Serum incubation of monoclonal antibodies chelate labeled by DPTA, benzyl-EDTA and benzyl-TETA with 111 In, 57 Co, and 67 Cu demonstrated marked differences in their stability. Enzyme-Linked Immunosorbent Assay 4.

The stability in human serum is an important factor affecting the therapeutic efficacy of antibodies, so it is quite meaningful to analyze the in vitro serum stability of BsAbs. Test Code SEBV Epstein-Barr Virus (EBV) Antibody Profile, Serum Reporting Name Specimen Stability Information. Hospital (Cerner) Order Code .

Add On Capable.

its specificity and affinity). Test result agreement with

DiaSorin Liaison Chemiluminescet Immunoassay. However, due to possible reflex testing, please draw 3.0 ml blood minimum (1.5 ml Serum) Collection Instructions: Gently invert sample 5-6 times after collection. Assay stability .

For long-term storage, we recommend storing serum vials and aliquots of purified antibody at -20C.

In -20C or -80C, serum can usually be stored for years. Patient Preparation: For 12 hours before specimen collection do not take multivitamins or dietary supplements containing biotin (vitamin B7), Specimen Stability Information. Specimen Stability Information.

Supplies: Aliquot Tube, 5 ml (T465) Specimen Type: Plasma/Blood.

(IFA), and Western blot (WB) for detecting anti-HIV antibodies. Fluorescent Antibody Technique 3.

In some cases, more careful freezing with a first step at -20C, followed by -70C is beneficial.

-Differential diagnosis of etiology of thyrotoxicosis in patients with ambiguous clinical findings and/or contraindicated (eg, pregnant or breast-feeding) or nondiagnostic thyroid radioisotope scans. In this regard, chicken antibodies, like rabbit and mouse antibodies, will lose some biological activity (typically about 50%) upon freezing. Name Units Reference Range Conversion Factor; Acetylcholine Receptor Antibodies: nmol/L: Negative: <0.40 Interpretation. Radioimmunoassay 5.

It is the repository of almost all of the active hormones, T3 and T4, within the gland. Heat-inactivation can also interfere with Western blot analysis (8).

Test Code SHSTO Histoplasma Antibody, Serum Additional Codes. Immobilization Can Improve the Stability of Hybridoma Antibody Productivity in Serum-Free Media Gyun Min Lee and Bernhard 0.

The stability over time of serum IgG antibody levels to human papillomavirus type 16 (HPV-16) was determined by comparing the HPV-16 capsid antibody levels in serial serum samples of

Negative: No IgG antibodies to Schistosoma species detected.. Equivocal: Recommend follow-up testing in 10 to 14 days if clinically indicated.

Test Code TGAB Thyroglobulin Antibody, Serum Serum or HTGR / Thyroglobulin, Tumor Marker Reflex, Serum. Further (serial fivefold) dilutions are performed, each of which contain less and less serum.

reported that modulation of the pK a of the thiol of a cysteine residue could aect the stability of ADCs.

Specimen Type Temperature Time Special Container; Serum Red: Refrigerated (preferred) 7 days : Contribute to light in serum samples for homologous protein that the antibody present in binding activity occurs slowly over small. Specimen Type: Serum.

A small amount of IgA is also secreted into the serum in monomeric form. Container/Tube: Red top (gel tubes/SST are not acceptable) Specimen Volume: 0.6 mL. Each winter, approximately 10-20% of the population are infected. SS-A/Ro antibodies Specimen Type Temperature Time Special Container; Serum: Refrigerated (preferred) 14 days : Frozen : 14 days: Reference Values.

Table 2.

Ab, S. Methodology. AS, BSF, and, HSF samples were maintained at pH 7.4 by incubating at 37 C and 6.5% CO 2.

Therefore, you should avoid diluting antibodies to working concentration and keeping them at 4C for more than a day. Epic Order Name: HISTOPLASMA AB Specimen Stability Information. When used for diagnosis, it is recommended that specific tests for proteinase 3 (PR3) ANCA and myeloperoxidase (MPO) ANCA be performed in addition to testing for cANCA and pANCA. A total of 200 prospective serum samples submitted for dengue virus (DV) IgM and IgG testing by the Focus Diagnostics DV IgM and IgG EIAs were also tested by the InBios IgM and IgG DV assays.

stability and ecacy.10,11 Vollmar et al. In this work, we review the different mechanisms that can be linked to monoclonal antibodies instability, the parameters, and conditions affecting their stability (protein structure and concentration, temperature, interfaces, light exposure, excipients and

Test Code TGABI Thyroglobulin Antibody, Serum Serum.

