AF, Abrams TA, Blaszkowsky LS, Fuchs CS, et al.
The oncologist β’
Cetuximab and panitumumab are monoclonal antibodies that target the epidermal growth factor receptor (EGFR) and are approved for the treatment of patients with KRAS wild-type meta-static colorectal cancer. There are no data that describe the activity of panitumumab in patients with progressive disease on cetuximab. We performed a single-arm phase II trial of panitumumab in patients with KRAS wild-type metastatic colorectal cancer that had progressed on prior cetuximab. We used a two-stage study design to treat patients with panitumumab at 6 mg/kg every 14 days (cycle length = 28 days). Treatment was continued until disease progression, death, inability to tolerate panitumumab, or study withdrawal. The primary endpoint was response rate; secondary endpoints included progression-free survival and overall survival. Twenty patients were treated in the first stage, with plans to treat an additional twelve patients if there was at least one objective response. We collected blood samples at baseline and prior to cycles 2 and 3 to evaluate for the presence of anti-cetuximab and anti-panitumumab antibodies. We treated twenty patients for a median of two cycles (range 1-4). No patients responded, and 45% had a best response of stable disease (no progression for at least two cycles). Median progression-free survival was 1.7 months and median overall survival was 5.2 months. Panitumumab was well tolerated. Thirteen patients (65%) had grade 1-2 dry skin or rash, and three patients had treatment-related grade 3 toxicities (one each with hyperglycemia, hyperbilirubinemia, and hypokalemia). No patients had detectable anti-cetuximab antibodies at any time point; one patient developed anti-panitumumab antibodies. Panitumumab has minimal benefit in patients with KRAS wild-type metastatic colorectal cancer that has progressed on prior cetuximab. Discussion Both cetuximab and panitumumab competitively inhibit ligand binding to EGFR, thereby promoting receptor internalization and blocking receptor-mediated signaling. Although the two agents have never been compared directly in a randomized clinical trial, they produce similar response rates when used alone as well as in combination with cytotoxic agents. Cetuximab is a chimeric antibody with approximately 30% murine protein, while panitumumab is a fully human monoclonal antibody. Correspondingly, rates of severe hypersensitivity reactions are somewhat increased with cetuximab (3%) compared to panitumumab (1%). However, the potential efficacy of panitumumab in patients who have developed disease progression on cetuximab has been an open question. Metges et al. (PANERB trial) prospectively treated 32 KRAS wild-type metastatic colorectal cancer patients with cetuximab and irinotecan followed by panitumumab monotherapy after progression. Remarkably, the authors reported an objective response rate of 22% to panitumumab, including a disease control rate (objective response plus stable disease) of 73% in 11 patients who had previously responded to cetuximab and irinotecan. In contrast, we found no responders and a stable disease rate of 45% with a median duration of only 1.7 months in our trial of 20 patients. Moreover, no patients had detectable anti-cetuximab antibodies at baseline. It is not clear to what extent the PANERB trial included patients without objective disease progression on cetuximab or for whom cetuximab-containing regimens may have been ceased due to toxicity in the absence of disease progression. In both circumstances, retreatment with panitumumab may be expected to demonstrate some degree of clinical activity. In our study, disease progression after at least 4 weeks of cetuximab documented radiographically or by increased carcinoembryonic antigen (CEA) levels was required for inclusion in order to ensure that the study population demonstrated unequivocal evidence of progression on cetuximab. While it remains possible that a small subset of patients may benefit from panitumumab after progression on cetuximab, our results suggest that this approach should not be adopted until predictive biomarkers for panitumumab response in this setting have been discovered and validated. Until then, patients who develop progression on cetuximab should be enrolled in trials of novel agents.
Chung CH, Mirakhur B, Chan E, Le QT, Berlin J, et al.
