Search of a genomic sequence database for potential novel blood group antigens: Investigation into why some amino acid substitutions are not immunogenic.

BACKGROUND: Polypeptide blood group antigens are typically identified through investigation of the antibodies they induce. Human genome sequence databases are a new tool to identify AA substitutions that potentially create blood group antigens. STUDY DESIGN AND METHODS: The Erythrogene genomic sequence database was searched for missense mutations not known to be blood group antigens in the extracellular domains of selected RBC proteins in European populations. Any mutations found with prevalence of 1%-90% and not known to have induced antibodies in transfusion practice were analyzed using protein structural analysis and epitope prediction programs to determine why they apparently lack immunogenicity. RESULTS: Thirteen missense mutations not known to create blood group antigens were identified in the extracellular domains of Kell, BCAM, and RhD proteins, but not in RhCE, Urea Transporter 1 (Kidd), Atypical Chemokine Receptor 1 (Duffy), glycophorin A or glycophorin B. While 11 of the 13 mutations had low prevalence (<1%), a Kell Ser726Pro substitution and a BCAM Val196Ile substitution had predicted phenotype prevalences of 43.2% and 5.7%, respectively. Ser726Pro had multiple properties of a linear B-cell epitope, but possible suboptimal protein location for B-cell receptor binding and limited T-cell epitope possibilities. Val196Ile was not predicted to be in a linear B-cell epitope. CONCLUSION: Multiple potential new blood group antigens of low prevalence were identified. Whether they are antigenic remains to be determined. Two higher prevalence variants in Kell and BCAM are unlikely antigens, otherwise their antibodies presumably would already have been identified. Possible reasons for their poor immunogenicity were identified.

Relationship between B-cell epitope structural properties and the immunogenicity of blood group antigens: Outlier properties of the Kell K1 antigen.

BACKGROUND: The immunogenicities of polypeptide blood group antigens vary, despite most being created by single amino acid (AA) substitutions. To study the basis of these differences, we employed an immunoinformatics approach to determine whether AA substitution sites of blood group antigens have structural features typical of B-cell epitopes and whether the extent of B-cell epitope properties is positively related to immunogenicity. STUDY DESIGN AND METHODS: Fifteen structural property prediction programs were used to determine the likelihood of ß-turns, surface accessibility, flexibility, hydrophilicity, particular AA composition and AA pairs, and other B-cell epitope properties at AA substitution sites of polypeptide blood group antigens. RESULTS: AA substitution sites of Lua , Jka , E, c, M, Fya , C, and S were each located in regions with at least two structural features typical of B-cell epitopes. The substitution site of K, the most immunogenic non-ABO/D antigen, scored the lowest for most B-cell epitope properties and was the only one not predicted to be part of a linear B-cell epitope. The most immunogenic antigens studied (K, Jka , Lua , E) had B-cell epitope structural properties determined by the fewest programs; the least immunogenic antigens (e.g., Fya , S, C, c) had B-cell epitope properties according to the most programs. DISCUSSION: Counter to prediction, the immunogenicity of polypeptide blood group antigens was not positively related to B-cell epitope structural features present at their AA-substitution sites. Instead, it tended to be negatively related. The AA-substitution site of the most immunogenic non-ABO/D antigen, K, had the least B-cell epitope features.

The University of Limerick Education and Research Network for General Practice (ULEARN-GP): practice characteristics and general practitioner perspectives.

BACKGROUND: A well-functioning general practice sector that has a strong research component is recognised as a key foundation of any modern health system. General practitioners (GPs) are more likely to collaborate in research if they are part of an established research network. The primary aims of this study are to describe Ireland's newest general practice-based research network and to analyse the perspectives of the network's members on research engagement. METHOD: A survey was sent to all GPs participating in the network in order to document practice characteristics so that this research network's profile could be compared to other national profiles of Irish general practice. In depth interviews were then conducted and analysed thematically to explore the experiences and views of a selection of these GPs on research engagement. RESULTS: All 134 GPs responded to the survey. Practices have similar characteristics to the national profile in terms of location, size, computerisation, type of premises and out of hours arrangements. Twenty-two GPs were interviewed and the resulting data was categorised into subthemes and four related overarching themes: GPs described catalysts for research in their practices, the need for coherence in how research is understood in this context, systems failures, whereby the current health system design is prohibitive of GP participation and aspirations for a better future. CONCLUSION: This study has demonstrated that the research network under examination is representative of current trends in Irish general practice. It has elucidated a better understanding of factors that need to be addressed in order to encourage more GPs to engage in the research process.

