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Background: This study aims at identifying the microbiota in traumatized immature permanent teeth with periapical lesions using Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS)., Methods: The study included 16 immature maxillary central incisors with periapical lesions in 13 patients. Field decontamination and negative control samples were performed before and after access cavity preparation. Root canal samples were taken using sterile stainless-steel hand files following field decontamination. In-office inoculation and pure sub-cultures were performed. Bacterial isolates were prepared for MALDI-TOF MS (Bruker, Billerica, MA USA) analysis using the formic acid extraction method. A comparison of the prevalence of isolated microorganisms was done using a one-sample chi-square test. Comparisons between identified microbial species with the, cone beam computed tomography periapical index (CBCT PAI) scores and lesion volume were also conducted. The Chi-square test was applied to investigate the association between the categorical variables ., Results: Out of the forty isolates recovered from the 16 traumatized teeth included in the present study with the mean patients' age of 10.93 ± 1.77, 37 isolates were reliably identified by MALDI-TOF MS. Twelve teeth (62.5%) were polymicrobial. The recovered bacteria belonged to five phyla, 15 genera and 25 species. Firmicutes were the predominant phylum (P < 0.001) over Bacteroidetes, Proteobacteria, Actinobacteria and Fusobacteria. Gram positive bacteria were significantly more prevalent than Gram negative (p = 0.03). Facultative anaerobes were the most prevalent (P < 0.001) compared to the obligate anaerobes and the obligate aerobes. The latter were the least prevalent. Statistically, significant differences existed in the comparison between CBCT PAI scores according to bacterial gram staining., Conclusion: Traumatized immature permanent teeth with periapical lesions showed a significant predominance of Gram-positive facultative anaerobes. MALDI-TOF MS provided accurate identification of numerous viable endodontic microbes., (© 2022. The Author(s).)

Background: Exposure to organic solvents (OS) adversely affects different body systems, the central and peripheral nervous systems being the most susceptible ones., Objectives: This study investigated the role of iron in association with some neurotransmitters for diagnosis of neurotoxicity of OS., Methods: The study included 90 workers, 50 occupationally exposed to OS and 40 representing control group. Blood samples were collected from the included subjects for determination of serum iron, total iron binding capacity (TIBC), serotonin and gamma-aminobutyric acid (GABA)., Results: Revealed reduction in serotonin level and serum iron. However, the elevation in GABA and TIBC was observed. The duration of exposure was significantly correlated with iron and serotonin while it was positively correlated with GABA and TIBC., Conclusions: Elevated GABA and TIBC with decreased serotonin and serum iron can be used as early diagnostic measures to detect the neurotoxic effects of OS., (© 2021 Walter de Gruyter GmbH, Berlin/Boston.)

The goal of the present study is to estimate the oxidative effects of AFB1 induced hepatotoxicity in furniture wood dust exposed workers. A cross-sectional comparative study was designed for comparing AFB1/albumin (AFB1/alb) levels and liver functions [alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP)], malondialdehyde (MDA), glutathione peroxidase (GPx), catalase (CAT) and superoxide dismutase (SOD) in 88 furniture workers and 78 controls not occupationally exposed to wood dust. The AFB1/Alb, AST, ALT, MDA, and GPx were significantly higher; while, CAT significantly reduced in workers compared with controls. There was a significant correlation between AFB1/Alb and MDA level with the liver enzymes among both groups. CAT was inversely correlated with AFB1/Alb and the liver enzymes, and GPx was inversely correlated with AST in the workers. It was concluded that wood dust exposure is associated with raised serum levels of AFB1 and oxidative stress.