Test ID ACMFS Acetylcholine Receptor Modulating Antibody, Flow Cytometry Assay, Serum (MuSK) Reflex, Serum is the testing of choice in most cases.

Here, the European Bioanalysis Forum (EBF) reports back from their internal discussions on stabil-ity testing of ADAs performed in the regulated bio-analytical environment. Additional Information.

These antibodies are called rabies virus neutralizing antibodies (RVNA).

The highly complex nature of plasma can impact on the physiochemical properties of mAbs. As a result, the serum stability should be appropriately assessed using both in vitro and in vivo methods. For in vitro analysis of antibody serum stability, the antibodies can be incubated in serum from different species for a period of time.

Specimen Type Temperature Time Special Container; Serum: Refrigerated (preferred) 14 days : Frozen : 14 days: Reject Due To. As a new antibody is developed, Cell Signaling Technology (CST) scientists test the antibodys stability and activity following a storage period of more than 7 Anti-immunotherapeutic antibodies are stable in undiluted serum samples stored at -80C for at least 3.5 years and 3-12 freeze-thaw cycles. serum.

of the rst monoclonal antibody (MAb) product-OKT-3 in 1986, more than 23 MAb drug products have entered the market (Tab.

Test Code VEDOZ Vedolizumab Quantitation with Antibodies, Serum Ordering Guidance. Antibody half-lives in CSF ( CSF t ) approximated their serum half-lives ( serum t ).

Antibodies have long been an integral component of both therapeutics and laboratory research (1,2).Starting out with early antisera, applications rapidly expanded with the

15,16,19 Further, maleimidethiol linkages are susceptible to hydrolysis and the retro-Michael reaction which can lead to thioether exchange with free Cys,

Measurement of antinuclear antibodies (ANA) in serum is the most commonly performed screening test for patients suspected of having a systemic autoimmune rheumatic disease Complement Fixation Test: In a reaction between an antigen with its cognate antibody present in serum, the complement disappears from the serum because of binding to the antigen-antibody complex. Albumin and the respective fluorescently labeled antibody chains are denoted.

Ordering Guidance.

Conclusion: Samples were selected to cover the heterogeneity of the polyclonal human immune response, therefore this stability data can be extended to all anti-vaccine and anti-drug antibodies. Technique # 1. can I Test Code HISTO Histoplasma Antibody, Serum Additional Codes. Indicate thyroid status of patient including presence of exophthalmos.

Density:

SARS Coronavirus 2 IgG. Serum antibodies can recognize both pathogens and commensal gut microbiota. Analyte Stability: Primary tube: 3 days at 15 to 25 C. Separated from cells: 7 days at 2 C to 8 C.

Antibody stability in a dry solid state is sensitive to pH [ 21 ], which plays a dominant role in determining the physical stability of the IgG1 in the lyophilized state, with pH 5.0 being the most stable.

Positive (100 IU/mL): IgG antibodies to pertussis toxin (PT) detected. Aliquoting Purified Antibody: The purified antibody (which contains sodium azide) can be safely stored at 4C for 2-3+ months at a time in order to avoid freeze/thaw cycles. stability was assessed by enzyme-linked immunosorbent assay/enzyme immunoassay (ELISA/EIA), indirect immunofluorescence assay. Tg is not

Antiserum. It is the principal iodoprotein of the thyroid gland and constitutes the majority of thyroid mass.

All antibodies tested have been found to be just as active and stable when stored at room temperature as on ice.

In mammals, most proteins circulating in the serum undergo constant uptake by endothelial cells and are routed through the endosomes to the lysosomal compartment for degradation. + Biologicals specifically mAbs active components are typically proteins and/or polypeptides Therefore maintenance of molecular conformation and, hence of biological activity, is dependent on non-covalent as well as covalent forces. Pre-clinical in vitro models have gained scientific interest as they enable one to evaluate the in vivo stability of monoclonal antibodies (mAbs) and ultimately can improve patient safety. The facts indicate that antibody therapeutic development programs must incorporate understanding of the basic biology of the isotype and its stability in serum, which is the intended environment of the therapeutic. Draw blood in a gold-top serum gel tube (s).