The New England journal of medicine β’
Cetuximab, a chimeric mouse-human IgG1 monoclonal antibody against the epidermal growth factor receptor, is approved for use in colorectal cancer and squamous-cell carcinoma of the head and neck. A high prevalence of hypersensitivity reactions to cetuximab has been reported in some areas of the United States. We analyzed serum samples from four groups of subjects for IgE antibodies against cetuximab: pretreatment samples from 76 case subjects who had been treated with cetuximab at multiple centers, predominantly in Tennessee, Arkansas, and North Carolina; samples from 72 control subjects in Tennessee; samples from 49 control subjects with cancer in northern California; and samples from 341 female control subjects in Boston. Among 76 cetuximab-treated subjects, 25 had a hypersensitivity reaction to the drug. IgE antibodies against cetuximab were found in pretreatment samples from 17 of these subjects; only 1 of 51 subjects who did not have a hypersensitivity reaction had such antibodies (P<0.001). IgE antibodies against cetuximab were found in 15 of 72 samples (20.8%) from control subjects in Tennessee, in 3 of 49 samples (6.1%) from northern California, and in 2 of 341 samples (0.6%) from Boston. The IgE antibodies were shown to be specific for an oligosaccharide, galactose-alpha-1,3-galactose, which is present on the Fab portion of the cetuximab heavy chain. In most subjects who had a hypersensitivity reaction to cetuximab, IgE antibodies against cetuximab were present in serum before therapy. The antibodies were specific for galactose-alpha-1,3-galactose.
Kuwaki K, Knosalla C, Moran K, Alt A, Katopodis AG, et al.
Xenotransplantation β’
To investigate the specificity of anti-Galalpha1,3Gal (Gal) antibodies (Abs) with respect to Gal oligosaccharides of types 2 and 6, eight baboons received an intravenous infusion of either a poly-l-lysine conjugate of Gal type 2 (n = 5) or type 6 (n = 3), followed 48 h later by the alternative Gal type 6 or 2 conjugate, respectively. IgM Abs reactive to Gal type 2 were depleted by 80 to 89% by either Gal conjugate. IgM reactive to Gal type 6 was less efficiently depleted by the Gal type 2 conjugate (57% depletion) than the Gal type 6 (82% depletion). Gal-reactive IgG was depleted more slowly and less efficiently by either glycoconjugate (initially by only 28 to 54%). Our results indicate that the Gal type 6 conjugate depletes most anti-Gal IgM, but the Gal type 2 conjugate is less efficient in depleting anti-Gal IgM reactive with type 6. There remain small fractions of antibody that are unadsorbed, particularly of IgG, probably due to their low affinity and distribution in both the intra- and extra-vascular compartments.
Peritoneal cavity B-1 cells are believed to produce IgM natural Abs. We have used alpha1,3-galactosyltransferase-deficient (GalT(-/-)) mice, which, like humans, produce IgM natural Abs against the carbohydrate epitope Galalpha1,3Gal (Gal), to demonstrate that peritoneal cavity B-1b cells with anti-Gal receptors produce anti-Gal IgM Abs only after LPS stimulation. Likewise, peritoneal cavity cells of GalT(-/-) and wild-type mice do not produce IgM Abs of other specificities without LPS stimulation. Development of Ab-secreting capacity is associated with loss of CD11b/CD18 (Mac-1) expression. In contrast, there are large numbers of cells producing anti-Gal and other IgM Abs in fresh splenocyte preparations from GalT(-/-) and (for non-Gal specificities) wild-type mice. These cells are Mac-1(-) but otherwise B-1b-like in their phenotype. We therefore hypothesized a pathway wherein peritoneal cavity B cells migrate into the spleen after activation in vivo and lose Mac-1 expression to become IgM Ab-producing cells. Consistent with this possibility, splenectomy reduced anti-Gal Ab production after immunization of GalT(-/-) mice with Gal-positive rabbit RBC. Furthermore, splenectomized B6 GalT(-/-), Ig micro -chain mutant ( micro (-/-)) (both Gal- and B cell-deficient) mice produced less anti-Gal IgM than nonsplenectomized controls after adoptive transfer of peritoneal cavity cells from B6 GalT(-/-) mice. When sorted GalT(-/-) Mac-1(+) peritoneal cavity B cells were adoptively transferred to B6 GalT(-/-), micro (-/-) mice, IgM Abs including anti-Gal appeared, and IgM-producing and Mac1(-) B cells were present in the spleen 5 wk after transfer. These findings demonstrate that peritoneal cavity Mac-1(+) B-1 cells are precursors of Mac-1(-) splenic IgM Ab-secreting cells.