Background: Recently, the interleukin-17A ( IL-17A ) gene has emerged as a potential candidate gene for autoimmune disorders, including systemic lupus erythematosus (SLE)., Objectives: This study aimed to investigate whether IL-17A polymorphisms at rs2275913 G/A, rs8193036 C/T and rs3748067 C/T could be susceptibility markers for juvenile-onset SLE (JSLE) and lupus nephritis (LN) in Egyptian children and adolescents., Methods: In this multi-centre study, we genotyped 320 patients diagnosed with JSLE and 320 matched control children for three IL-17A polymorphisms at rs2275913 G/A, rs8193036 C/T and rs3748067 C/T using TaqMan probe-based real-time polymerase chain reaction. Meanwhile, IL-17A serum levels were assessed using ELISA., Results: The IL-17 rs2275913 A/A genotype and A allele were more represented in JSLE patients compared to the control group (21% vs. 7%, odds ratio (OR) = 3.8, 95% confidence interval (CI) 1.78-5.5, p  = 0.001, p Bonf = 0.003 for the A/A genotype; 37% vs. 29%, OR = 1.4, 95% CI 1.11-1.8, p  = 0.003, p Bonf = 0.009 for the A allele. No significant difference was found for IL-17 rs8193036 and rs3748067 single nucleotide polymorphisms (SNPs) in genotype distribution or allele frequencies ( p >0.05). Patients carrying the IL-17 rs2275913 A/A genotype and A allele were more likely to develop LN (OR = 5.64, 95% CI 2.39-13.77, p Bonf = 0.001 for the A/A genotype; OR = 2.73, 95% CI 1.84-4.07, p Bonf = 0.02 for the A allele)., Conclusion: The IL-17 rs2275913 A allele and A/A genotype were associated with high IL-17 serum levels and may contribute to susceptibility to JSLE and the development of LN in Egyptian children and adolescents. However, no significant association was evident between the studied IL-17A SNPs and other clinical phenotypes, disease activity scores or laboratory profile of JSLE.

Background: Pneumonia is the foremost cause of child death worldwide. M-ficolin is encoded by the FCN1 gene and represents a novel link between innate and adaptive immunity., Objectives: To investigate the FCN1 -144 C/A (rs10117466) polymorphism as a potential marker for pneumonia severity and adverse outcome namely complications or mortality in the under-five Egyptian children., Methods: This was a prospective multicenter study that included 620 children hospitalized with World Health Organization-defined severe pneumonia and 620 matched healthy control children. Polymorphism rs10117466 of the FCN1 gene promoter was analyzed by PCR-SSP, while serum M-ficolin levels were assessed by ELISA., Results: The FCN1 A/A genotype and A allele at the -144 position were more frequently observed in patients compared to the control children (43.4% vs 27.6%; odds ratio [OR]: 1.62; [95% confidence interval {CI}: 1.18-2.2]; for the A/A genotype) and (60.8% vs 52.5%; OR: 1.4; [95% CI: 1.19-1.65]; for the A allele); P < .01. The FCN1 -144 A/A homozygous patients had significantly higher serum M-ficolin concentrations (mean: 1844 ± 396 ng/mL) compared with those carrying the C/C or C/A genotype (mean: 857 ± 278 and 1073 ± 323 ng/mL, respectively; P = .002). FCN1 -144 A/A genotype was an independent risk factor for adverse outcomes in children with severe pneumonia (adjusted OR = 4.85, [95% CI: 2.96-10.25]; P = .01)., Conclusion: The FCN1 A/A genotype at the -144 position was associated with high M-ficolin serum levels and possibly contributes to enhanced inflammatory response resulting in the adverse outcome of pneumonia in the under-five Egyptian children., (© 2020 Wiley Periodicals, Inc.)

Background: Coke oven workers are exposed to polycyclic aromatic hydrocarbons (PAHs) with possible genotoxicity and carcinogenicity. Metabolizing enzymes genes and DNA repair genes are suspected to be correlated with the level of DNA damage. They may contribute to variable individual sensitivity to DNA damage induced by PAHs exposure at workplace., Objective: To investigate the relationship between biomarkers of PAHs: 1-hydroxypyrene (1-OHP), DNA adducts, and 8-hydroxy-2-deoxyguanosine (8-OHdG) in coke oven workers, and to assess the role of cytochrome P2E1 (CYP2E1) gene expression and DNA repairing gene (XRCC1) polymorphism in detecting workers at risk., Methods: 85 exposed workers and 85 unexposed controls were enrolled into this study. Urinary 1-OHP, 8-OHdG, and BPDE-DNA adduct were measured. CYP2E1 gene expression and genotyping of XRCC1 399 Arg/Gln were evaluated by real-time PCR., Results: The median urinary 1-OHP levels (6.3 μmol/mol creatinine), urinary 8-OHdG (7.9 ng/mg creatinine), DNA adducts (6.7 ng/μg DNA) in the exposed group were significantly higher than those in the unexposed group. Carriers of the variant allele (Gln) of XRCC1 had the highest levels of 1-OHP, DNA adducts and 8-OHdG, and the lowest level of CYP2E1 gene expression. In exposed workers, significant positive correlations were found between 1-OHP level and each of the work duration, 8-OHdG, and DNA adducts levels. There was a significant negative correlation between 1-OHP level and CYP2E1 gene expression. Work duration and CYP2E1 gene expression were predictors of DNA adducts level; 1-OHP level and work duration were predictors of urinary 8-OHdG level., Conclusion: Workers with higher exposure to PAH were more prone to oxidative DNA damage and cancer development. DNA adducts level reflects the balance between their production by CYP2E1 and elimination by XRCC1 gene.