Relationship of epitope glycosylation and other properties of blood group proteins to the immunogenicity of blood group antigens.

BACKGROUND: The intrinsic properties of polypeptide blood group antigens that determine their relative immunogenicities are unknown. Because size, composition, charge, dose, and epitope glycosylation affect the immunogenicity of other polypeptides, we examined whether similar properties were related to the immunogenicity of blood group antigens. STUDY DESIGN AND METHODS: Amino acid (AA) sequences of antithetical blood group antigens were searched for N- and O-glycosylation sites. Regression analysis was carried out to determine whether blood group protein properties, including total and ectodomain size, red blood cell (RBC) antigen site density, number of mismatched AAs between an antigen and its closest homolog, and differences in mass, charge, and hydrophobicity of the mismatched AAs, were related to immunogenicity. RESULTS: The immunogenicities of non-RhD polypeptide antigens were directly related to the total and ectodomain sizes of their carrier proteins. A negative power relationship existed between RBC antigen site density and immunogenicity, such that the most immunogenic antigens had the lowest site density. The strong immunogenicity of RhD was related to the number of AA mismatches between RhD and RhCE, to their cumulative hydrophobicity and electrostatic mismatch scores, and the cumulative AA mass difference. No N- or O-glycosylation differences were predicted for antithetical or homologous antigens, other than a previously known N-glycosylation difference between K and k. CONCLUSION: Epitope glycosylation appeared not to be a determinant of immunogenicity for blood group antigens, except possibly for K. The immunogenicity of blood group antigens was positively related to total and ectodomain sizes of blood group proteins and negatively related to antigen site density. Such findings should be considered hypothesis generating for future, more definitive studies.

Structural and functional impacts of amino acid substitutions that create blood group antigens: implications for immunogenicity.

BACKGROUND: The immunogenicities of polypeptide blood group antigens vary widely. One possible determinant of immunogenicity is antigenic foreignness. The goal was to employ alternative ways of assessing foreignness and determine whether foreignness was related to immunogenicity. STUDY DESIGN AND METHODS: Foreignness was assessed as the extent of protein functional disruption caused by the exofacial amino acid (AA) substitutions that create blood group antigens, using AA substitution prediction algorithms such as Meta-SNP and according to whether those substitutions were radical or conservative. RESULTS: AA substitutions that create the most immunogenic antigens had the highest Meta-SNP scores, predictive of greater protein structure and function changes. Four of the 11 exofacial AAs that distinguish the most immunogenic antigen, RhD, from RhCE, and substitutions creating four of the five next most immunogenic antigens had the highest Meta-SNP scores (0.293-0.649). Excluding the outlier Jka , the mean Meta-SNP score of the four most immunogenic non-RhD antigens (K, Lua , E, c) was 3.7-fold higher than the mean of the four least immunogenic (M, Fya , C, S), 0.459 versus 0.123 (p = 0.0026). Regression analysis revealed a relationship between immunogenicity and Meta-SNP score (R2 = 0.953). Actual protein functional disruption was predicted for the AA substitution creating the E antigen. An AA cluster at Positions 350, 353, and 354 of RhD was unique, containing radical substitutions according to two classification schemes and relatively high Meta-SNP scores (0.351-0.432). CONCLUSION: The immunogenicity of blood group antigens was related to the functional disruption caused by the AA substitutions that create the antigens, as measured by Meta-SNP score.

Estimating the immunogenicity of blood group antigens: a modified calculation that corrects for transfusion exposures.

