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Questions tagged [antigen]

An antigen is a substance which causes the the body to produce a reaction of the adaptive immune system. Contact of the immune system to antigens results in the production of highly specific (antigen specific) antibodies.

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Do antibodies binding to the same epitope have similar electrophoretic mobility?

Serum protein electrophoresis is a commonly used blood test in medicine. It is often used for detection of paraproteins in the gamma-globulin region. If there is a narrow band with sharp borders ...
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Other than the major histocompatibility complexes, what is the difference between professional and non-professional antigen presenting cells?

Can both professional and nonprofessional APCs activate helper T-cells? Or is that only macrophages and B-cells? Do cytotoxic T-cells only make non-professional APCs go into apoptosis?
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Can In Vivo Gene Therapy Cause allorecognition/Rejection?

Organ rejection from organ transplants is least common when donors and receivers are genetically related; As I understand it, this is because the antigens on the surface of the cells of the donated ...
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What can lymphocyte-produced antibodies do that 'innate' opsonins can't?

I have a conceptual misunderstanding relating to immunology which I'd be grateful if anyone could help me clear up. My A Level textbook says that at the start of an immune response, opsonins bind to ...
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What exactly is bound by the control line on COVID19 antigen tests?

Clearly the test line binds some component of the coronavirus, I believe most commonly the nucleocapsid protein (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8049777/). However, despite extensive ...
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CDRs and antigen-binding sites [duplicate]

Are complementarity determining regions (CDRs) not the same thing as antigen-binding sites? If not, what is the difference? An old exam question states: "Clarify how CDRs are related to the ...
user71502's user avatar
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What causes Erythroblastosis fetalis?

So this is what I understood about the disease by researching about it When a Rh-ve mother has a Rh+ve baby in her womb, The placenta prevents mixing of fetal and maternal blood preventing antigen ...
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Can typed-switched B cells recognize the tertiary structure of antigens?

As T helper cells are responsible for isotype switching but Th cells are MHC class 2 restricted and MHC only presents denatured peptides (up to 30 residues, no folding), does that imply that only IgM ...
Rand's user avatar
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Why can't SARS-CoV2 antigen lateral flow tests be used for testing animals?

Real use case: Two male neutered Felis catus individuals live in a household where up to three humans live of which all were infected with SARS-CoV2 at the same time, proven by antigen and PCR tests. ...
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Antigen transfer from baby to mother

When considering immunity in babies, the main mechanism that supports their undeveloped immune system is the transfer of antibodies from mother to baby via breastfeeding. Case #1: both baby and mother ...
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What is the significance of an adjuvant to traffic vaccine antigen directly to draining lymph nodes without diffusing into the systemic circulation?

I found the following sentence in the this paper- Safety and immunogenicity of an inactivated SARS-CoV-2 vaccine, BBV152: a double-blind, randomised, phase 1 trial An imidazoquinoline molecule, which ...
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Why are O-antigens and H-antigens on (certain) bacteria called O and H?

Somehow, despite extensive searching, I cannot find an answer.... Does O stand for oxygen and H signify hydrogen?
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Boost of Janssen COVID-19 Vaccine increasing Immune Response to Vector

I have been looking for published, or even pre-print, data that evaluates the serological response to a boost of the Janssen COVID-19 Vaccine against the adenoviral vector Ad26 rather than the ...
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Detecting multiple compounds on a lateral flow immunoassay – is this a case of monoclonal vs polyclonal antibodies?

I am working on developing lateral flow immunoassays for drugs of abuse and needed some advice on detecting multiple drug compounds in one immunoassay. As an example, an existing LFIA on the market ...
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Why do T cells have MHC II receptors?

I have seen the answer to this question which says that T cells do not express MHC II proteins which would make sense. However, my textbook "The immune system" by Peter Parham disagrees. It ...
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Are antibodies removed before blood transfusion

I am an O blood group person meaning, I can donate my blood to all as I don't have any Antigen A and B. But my body does contain antibodies A and B right? If they were along with the donor blood, ...
Adil Mohammed's user avatar
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Sensitivity vs. Limit of Detection of rapid antigen tests

I'm comparing a bunch of SARS-CoV2 rapid antigen tests: Source Columns 4 and 6 list the values for sensitivity and limit of detection (LOD). How come that a test with a several times lower limit of ...
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What is a function-triggering antibody?

I am reading a journal paper on the effect of a neural cell adhesion molecule on neuronal development and in the abstract of this paper I have come across the following: The autophosphorylation and ...
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Can any molecule become a hapten?