Aim: The study aimed to assess worksite health education workshops as a successful tool for health promotion of employees., Material and Methods: A one day workshop was held for individuals engaged in research activities in the National research Centre of Egypt at the worksite. Its main objective was to highlight the nature, causes, symptoms and management of job stress. Participants were asked to fill a personality assessment sheet, a self-reported questionnaire for job satisfaction. Other questionnaires for assessment of falsification of type and some socio-demographic data were filled by the attendants. A concise survey was introduced at the end of the workshop for feedback collection., Results: Attendants of the workshop were 36 subjects mainly females (94.4%). Mean age was 40.5 years with 63.9% of participants at their postdoctoral studies stage. Participants were at midway in the scale of job satisfaction (3.3) and did not suffer from falsification (0.3). The feedback survey score (11.5) showed great acceptance for the intervention. Special interest in the topic of stress was reported by 35.1% of attendants who found it the best item in the workshop and the interactive manipulation came next as declared by 18.9% of the participants., Conclusion: Worksite health education workshops seem to be a successful practice for empowerment in the Egyptian workplace.

Aim: The study aimed to investigate effects of organic dust exposure from different sources on aflatoxin B1-albumin adducts (AFB1/Alb), and role of glutathione S-transferase (GST) gene polymorphism in hepatotoxicity of (AFB1) among exposed workers., Material and Methods: Liver enzymes, AFB1/Alb, and GST polymorphism were estimated in 132 wheat flour dust and 87 woods sawmill workers, and 156 controls., Results: Results revealed that AFB1/Alb and liver enzymes were significantly elevated in exposed workers compared to controls, and were significantly higher in sawmill workers compared to flour workers. AFB1/Alb in flour and sawmill workers with GSTT1 and GSTM1&GSTT1 null genotypes were significantly higher than controls, and in sawmill workers with GSTM1&GSTT1 null than flour workers. Liver enzymes (ALT and AST) in sawmill workers were significantly higher than flour workers and controls in all GST polymorphism; except in GSTT1 polymorphism, where these enzymes were significantly higher in the two exposed groups than controls., Conclusions: In conclusion, organic dust exposure may cause elevation in AFB1/Alb and liver enzymes of exposed workers, and GST gene polymorphism plays an important role in susceptibility to hepatic parenchymal cell injury; except in workers with GSTT1&GSTM1 null genotype, gene susceptibility seemed to have little role and the main role was for environmental exposures.