Calculations of blood group antigen immunogenicity have been based on antigen and antibody frequencies in transfused populations, with the assumption of a single red blood cell (RBC) unit exposure per patient. Given that patients are usually transfused >1 RBC unit, antigen exposures will be greater than assumed, resulting in inaccurate immunogenicity calculations. As such, the goal of this study was to modify the calculation to correct for RBC exposures. To further improve accuracy, we used an empirically-derived immunogenicity for the reference antigen, K, in calculations of absolute immunogencity and eliminated anamnestic and pre-existing antibodies (i.e., antibodies induced outside the study site) from the calculation. Alloantibody numbers for the top 12 specificities and mean RBCs (MRBC) transfused per patient were obtained from the records of a hospital transfusion service. A revised immunogenicity calculation, incorporating a correction for MRBC, was developed. This correction resulted in up to a 4-fold increase in the immunogenicity of relatively high frequency antigens, with smaller increases for lower frequency antigens, yielding the following revised immunogenicity ranking: K>Jk(a) >Lu(a) >E>P1>c>M>Le(b) >C>Le(a) >Fy(a) >S. Use of an empirical value for K immunogenicity resulted in a 1·9-fold increase in absolute immunogenicities for all antigens. In summary, the calculation of blood group antigen immunogenicity has been further refined.

Detection rate of blood group alloimmunization based on real-world testing practices and kinetics of antibody induction and evanescence.

BACKGROUND: Failure to detect non-ABO blood group alloantibodies places patients at risk for hemolytic reactions. Suboptimal alloantibody detection could result from posttransfusion testing performed too early, too late, or not at all. Testing performed too early may precede antibody induction, while testing performed too late could miss antibodies that have evanesced. Taking these factors into account, our goal was to determine the percentage of alloantibodies detected with real-world testing practices. STUDY DESIGN AND METHODS: The alloantibody detection rate in a general hospital setting was determined based on the frequency and timing of antibody testing after red blood cell (RBC) transfusions and rates of antibody induction and evanescence. Intervals to follow up testing after RBC transfusions (n = 561 RBC units in 100 random patients) were determined retrospectively. Best-fit lines and equations for antibody induction and evanescence were computed on previously published data. RESULTS: Nearly half (271/561; 48.3%) of RBC infusions had either no follow-up antibody screen or testing too soon (<30 days) after transfusion to detect alloimmunization. Of the remaining RBC units, 10.3% (58/561) had follow-up testing 30 to 112 days posttransfusion, 28.7% (161/561) were followed up at more than 112 days, and 12.7% (71/561) were tested at both 30 to 112 days and more than 112 days. By inputting these timing data into best-fit line equations for antibody induction and evanescence, we calculated an alloantibody detection rate of 31.6%. CONCLUSION: Posttransfusion antibody testing was inadequately timed for optimal alloantibody detection. Real-world compatibility testing was predicted to detect less than one-third of non-ABO antibodies, thereby exposing patients to risks of mismatched transfusion.

Fluid motion and shear forces in platelet storage bags with different modes of agitation.

This study describes a new method for comparison of fluid motion and associated shear forces with various modes of platelet agitation. Fluid motion generated by flatbed, tumbler-type and circular platelet agitators was investigated. Trajectory tracings of polyethylene beads suspended inside platelet storage bags were used to calculate motion parameters. Mean particle speeds generated by flatbed agitation were approximately 25-fold greater than those generated by 3-rpm tumbler-type agitation, corresponding to a wall shear stress increase in approximately sevenfold for flatbed agitation. As such, flatbed agitation is more likely to contribute to shear-associated changes in platelets than other modes of agitation.

Platelet transfusion: a clinical practice guideline from the AABB.

BACKGROUND: The AABB (formerly, the American Association of Blood Banks) developed this guideline on appropriate use of platelet transfusion in adult patients. METHODS: These guidelines are based on a systematic review of randomized, clinical trials and observational studies (1900 to September 2014) that reported clinical outcomes on patients receiving prophylactic or therapeutic platelet transfusions. An expert panel reviewed the data and developed recommendations using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework. RECOMMENDATION 1: The AABB recommends that platelets should be transfused prophylactically to reduce the risk for spontaneous bleeding in hospitalized adult patients with therapy-induced hypoproliferative thrombocytopenia. The AABB recommends transfusing hospitalized adult patients with a platelet count of 10 × 109 cells/L or less to reduce the risk for spontaneous bleeding. The AABB recommends transfusing up to a single apheresis unit or equivalent. Greater doses are not more effective, and lower doses equal to one half of a standard apheresis unit are equally effective. (Grade: strong recommendation; moderate-quality evidence). RECOMMENDATION 2: The AABB suggests prophylactic platelet transfusion for patients having elective central venous catheter placement with a platelet count less than 20 × 109 cells/L. (Grade: weak recommendation; low-quality evidence). RECOMMENDATION 3: The AABB suggests prophylactic platelet transfusion for patients having elective diagnostic lumbar puncture with a platelet count less than 50 × 109 cells/L. (Grade: weak recommendation; very-low-quality evidence). RECOMMENDATION 4: The AABB suggests prophylactic platelet transfusion for patients having major elective nonneuraxial surgery with a platelet count less than 50 × 109 cells/L. (Grade: weak recommendation; very-low-quality evidence). RECOMMENDATION 5: The AABB recommends against routine prophylactic platelet transfusion for patients who are nonthrombocytopenic and have cardiac surgery with cardiopulmonary bypass. The AABB suggests platelet transfusion for patients having bypass who exhibit perioperative bleeding with thrombocytopenia and/or evidence of platelet dysfunction. (Grade: weak recommendation; very-low-quality evidence). RECOMMENDATION 6: The AABB cannot recommend for or against platelet transfusion for patients receiving antiplatelet therapy who have intracranial hemorrhage (traumatic or spontaneous). (Grade: uncertain recommendation; very-low-quality evidence).