BΓΌhler L, Deng S, O'Neil J, Kitamura H, Koulmanda M, et al.
Xenotransplantation β’
The aim of the present study was to assess the survival of adult porcine islets transplanted into baboons receiving either (I) conventional triple drug immunosuppressive therapy or (2) a non-myeloablative regimen and an anti-CD154 monoclonal antibody (mAb) aimed at tolerance-induction. Group 1 baboons (n = 3) were pancreatectomized prior to intraportal injection of 10,000 porcine islet equivalents (IE)/kg and immunosuppressed with anti-thymocyte globulin (ATG), cyclosporine and azathioprine. In Group 2 (n = 2), non-pancreatectomized baboons underwent induction therapy with whole body and thymic irradiation, and ATG. Extracorporeal immunoadsorption (EIA) of anti-Galalpha1,3Gal (Gal) antibody was carried out. Maintenance therapy was with cobra venom factor, cyclosporine. mycophenolate mofetil, methylprednisolone and anti-CD154 mAb. Porcine islets were injected intraportally (14,000 and 32,000 IE/kg, respectively) and high-dose pig mobilized peripheral blood progenitor cells (3 x 10(10) cells/kg) were infused into a systemic vein. Porcine islets were also implanted in the sternomastoid muscle to facilitate subsequent biopsies. In both groups. porcine C-peptide was measured, and histological examination of liver or sternomastoid muscle biopsies was performed at regular intervals. In Group 1, total pancreatectomy reduccd human C-peptide to < 0.1 ng/ml and induced insulin-requiring diabetes. The transplantation of porcine islets was followed by normalization of glycemia for 15-24 h. Porcine C-peptide was detected only transiently immediately after porcine islet injection (maximum 0.12 ng/ml). Histological examination of liver biopsies taken between days 2 and 19 did not reveal viable islets, but necrotic cell structures with mononuclear cell infiltrates were identified in portal venules. In Group 2, injection of porcine islets into non-pancreatectomized recipients induced a transient hypoglycemia (2-4 h) requiring concentrated intravenous dextrose administration. Porcine C-peptide was detectable for 5 and 3 days (maximum 2.8 and 1.0 ng/ml), respectively. Baboon #4 died on day 12 from small bowel intussusception. Liver and sternomastoid muscle biopsies showed well-preserved porcine islets, staining positive for insulin and glucacon, without signs of rejection. In baboon #5, viable islets were detected in the sternomastoid muscle biopsy on day 14, but not on day 28 or thereafter. A progressive mononuclear cell and macrophage infiltration was seen in the biopsies. In conclusion, conventional immunosuppression allowed survival of porcine islets in baboons for < 24 h. The non-myeloablative regimen prolonged survival of porcine islets for > 14 days. However, despite depletion of T cells, anti-Gal antibody and complement, and CD154-hlockade, porcine islets were rejected by day 28. These results suggest that powerful innate immune responses are involved in rejection of discordant xenogencic islets.