Streptococcus pneumoniae is a major cause of childhood morbidity and mortality worldwide with increasing antimicrobial resistance. 600 randomly chosen asymptomatic healthy children aged 2-60 months attending Alexandria University Children's Hospital were evaluated for prevalence of nasopharyngeal (NP) carriage of S. pneumoniae. Prevalence of NP carriage was 29.2% (n = 175/600) Capsular serotyping was done using Quellung reaction. Vaccine covered serotypes (VST) represented 67.4% while non-vaccine serotypes (NVST) were 32.6%. The most common VST isolated were 19F (24.6%), 6B (14.3%) and 6A (10.9%). Confirmation of serotyping was performed by multiplex PCR which showed 100% concordance with the Quellung reaction. Antimicrobial susceptibility testing showed penicillin non-susceptibility of 15% (using non-meningitis penicillin MIC breakpoints) and 55% (using meningitis penicillin MIC breakpoints). Highest resistance was found in sulphamethoxazole-trimethoprim (55%), tetracyclins (49%), erythromycin (40%) and clindamycin (25%). This study revealed the epidemiological importance to evaluate regularly the prevalence, serotypes and the increasing antimicrobial resistance of S. pneumoniae in the community., (© The Author [2015]. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Objective: To measure the impact of an antimicrobial stewardship (AMS) program on the use of antibiotics for surgical prophylaxis at acute care hospitals in Egypt., Methods: This was a before-and-after intervention study conducted in 5 tertiary, acute-care surgical hospitals. The baseline, intervention, and follow-up periods were 3, 6, and 3 months, respectively. The impact of the intervention was measured by preintervention and postintervention surveys for surgical patients with clean and clean-contaminated wounds. Information was collected on demographic characteristics and antibiotic use. The intervention focused mainly on educating surgical staff on the optimal timing and duration of antibiotics used for surgical prophylaxis. Only 3 hospitals identified a surgeon to audit antibiotic surgical prescriptions. The primary outcome measures were the percentages of surgical patients receiving optimal timing and duration of surgical prophylaxis., Results: Data were collected for 745 patients before the intervention and for 558 patients after the intervention. The optimal timing of the first dose improved significantly in 3 hospitals, increasing from 6.7% to 38.7% (P < .01), from 2.6% to 15.2% (P < .01), and from 0% to 11% (P < .01). All hospitals showed a significant rise in the optimal duration of surgical prophylaxis, with an overall increase of 3%-28% (P < .01). Days of therapy per 1000 patient-days were decreased significantly in hospitals A, B, C, and D, with no change in hospital E., Conclusions: An AMS program focusing on education supported by auditing and feedback can have a significant impact on optimizing antibiotic use in surgical prophylaxis practices., (Copyright © 2015 Association for Professionals in Infection Control and Epidemiology, Inc. All rights reserved.)

Aluminum (Al) metal is considered one of the most benign industrial metals. Although the harmful effects of Al on respiratory health have been denied by some studies, others reported its noxious effect on the lung through spirometric measurements. This work aimed at studying the effect of Al fumes on pulmonary functions of occupationally exposed workers. It investigated the possible relationship between inhalation exposure to Al fumes and levels of C-reactive protein (CRP) and alpha-1-antitrypsin (A1AT). The study participants comprised a group of 56 male Al workers with a mean duration of occupational exposure of 10.1 ± 9.5 years and 52 male participants who were not exposed to Al fumes as the control group. All participants filled a questionnaire, underwent full clinical examination and their spirometric pulmonary functions were measured. Blood samples were collected for the determination of serum CRP and A1AT and urine samples for measuring Al. Results revealed that urinary Al (UAl) was significantly higher in Al workers compared with controls (p < 0.05). However, spirometric measures showed no significant difference between the exposed group and the controls. A1AT was significantly lowered in Al workers compared with the controls (p < 0.000). Serum CRP was positive in only two (3.6%) of the exposed workers. Smokers of both groups (exposed and controls) showed significantly higher UAl and lower A1AT compared with nonsmokers. There was only significant negative correlation between the duration of exposure and A1AT (p < 0.05). There was a positive significant correlation between smoking index (SI) and UAl. There was also significant negative correlation between SI and some of the pulmonary function tests namely the percentage of predicted forced vital capacity, forced expiratory volume in the first second and peak expiratory flow in the exposed group. Those correlations point to the importance of the combined effect of smoking and Al exposure on the impairment of lung functions. The study recommends the determination of CRP and A1AT in Al-exposed workers. It is expected that those parameters may undergo changes before reduction in pulmonary functions takes place., (© The Author(s) 2012.)