Anti-Sec61 Antibody serum, Upstate; find Sigma-Aldrich-07204 MSDS, related peer-reviewed papers, technical documents, similar products & more at Sigma-Aldrich Detect Sec61 using this Anti-Sec61 Antibody validated for use in IP & WB. Population-wide diversity and stability of serum antibody epitope repertoires against human microbiota.

Patient Preparation: For 12 hours before specimen collection, do not take multivitamins or dietary supplements containing biotin (vitamin B7), which is commonly found in hair, skin, and nail supplements and multivitamins.

Clinical Information. Recommended first-line test for detection of /thyrotropin receptor antibodies. > 5 mg/day) for three days prior to specimen collection.

222 mAbs Volume 2 Issue 3 between the HC Table 1 Amino acid sequence of hinge region for different IgG isotypes.

All antibodies are labile to one degree or another by freezing conditions, presumably due to the damage incurred during ice crystal formation.

Avoid high biotin doses (i.e.

Room temperature: 7 days Refrigerated: 14 days Frozen: 30 days.

Patient Preparation.

Thus, laboratories that continue heat-inactivating serum are likely to obtain false-positive results with some EIA kits (6,7).

Specimen Type Temperature Time Special Container; Serum: YEAST BY CF.

Patient Preparation: For 12 hours before specimen collection, Specimen Stability Information. In a therapeutic context, however, the cytotoxic effector function of an antibody is often not desirable and can Antibodies of classes G, D and E are of monomeric type H2L2. 1.30-1.49 IV: Equivocal - Questionable presence of West Nile virus IgG antibody detected.

Clinical Information.

Specimen Stability Information. A set of 19 serum samples was assayed once a month on a plate from same lot stored at 4 C.

Comparison of the InBios and Focus Diagnostics DV IgM EIA. The Application to Stability Studies In vitro stability was conducted by Specimen Stability Information. The approximate volume of blood needed for this test is 1.0 mL of blood (0.5 ml of serum or plasma). 1 EVCit ensures high ADC stability and efficacy in mouse models (figures from our paper with modifications).

Single-domain V H H antibodies to serum albumin with nine amino acid differences have dramatically different thermal stabilities and binding affinities. The persistent presence of IgG and/or IgM cardiolipin (CL) antibodies in moderate or high levels (greater than 40 GPL and/or greater than 40 MPL units) is a laboratory criterion for the diagnosis of antiphospholipid syndrome (APS).

The general acceptance criteria for incurred sample reanalysis for ligand-binding assays were applied, as well as alternative stricter acceptance criteria promoted by various white papers. 2.2 DAR & DOP Drug antibody ratio (DAR) is the number of payloads per antibody High DAR = diminished stability and pharmacokinetic profile Low DAR = reduced potency The BioPlex 2200 Measles IgG assay uses multiplex flow immunoassay technology.

An antibodys stability greatly influences its performance (i.e. Adenovirus Antibody, Serum - Adenoviruses can cause acute respiratory infections and conjunctivitis, as well as infantile diarrhea.

Specimen Stability Information. Abstract. Patient Preparation: For 12 hours before specimen collection do not take multivitamins or dietary supplements containing biotin

Negative in normal individuals; also negative in dermatitis herpetiformis or celiac disease patients adhering to gluten-free diet. (A-F) A Downloaded from https://www.science.org on November 25, 2021 subset of serum and saliva sample pairs (n=71) collected from the same patient within 4 days were analyzed for

Serum.

Specimen Required. This study focused on two Interpretation.

HISTO CF. The total number of IgA molecules in these bodily secretions is greater than the number of IgG molecules in the blood serum. The presence of serum thyroid antibodies usually indicates an autoimmune thyroid disorder, but elevated levels may also be detected in other conditions. -based detection assay for the quantitation of immunoglobulin G serotype-specific antipneumococcal antibodies in human serum. In general, antibodies are known to remain stable in frozen storage over lengthy periods. Specimen

Storage Conditions for Antibodies and Antibody-Enzyme Conjugates Antibody stock solutions (e.g., 1 mg/ml) often may be stored at 4C for days to weeks without significant loss in activity.

Stability Test Results.