Record fragmentation due to transfusion at multiple health care facilities: a risk factor for delayed hemolytic transfusion reactions.

BACKGROUND: Patients transfused at more than one health care facility face safety risks, because their transfusion record is fragmented. Blood group antibodies documented at one facility may be unknown to others. Because many antibodies are evanescent, access to prior antibody records is important for preventing incompatible transfusions and delayed hemolytic reactions. The study goal was to quantify multisite transfusion activity and its impact on antibody record accuracy. STUDY DESIGN AND METHODS: Patients (n = 100) undergoing hospital transfusion testing were surveyed to determine the locations and dates of any prior transfusions. Also, transfusion records were examined to determine whether patients (n = 200) known to be alloimmunized at one hospital had antibody testing done at another nearby hospital and, if so, how often the results were discrepant. RESULTS: Twenty-three percent (23/100) of patients undergoing type-and-screen testing reported receiving transfusions at 24 other facilities. Locations of transfusions that occurred elsewhere were 54.2% (13/24) at eight other in-state hospitals, 12.5% in bordering states, 20.8% in more distant states, and 12.5% during military service. Twenty-one percent (42/200) of patients known to be alloimmunized at one hospital had antibody test results on record at another nearby hospital. Antibody discrepancies were noted in 64.3% (27/42) of cases. The most common discrepancy was the failure of one facility to detect an antibody. CONCLUSION: Multisite transfusions were common. For patients seen at both of two nearby hospitals, antibody records were frequently discrepant. The findings support the need for interfacility sharing of transfusion records, particularly at the regional level.

Trends in antibiotic prescribing in primary care out-of-hours doctors' services in Ireland.

Background: Infections are a common reason for patient consultation in out-of-hours (OOH) doctors' services. Surveillance of antibiotic prescribing in OOH settings is important to develop tailored antimicrobial stewardship (AMS) interventions. Objectives: To evaluate antibiotic prescribing patterns in OOH services in the Cork Kerry region, Ireland to inform future AMS interventions. Methods: A retrospective, observational cohort study was conducted of all oral antibiotic prescriptions in OOH doctors' consultations between 1 December 2019 and 31 December 2021 in the region. Data were gathered on age, gender, date and time of consultation, consultation method (in person, remote), antibiotic and its indication. Data were analysed using Microsoft Excel v.2018 and SPSS v.28. Results: Overall, 17% (69 017 of 406 812) of the OOH doctors' consultations resulted in an antibiotic prescription during the study period. This varied from 31% of OOH consultations in December 2019 to less than 2% of OOH consultations in April 2020. Of the antibiotics prescribed, 21% were for children under 6 years old. Respiratory tract infections (RTIs) were the most common indication for antibiotics (59%). Amoxicillin was the most commonly prescribed antibiotic (40% of all prescriptions). Red (reserved) antibiotics accounted for 19% of all prescriptions. During the COVID-19 pandemic period of the study, 66% of 49 421 of antibiotic prescriptions were issued from remote consultations. Conclusions: Low antibiotic prescribing levels during the early stages of the pandemic were not sustained. Antibiotic prescriptions from remote consultations were common. A key opportunity for AMS is addressing the volume of antibiotic prescribing for RTIs, particularly in children.