Molecular therapy : the journal of the American Society of Gene Therapy β’
Expression of retrovirally transduced genes in bone marrow-derived cells can be used to establish stable long-term B- and T-cell tolerance. To determine whether preexisting antibodies may prohibit the use of gene therapy to establish tolerance, we examined the extent to which preexisting antibodies specific for the carbohydrate antigen Gal alpha1-3Gal beta1-4GlcNAc-R (alpha Gal) could affect engraftment and development of bone marrow progenitors expressing the enzyme UDPgalactose:beta-D-galactosyl-1,4-N-acetyl-D-glucosaminide alpha(1-3)galactosyltransferase (E.C. 2.4.1.151), or simply alpha GT, which synthesizes the alpha Gal epitope. Groups of alpha GT knockout mice (GT(0) mice) lacking alpha Gal were presensitized to alpha Gal by immunization and then lethally irradiated and reconstituted with varying numbers of alpha GT-transduced syngeneic bone marrow cells. Whereas unimmunized controls were reconstituted with as few as 2 x 10(6) transduced cells, a significant fraction of immunized mice reconstituted with 2 x 10(6) or 4 x 10(6) alpha GT-transduced cells failed to undergo bone marrow engraftment and died. Immunized mice in which radiation protection was achieved failed to express alpha Gal. However, radiation protection and expression of alpha Gal on bone marrow-derived cells, resulting in tolerance, could be achieved by increasing the number of transduced cells used to reconstitute immunized mice. Thus, although high levels of preexisting antibodies can be a significant barrier to engraftment, this barrier can be overcome by increasing the number of transduced cells used for reconstitution.
It has been reported that T-cell depletion by in vivo treatment with monoclonal antibodies results in polyclonal B-cell activation. However, its effects on B cells responding to Galalpha1,3Gal (Gal) epitopes remain unknown. alpha1,3-Galactosyltransferase-deficient (GalT-/-) mice were treated with depleting anti-CD4 and CD8 monoclonal antibodies. The kinetics of anti-Gal natural antibodies (NAb) and total immunoglobulin levels in their sera were evaluated. The frequencies of anti-Gal NAb-producing cells were determined in the various tissues of GalT-/- mice by enzyme-linked immunospot assay. In vivo T-cell depletion led to significant increases in both anti-Gal IgM and total IgM levels in sera of GalT-/- mice, but did not influence either anti-Gal IgG or total IgG levels. An increased frequency of anti-Gal and total IgM-producing cells was observed in the spleens and bone marrow of T-cell-depleted GalT-/-mice but not in peritoneal cavity cells. In vivo T-cell depletion facilitates anti-Gal IgM production, suggesting that T cells deliver inhibitory signals to B cells responding to Gal.
Watts A, Foley A, Awwad M, Treter S, Oravec G, et al.
Xenotransplantation β’
Anti-Galalpha1-3Gal (Gal) antibodies (Gal Ab) contribute to the rejection of porcine organs transplanted into primates. Extracorporeal immunoadsorption (EIA) has been developed to eliminate Gal Ab from the circulation. Between 1995 and 1999 we performed 320 EIAs in baboons using a COBE-Spectra apheresis unit incorporating a synthetic Gal immunoaffinity column. Three plasma volumes were immunoadsorbed on each occasion. The 221 consecutive EIAs performed in 41 immunosuppressed baboons between January 1997 and April 1999 form the basis of this review. Of these 41 baboons, 29 underwent a series of three or four EIAs at daily intervals, seven had multiple series of three EIAs, and the remainder underwent single or double EIAs. Serum Gal Ab levels were monitored by ELISA before and at intervals after the course of EIA. There were two fatal complications, one from a respiratory mishap (unrelated to the EIA) and one from persistent hypotension unresponsive to therapeutic interventions. Seven procedures (3%) were terminated early owing to technical difficulties and/or persistent hypotension. Mean pre-EIA Gal Ab levels in naive baboons were 33.1 microg/ml (IgM) and 14.5 microg/ml (IgG). Immediately after three consecutive EIAs, IgM was depleted by a mean of 97.3% and IgG by 99.4%. By 18 to 24 h later, Gal Ab was returning but depletion remained at 80.1% (IgM) and 84.7% (IgG). The subsequent rate of return of Gal Ab depended on the immunomodulatory protocol used. (1) With appropriate monitoring, EIA is an acceptably safe procedure, even in small (<10 kg) baboons. (2) Three consecutive EIAs are effective in removing >97% of Gal Ab. (3) In the majority of cases, return of Gal Ab begins within 24 h, irrespective of the immunomodulatory protocol.