The rationale for choosing SST vacutainers over other vacutainer types is that antibody titers are usually higher in serum than in plasma.

A set of 19 serum samples was assayed once a month on a plate from same lot stored at 4 C.

We used a novel approach by stripping serum of endogenous proteins, which interfere with analytical test methods. Reporting Name Histoplasma Ab, S Useful 1 pink-top (EDTA) tube. Specimen Type Temperature Time Special Container; Serum Red: Refrigerated (preferred) 7 days : Thyroglobulin autoantibodies bind thyroglobulin (Tg), a major thyroid-specific protein.

Synonyms Anti-GQ1b, FGQ1B. In RFFIT, the serum (the non-cellular portion of blood) is first diluted fivefold (1 part serum in 4 parts diluent).

Gross hemolysis: Reject:

Thus, stability is a major issue for researchers and manufacturers, especially with the increasing use of antibodies in therapeutics, diagnostics and rapid analytical platforms. Application to Stability Studies. Note: Freeze at -20 C for long term storage. Dear Sir, In May 2021, Sasmono et al.

Heat-inactivation of serum specimens before they are screened by enzyme immunoassay (EIA) for HIV antibody can give false-positive results (6,7). There are numerous publications regarding

The previously found results (1988-2004) and those obtained in 2006 were.

Borderline (40-<100 IU/mL): Recommend follow-up testing in 10 to 14 days if clinically indicated.

2 Persistence of antibodies in the serum of affected individuals.

Fig. Specializing in antibodies and antibody based tools for basic research, assay development and more for over 50 years. Half-life is calculated as the final data to evaluate the in vitro stability of your BsAbs.

Human serum antibodies are stable for At least 4 freeze/thaw cycles At least 6 years at -20C At least 2 weeks at 4 C At least 72 hours at room temperature Freezing on dry ice for 4 hours Conclusion on internal stability studies 17 Antibodies are generally considered to be very stable when stored at or below -20C (1, 2)

Torrance Memorial Laboratories Test Code: 62872572. This test is performed using a multiplex flow immunoassay method and screens for antibodies to a limited number of nuclear antigens. Processing Instructions: 1.

Antibody engineering methods have been required to identify suitable maleimidethiol linkage sites because local structural and chemical environments dictate reactivity and conjugate stability. You searched for: Publication year rev 7978-2022 Remove constraint Publication year rev: 7978-2022 Publication Year 2022 Remove constraint Publication Year: 2022 Subject enzyme-linked Antibody classes Characteristic IgG klor klor klor klor klor g Y structure Light chain Heavy chain IgM IgA IgE IgD m a e d Fig. The method of detecting ACIC uses HD as the detection index, which is sensitive and accurate, with good stability of detection results, and has certain clinical application value. Specimen It does not screen for all antibodies associated with myositis, scleroderma, or autoimmune liver disease. Blood cells, plasma, and serum are required. Positive: Positive for Varicella IgG antibodies, Specimen Stability Information. Clinical Significance: Measuring IgG antibodies to GQ1b ganglioside in serum as an aid in diagnosis of acute and chronic neuropathies.

and stability.

These discussions are an inte

These TRFIA

Measurement of antinuclear antibodies (ANA) in serum is the most commonly performed screening test for patients suspected of having a systemic autoimmune rheumatic disease (SARD), also referred to as connective tissue disease. Thyroglobulin (Tg) is a glycoprotein of molecular weight 660,000. Method Description. Influenza A and B Antibodies, Serum - Influenza Type A and B viruses cause seasonal outbreaks of the flu. Therefore, A1-A1 effectively interferes with two pathological mechanisms of B2GPI/antibody complexes: the binding to anionic phospholipids and ApoER2. For increased stability, glycerol or ethylene glycol may be added to a final concentration of 50% and the antibody stored at -20C.

The titer of IgA-EMA generally correlates with the severity of gluten-sensitive enteropathy.

Thyrotropin-receptor antibody is an autoantibody to the thyroid cell receptor for thyroid-stimulating hormone. Additional Information. One lot was tested over a 12 month period and a second lot was tested for 5 months of storage. Thus, the stool samples analyzed in these experiments may be less stable on a per-individual level than serum antibody repertoires. By measuring functional serum Ig-epitope repertoires against 244,000 peptides in 997 individuals, we detected a multitude of private and public antibody responses against antigens of gut microbiota. This linker is cleaved by

The stabilizer protein also serves to minimize the antibody loss due to binding to the vessel wall.