Evidence from whole genome sequencing of aerosol transmission of SARS-CoV-2 almost 5 hours after hospital room turnover.

Experimental evidence suggests that Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) remains viable within aerosols with a half-life of approximately 3 hours; however, it remains unclear how long airborne SARS-CoV-2 can transmit infection. Whole genome sequencing during an outbreak suggested in-room transmission of SARS-CoV-2 to two patients admitted nearly 2 and 5 hours, respectively, after discharge of an asymptomatic infected patient. These findings suggest that airborne SARS-CoV-2 may transmit infection for over 4 hours, even in a hospital setting.

Correlation of a commercial platform's results with post-vaccination SARS-CoV-2 neutralizing antibody response and clinical host factors.

INTRODUCTION: The objective of this study was to describe the correlation between the commercially available assay for anti-S1/RBD IgG and protective serum neutralizing antibodies (nAb) against SARS-CoV-2 in an adult population after SARS-CoV-2 vaccination, and determine if clinical variables impact this correlation. METHODS: We measured IgG anti-S1/RBD using the IgG-II CMIA assay and nAb IC50 values against SARS-CoV-2 WA-1 in sera serially collected post-mRNA vaccination in veterans and healthcare workers of the Veterans Affairs Connecticut Healthcare System (VACHS) between December 2020 and January 2022. The correlation between IgG and IC50 was measured using Pearson correlation. Clinical variables (age, sex, race, ethnicity, prior COVID infection defined by RT-PCR, history of malignancy, estimated glomerular filtration rate (GFR calculated using CKD-EPI equation) were collected by manual chart review. The impact of these clinical variables on the IgG-nAb correlation was analyzed first with univariable regression. Variables with a significance of p < 0.15 were analyzed with forward stepwise regression analysis. RESULTS: From 127 sera samples in 100 unique subjects (age 20-93 years; mean 63.83; SD 15.63; 29% female; 67% White), we found a robust correlation between IgG anti-S1/RBD and nAb IC50 (R2 = 0.83, R2adj = 0.70, p < 0.0001). Race, ethnicity, and a history of malignancy were not significant on univariable analysis. GFR (p < 0.05) and prior COVID infection (p < 0.001) had a significant impact on the correlation between IgG anti-S1/RBD and nAb IC50. Age (p = 0.06) and sex (p = 0.07) trended towards significance on univariable analysis, but were not significant on multivariable regression. CONCLUSIONS: There was a strong correlation between IgG anti-S1/RBD and nAb IC50 after SARS-CoV-2 vaccination. Clinical comorbidities, such as prior COVID infection and renal function, impacted this correlation. These results may assist the prediction of post-vaccination immune protection in clinical settings using cost-effective commercial platforms.

Optimising the delivery of tubulin targeting agents through antibody conjugation.

Despite their side effect profile, there currently remains a heavy reliance on traditional cytotoxics and particularly tubulin targeting agents in cancer chemotherapy. To address this concern, significant progress has been made in the selective delivery of drugs to the tumour site. This review will examine the published data in support of the hypothesis that forming antibody conjugates of tubulin targeting agents is an effective approach towards their more effective delivery to the tumour site. Particular emphasis will be placed on the diversity of concepts under investigation, the efficacy of resultant conjugates, evidence of decreased resistance and the side effect profiles of the conjugates.

Selective Delivery of Clinically Approved Tubulin Binding Agents through Covalent Conjugation to an Active Targeting Moiety.

The efficacy and tolerability of tubulin binding agents are hampered by their low specificity for cancer cells like most clinically used anticancer agents. To improve specificity, tubulin binding agents have been covalently conjugated to agents that target cancer cells to give actively targeted drug conjugates. These conjugates are designed to increase uptake of the drug by cancer cells while having limited uptake by normal cells, thereby improving efficacy and tolerability. Approaches used include an attachment to small molecules, polysaccharides, peptides, proteins, and antibodies that exploit the overexpression of receptors for these substances. Antibody targeted strategies have been the most successful to date, with six such examples having gained clinical approval. Many other conjugate types, especially those targeting the folate receptor, have shown promising efficacy and toxicity profiles in pre-clinical models and in early-stage clinical studies. Presented herein is a discussion of the success or otherwise of the recent strategies used to form these actively targeted conjugates.