Background: Early detection of multidrug-resistant Mycobacterium tuberculosis (MDR-TB) is of primary importance for both patient management and infection control. Optimal methods for identifying MDR-TB in a timely and affordable manner in resource-limited settings are not yet available., Objectives: To evaluate the performance of a low-technology but rapid drug susceptibility testing method, the microscopic observation drug susceptibility assay (MODS), in the concurrent detection of M. tuberculosis and its susceptibility to isoniazid (INH) and rifampin (RMP) directly from sputum specimens., Methods: A total of 115 smear-positive TB patients admitted to Abbasia Chest Hospital, Cairo, Egypt, were simultaneously tested using MODS and the BACTEC MGIT 960 mycobacterial detection system for the detection of M. tuberculosis and the identification of MDR-TB samples., Results: MODS detected 112 (97.4%) samples and BACTEC MGIT detected 115 (100%). Of the 115 isolates tested for susceptibility to INH, RMP and MDR-TB, complete agreement between MODS and MGIT results was found among respectively 92.9%, 95.5% and 97.3% of samples. The sensitivity, specificity, and positive and negative predictive values of MODS in the detection of MDR-TB were respectively 95.3%, 98.6%, 97.6% and 97.1%. MODS results were obtained in a median of 8 days (range 5-21)., Conclusion: MODS is an optimal alternative method for timely and affordable identification of MDR-TB in resource-limited settings.

Background: Nosocomial bloodstream infections (BSIs) and antimicrobial resistance (AMR) are worldwide health care problems causing substantial patient morbidity and mortality. This study was conducted to identify bacterial pathogens isolated from nosocomial BSIs and determine their AMR patterns., Methods: An active surveillance program for BSIs was conducted in intensive care units in 3 large university hospitals in Egypt between September 1, 2006, and June 30, 2007. Infection prevention and control teams and link nurses in collaboration with intensive care physicians were looking actively to identify patients who acquired BSIs based on Centers for Disease Control and Prevention standard case definitions. Blood cultures were obtained from patients with suspected BSIs and processed to isolate bacteria and test their antimicrobial resistance., Results: During the 10-month active surveillance period, a total of 600 pathogens were isolated from blood cultures of 1,575 patients (38%). Of these 600 isolates, 386 (66%) were gram-negative, 178 (30%) were gram-positive, and 24 (4%) were budding yeasts. The gram-negative organisms included 162 (27%) Klebsiella pneumoniae and 23 (3.8%) Escherichia coli. Extended-spectrum β-lactamase enzymes were detected in 79% of the K pneumoniae isolates and 39% of the E coli isolates. Methicillin-resistant Staphylococcus aureus accounted for 60% of S aureus infections., Conclusions: High rates of β-lactamase resistance and methicillin-resistant S aureus were found in the 3 Egyptian university hospitals studied. This study highlights the need for strengthening infection prevention and control programs, monitoring AMR at each facility, and developing policies for antibiotic use., (Published by Mosby, Inc.)

Fifty HCWs in ICUs of Internal medicine, Chest, Neonatology and Burn were included in prospective cohort study. Collection of nasal, hand and rectal swabs, proper biochemical identification, culture media and antibiotic sensitivity tests were used to detect Methicillin-resistant Staphylococcus aureus (MRSA); vancomycin-resistant Enterococci (VRE) & extended spectrum beta-lactamase producing gram -ve bacilli (ESBLs). S. aureus was isolated from 34% of HCWs; 28% were nasal carriers, 4% were hand carriers and 2% had S. aureus at both sites. Nasal and hand carriage rates of MRSA were 20% & 4% respectively, with an overall rate of 22%. Gram -ve bacilli were isolated from 8% of HCWs hand swabs & showed Citrobacter koseri, Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa. Hand carriage rate of ESBLs was 2%. Hand contamination with gram -ve bacilli and S. aureus was in 14% of HCWs. VRE carriage rate was 9.5%. ESBLs carriage rate in rectal swabs was 21.43%. K. pneumoniae was the most common ESBLs producing isolate (33.3%), followed by E. coli (18.75%). In combined disc method, aztreonam was the most sensitive (90%) in detecting ESBLs. Burn ICU had highest % of MRSA & ESBLs carriage. Neonatal ICU showed highest % of VRE carriage. An insignificant association was between infection control training or antimicrobial intake and carriage of antimicrobial resistant bacteria.