In a combination of monoclonal antibodies, separate antibodies are used together. A Sypro orange is not evaluated some antibodies can also Negative (positives reported as band present) Day(s) Performed. The principle is to determine the concentration of active BsAb molecules after being incubated with human serum at 37 C for a certain time. Background: To generate exhaustive data on the stability of human anti-vaccine or anti-drug antibodies, we designed a GLP study using anti-vaccine antibodies (AVA) samples collected from over 100 different subjects.

IgM: IgM antibodies to Borrelia burgdorferi may be detectable within 1 to 2 weeks following the tick bite; they usually peak during the third to sixth week after disease onset, and Note: 1.

Stability of anti-immunotherapeutic antibodies in frozen human serum samples Frozen-state storage stability of a monoclonal antibody: aggregation is impacted by freezing rate and solute distribution

Specimen Type Temperature Time Special Container; Serum: Refrigerated (preferred) 21 days : Frozen : Stable

Test Code TGABI Thyroglobulin Antibody, Serum Serum.

The reconstituted antibody can be stored for several weeks at 2-8C or for up to 1-2 years at -20C. (AB) Fluorescent (top) and Coomassie stained (bottom) SDS-PAGE gels are shown for LC-V205C and Fc-S396C conjugates. dicate that antibody therapeutic development programs must incorporate understanding of the basic biology of the isotype and its stability in serum, which is the intended environment of the therapeutic. Previous studies on antibody stability in serum or plasma at 4C are very scarce and old and mostly related to whole blood cells units, where anticytomegalovirus IgG, IgA and

Negative (<40 IU/mL): No IgG antibodies to pertussis toxin (PT) detected. antibody stability, typically in serum. (A-F) Binned ratio-converted ELISA reads We examined the stability of antibody levels over the first three

Specimen Required.

Home .

Stable for 1 year at -20C from date of receipt.

A speckled-top serum gel tube (s) or a plain, red-top tube (s) is Only 4% to 7% of patients with type 1 diabetes are autoantibody negative, fewer than 10% have only 1 marker, and around 70% have 3 or 4 markers. You searched for: Publication year rev 7978-2022 Remove constraint Publication year rev: 7978-2022 Publication Year 2022 Remove constraint Publication Year: 2022 Subject enzyme-linked immunosorbent assay Remove constraint Subject: enzyme-linked immunosorbent assay Subject blood serum Remove constraint Subject: blood serum Subject antibodies Remove constraint

particularly sensitive to environmental factors such as temperature changes, oxidation, light, ionic content, and shear. In Stability assay: The positive reference of the National Reference Panel for IgM and IgG antibodies to COVID-19 was mixed at a ratio of 1:1 for stability evaluation.

Table 1.

Volume : 55% of the total blood is plasma.

In vitro stability was conducted by spiking T-DM1 at a concentration of 50 g/mL in buffer (PBS, pH 7.4 with 0.5% BSA) and in mouse serum. One MPL unit is 1 microgram of IgM antibody. Allow serum sample to clot for 30 minutes.

a chemical structure of EVCit linker. Repeat testing in 10-14 days may be helpful. Refrigerated: 7 Days.

the Palsson* Department of Chemical Engineering, University Frozen: 3 Months. Results: Anti-immunotherapeutic antibodies are stable in undiluted serum samples stored at -80C for at least 3.5 years and 312 freezethaw cycles.

Test ID: HCVL Hepatitis C Virus Antibody Confirmation, Serum Useful For. Tg plays a crucial role in thyroid hormone synthesis, storage, and release. 1 published their interesting work, which reported on widescale use of antibody seroprevalence to examine the history of Zika virus (ZIKV) transmission in Indonesia.

Test Code SEBV Epstein-Barr Virus (EBV) Antibody Profile, Serum Additional Codes. (1) ANA occur in patients with various autoimmune diseases, both systemic and organ specific, but they are particularly common in

As a new antibody is developed, Cell Signaling Technology (CST) scientists test the antibodys stability and activity following a storage period of more than 7 days at -20C, at room temperature and at 37C. Test Code ABTIR Antibody Titer, Blood and Serum Shipping Instructions.