Clinical and virologic factors associated with outcomes of COVID-19 before and after vaccination among Veterans: Retrospective analysis from six New England states.

We aimed to characterize clinical and demographic factors affecting clinical outcomes of COVID-19 and describe viral epidemiology among unvaccinated Veterans in New England. Veterans infected with COVID-19 in Veterans Administration healthcare systems in six New England states from April 8, 2020, to September 2, 2021, were correlated with outcomes of 30-day mortality, nonpsychiatric hospitalization, and intensive care unit admission (ICU-care). We sequenced 827 viral genomes. Of 3950 Veterans with COVID-19 before full vaccination, 81% were White, 8% were women, and the mean age was 60 years. Overall, 19% of Veterans required hospitalization, 2.8% required ICU care, and 4.9% died. In this largely male and older cohort, poor outcomes correlated with increasing age. Most New England Veterans (>97%) were infected with B.1 sublineages with the D614G mutation in 2020 and early 2021. B.1.617.2 lineage (68%) predominated after July 2021.

Characterization of vabicaserin (SCA-136), a selective 5-hydroxytryptamine 2C receptor agonist.

The 5-hydroxytryptamine 2C (5-HT(2C)) receptor subtype has received considerable attention as a target for drug discovery, having been implicated in a wide variety of disorders. Here, we describe the in vitro pharmacological profile of the novel 5-HT(2C) receptor-selective agonist vabicaserin [(-)-4,5,6,7,9,9a,10,11,12,12a-decahydrocyclopenta[c] [1,4]diazepino[6,7,1-ij]quinoline hydrochloride] (SCA-136), including a comprehensive strategy to assess 5-HT(2B) receptor selectivity using diverse preparations and assays of receptor activation. Vabicaserin displaced (125)I-(2,5-dimethoxy)phenylisopropylamine binding from human 5-HT(2C) receptor sites in Chinese hamster ovary cell membranes with a K(i) value of 3 nM and was >50-fold selective over a number of serotonergic, noradrenergic, and dopaminergic receptors. Binding affinity determined for the human 5-HT(2B) receptor subtype using [(3)H]5HT was 14 nM. Vabicaserin was a potent and full agonist (EC(50), 8 nM; E(max), 100%) in stimulating 5-HT(2C) receptor-coupled calcium mobilization and exhibited 5-HT(2A) receptor antagonism and 5-HT(2B) antagonist or partial agonist activity in transfected cells, depending on the level of receptor expression. In rat stomach fundus and human colonic longitudinal muscle endogenously expressing 5-HT(2B) receptors, vabicaserin failed to induce a 5-HT(2B) receptor-dependent contraction and produced a rightward shift of the 5-HT and α-methyl-5-HT concentration-response curves in these preparations, respectively, consistent with 5-HT(2B) competitive antagonism. Likewise, vabicaserin failed to induce a 5-HT(2B) receptor-mediated contraction in arteries from deoxycorticosterone acetate-salt-treated rats, a model of hypersensitized 5-HT(2B) receptor function, and produced a rightward shift in the 5-HT-induced response that was consistent with 5-HT(2B) receptor antagonism. In summary, vabicaserin is a novel, potent, and selective 5-HT(2C) receptor agonist.

Immunogenicity of blood group antigens: a mathematical model corrected for antibody evanescence with exclusion of naturally occurring and pregnancy-related antibodies.

Blood group antigen immunogenicity is a crucial factor in red blood cell alloimmunization. Previous calculated estimates of immunogenicity suffered from several key shortcomings. To address these issues we have (1) introduced a correction factor for antibody persistence rates into traditional immunogenicity calculations, (2) calculated immunogenicities only in men to eliminate pregnancy-related antibodies, and (3) excluded antibodies reactive only at room temperature to minimize the contribution of naturally occurring antibodies. With these corrections, we have calculated the immunogenicities of common blood group antigens using data collected on clinically significant alloantibodies (n = 452) in a male patient population. We observed a 3- to 5-fold increase in immunogenicity for some antigens (ie, Jk(a), C(w), Lu(a)) and smaller changes in others compared with traditionally calculated estimates. In addition, we have calculated the transfusion-related immunogenicities of antigens traditionally associated with naturally occurring antibodies (eg, anti-Le(a), -Le(b), -M, and -P(1)).