Atopic dermatitis (AD) is a complex immunologic skin disorder that is expressed when genetically predisposed individuals are exposed to certain environmental stimuli. Inspite of the high prevalence of cytomegalovirus (CMV) infection and its potent immunomodulatory activities, the relation of CMV to AD is still poorly understood and is still to be clarified. The aim of the present study was to evaluate the frequency of active CMV infection in patients with AD and its possible etiologic role in the pathogenesis of the disease. Also, we tried to find if a relation between active CMV infection and disease severity exists. The present study was carried on 31 patients with AD with various degrees of disease severity. Ten apparently healthy subjects were enrolled in the study as a control group. Anti CMV IgG antibodies were estimated by quantitative enzyme immunoassay to discriminate between recent CMV infection and CMV reactivation. Active CMV infection was diagnosed by using nested PCR to detect CMV DNA in the sera of the studied subjects. The detection rate of CMV genome was higher in patients with AD in comparison to the control group. Cytomegalovirus genome was detected in the sera of 52% (16/31) of patients with AD (87.5% of them were seropositive for anti-CMV IgG antibodies). On the other hand no CMV DNA was detected in any of the serum samples of the control subjects. The difference was statistically significant. No significant relation was found between active CMV infection and disease severity. Also, no significant statistical difference was found between the two studied groups as regards the prevalence of latent CMV infection. In addition, no significant difference was detected between anti-CMV IgG antibody levels in all seropositive subjects. Our results denote that active subclinical CMV infection is more frequent in patients with AD and may have possible immunomodulatory role in the etiopathogenesis of AD but it is not related to disease severity.

Perennial allergic rhinitis (PAR) is an increasing problem for which new and exciting therapies are being developed. A T(H)2-polarized cytokine pattern is thought to predominate regulating local IgE synthesis and cell recruitment in PAR and the development of intranasal steroids has resulted in several agents with quick actions, localized effects and great efficacy in its management. The aim of work was to determine the differences in the local expression of IL-4 and IL-5 in patients with PAR compared to non-atopic healthy controls and investigate the relationship between the expression of these cytokines and the clinical aspects of the disease. Also to evaluate local expression of these cytokines in some of these patients before and after treatment with intranasal steroids (fluticasone proprionate). Nasal biopsies from 37 patients with PAR before therapy and from 8 of them after receiving corticosteroids as local nasal spray were taken. PAR was confirmed by a history of perennial nasal blockage, discharge, and/or sneeze for at least 2 years before the study and by positive skin prick test. Also nasal biopsies were taken from 20 age and gender matched non-atopic controls. Biopsies were analyzed using a reverse transcription-polymerase chain reaction (RT-PCR) to investigate local expression of IL-4 mRNA. Enzyme immunoassay was used for estimation of IL-5 levels in the nasal mucosa. By using the ROC curve; (11 pg/ml) was estimated as a cut-off value for IL-5 where levels below this cut off were considered negative. This study showed that the most common causative allergens in PAR were mite dust, followed by wool & pigeon then mixed moulds. There was a significant relation between expression of IL-4 and IL-5 and the occurrence of allergic rhinitis where mRNA of IL-4 was detected in 17/37 [46%] of patient group and in 3/20 (15%) of the control group (P < 0.05). IL-5 levels were more than the calculated cut off value in 22/37 (59.5%) of patient group as compared to 4/20 (20%) in the control group (P < 0.01). Also a high significant association was found between IL-4 & IL-5 (P < 0.01) in patient group. However, no significant relation was found between signs & symptoms of AR or patients' age or gender and cytokines expression. Corticosteroid nasal spray treatment showed a significant reduction in IL-4 gene expression and IL-5 positivity (P < 0.05). It is concluded that IL-4 & IL-5 have an important role in the pathogenesis of PAR and corticosteroid nasal spray is effective in exerting an immunomodulatory activity by reducing IL-4 & IL-5 expression.

We studied five different tests for diagnosing conjunctival Chlamydia trachomatis infection in specimens obtained from 100 children with moderate-to-severe trachoma. The tests were Giemsa stain, isolation in cell culture, direct fluorescein-conjugated monoclonal antibody, enzyme immunoassay, and a DNA probe. The Giemsa stain was least sensitive at 29%. The other tests gave essentially equivalent performances: sensitivity ranged from 73% to 84% and specificity from 93% to 100%. Seven of the 45 positive specimens were only positive in cell culture, whereas 11 of the 45 were negative in culture but positive in at least two nonculture tests. We speculate that these discordant results actually reflect the biologic status of the chlamydial infection. There appears to be a stage in the infection where chlamydial antigens and nucleic acids can be detected in the absence of infectivity. This stage of infection may contribute to the pathogenesis of trachoma by providing a source of sensitizing antigen.