If quantitative results are needed, please fax Immunochemistry at 616-267-2771 or call 616-267-2770. For very short periods of time, serum may be stored at 4C.

Assay stability . Serologic tests for autoantibodies, including smooth muscle antibodies (SMA), should not be relied upon exclusively to determine the etiology or prognosis of patients with liver disease. The amount of total antibody and ADC in rat serum samples and in samples prepared for the in vitro serum stability study was evaluated using a quantitative sandwich

Serum. All IgG, IgM and IgA from various species are detected using recombinant antigen The method of detecting ACIC uses HD as the detection index, which is sensitive and accurate, with good stability of detection results, and has certain clinical application value. Note: Performance has not been established with cord blood, neonatal specimen, cadaver specimen, heat-inactivated specimen, or body fluid other than serum or plasma such as saliva, urine, amniotic fluid, or pleural fluid.

Confirming the presence of hepatitis C virus (HCV)-specific IgG antibodies in serum specimens that are reactive by HCV antibody screening tests.

Sample Volume.

This sandwich ELISA allows the detection of antibodies against HEV in serum samples. Specimen must arrive within 72 hours of collection.

Stability Study Services Antibody Modification. Confirming the presence of hepatitis C virus (HCV)-specific IgG antibodies in serum specimens that are 2.

Adenovirus Antibody, Serum.

Torrance Memorial Laboratories Test Code: 62871930. Storage at -80C isnt necessary.

The 20 mM histidine buffer samples (pH 6.0) were incubated in a chamber under accelerated stability conditions, i.e., 40 C and 75% relative humidity. St. Louis Encephalitis Antibody, IgM by IFA, Serum.

(A-F) A Downloaded from https://www.science.org on November 25, 2021 subset of serum and saliva sample pairs (n=71) collected from the same patient within 4 days were analyzed for correlations in levels of anti-spike and anti-RBD IgG, IgA and IgM antibodies.

The finding of IgA-endomysial antibodies (EMA) is highly specific for dermatitis herpetiformis or celiac disease. Test Code VZPG Varicella-Zoster Antibody, IgG, Serum Additional Codes.

The serum is less in volume comparatively. Specically, conjugates that

Reference values apply to all ages. Commonly used methods for stability test, such as

Stability: 7 days

In our study, we compared the physical stability of 8 different monoclonal antibodies (mAbs) in phosphate-buffered saline (PBS) and human serum. ELISA and

Methodology Adenovirus Antibody, Serum: 3400012: 3400012: Adenovirus Antibody, Serum: 5041-9: No: Need Help? 15.0-39.9 MPL or GPL (weakly positive) 40.0-79.9 MPL or GPL (positive) 80.0 MPL or GPL (strongly positive) MPL refers to IgM Phospholipid Units.

If the antibody concentration is low, stabilizer proteins such as BSA can be added to the antibody solution. Knowing the stability of an antibody is essential in many cases. The major hurdle of using mouse models to predict antibody stability in the serum lies in the way immunoglobulin proteins are processed by the organism. Primary antibody is polyclonal calreticulin and secondary antibody is Alexa Flour. Equivocal: Suggest repeat testing in 2-4 weeks or longer if clinically indicated.

Elevated results are obtained with this streptavidin-biotin method for samples with biotin concentrations > 41 nmol/L.

Specimen Stability Information.

Must be spun/separated within: 2 Hours. Mumps Virus Antibody Testing (Serum) Mumps Virus IgG: Mumps is an acute, usually self-limited systemic illness characterized by parotidites, high fever and fatigue.

In this study, we used centrifugal ultraltration to strip human and bovine serum of macromolecules >3 kDa. 1 mL. Positive: IgG antibody to

AChR blocking antibody testing is no longer offered individually as it offers no added-value to the diagnosis and management of MG. Specimen Stability Information. Parameter to other antibody stability serum protocol as a gradient of sorbitol and resources on the protein that for the time. CPT Description. Briefly, serum samples are mixed and incubated at 37 degrees C with sample diluent and dyed beads coated with measles antigen.

Reported as Immune or Not Immune.

For testing such patients, order HBCSN / Hepatitis B Total Antibodies Screen, Serum. Antibody serum and CSF concentrationtime curves converged until they became parallel after CSF T max was reached.

Interpretation. The serum also contains antibodies, to cross-react with the recipient antigen.