Hapten are small-molecules, that can only become immunogenic when conjugated with a carrier protein. I was wondering if all small-molecules can become haptens (eg. by synthetic conjugation). Given ...
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With the 5$ covid19 test - an antigen test - , would trials (most likely) be independent?

Actual question What would typically cause antigen tests to give a false positive or false negative and would these causes be typically independent (if we run the test twice it won't automatically ...
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Easy and cheap antigen/antibody couple

For an application I need to find a cheap antigen and cheap correspondent antibody. The antigen can be literally any molecule that is cheap and potentially easy to produce and with a correspondent ...
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1 answer
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Could there be a pathogen which does not activate an immune response?

In order for the immune system to be stimulated to produce antibodies, there must be a surface protein of the invading pathogen which binds to a receptor on B cell surface somewhat loosely. We need ...
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1 answer
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Are all antibodies against a common antigen identical? [duplicate]

I understand that when some antigen (e.g., virus, bacteria, etc.) is recognized in the body, antibodies specific to this antigen are produced that, in turn, bind to the antigen and effectively ...
user38694's user avatar
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Reasons why this protein is not suitable as an immunogen?

In a paper entitled "Progress and Prospects on Vaccine Development against SARS-CoV-2", the authors write the following in section 2.5: "Compared with S, N, and M protein, E protein is not suitable ...
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Is it possible for virus infected cells to continue to present a self-antigen on the MHC1?

Forgive my ignorance, as I'm new to immunology, however it seems like there would be some amount of positive selective pressure for viruses to develop the ability to continue to present the host's ...
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1 answer
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How are antibodies specific for a disease detected in the blood if everybody produces a different antibody for the same antigen?

To break the title down into parts: There exist serology tests that detect the amount of an antibody (Ab) against a specific pathogen/antigen. Every human produces their own Ab for a specific ...
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How does the immune system find the DNA code for antibodies

There are millions of possible antigens. To respond to each antigen, the immune system must quickly produce an antibody by modifying the DNA of a B cell. I have no idea how this process works, but ...
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1 answer
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Are hormones antigenic?

I have been asked whether hormones are antigenic. I would have to think that the answer is no because they are used as various drugs such as FSH in infertility treatments without the need of ...
Shabbs15's user avatar
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1 answer
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What happens to the molecules of the pathogens after phagocytosis?

For example, what happens when a bacterium gets digested by a macrophage? I suppose that the macrophage produces the presented antigen from leftovers from the digested bacterial particles. What ...
Aun's user avatar
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2 answers
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Are tumor-associated antigens unique to cancerous cells?

Are tumor-associated antigens found only on the membrane of cancerous cells or just over-expressed on the membrane of carcinogenic cells? In other words, are these antigens also found on healthy ...
ahmed ashraf's user avatar
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1 answer
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What is meant by 'fixing' of an antigen presenting cell?

Can someone please explain what does 'fixing' of an antigen presenting cell mean?
MONIS MUSHTAQUE's user avatar
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1 answer
72 views

Can MHC class I be used for presenting peptides of extracellular origin by non-professional APCs?

Wikipedia says that: "The antigens presented by MHC class II are derived from extracellular proteins (not cytosolic as in MHC class I)." So does this mean that MHC class I cannot be used for ...
mingoo426's user avatar
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1 answer
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Choosing viruses for influenza vaccine

When scientists choose viruses for the influenza vaccine based on biological and clinical data, what indicates that a certain strain will circulate and likely be dominant in a certain season? Does a ...
FIREREED's user avatar
1 vote
1 answer
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How does one predict how large of an effect on antigenic drift a substitution in the amino acid sequence of a surface protein of influenza has?

I know that some amino acid substitutions are more effective in causing antigenic drift than other substitutions based on their location in the 3d structure of the HA protein (proximity to the ...
FIREREED's user avatar
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1 answer
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Can multiple antibodies bind the same antigen?

Given the size difference between small molecule antigens and antibodies is it ever possible for multiple antibodies to bind to the same antigen if they recognize different domains on that antigen? ...
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1 answer
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Why are vaccines a successful treatment of allergy?

As I understand the answer to Allergic rhinitis vaccine, the vaccine facilitates immune response against the antigen. Given that allergy is an overreaction of the immune system against harmless ...
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CD4 Proteins & Antigen presenting cells

If Helper T-Cells express CD4+ proteins on their surface to bind to MHC Class ll proteins on antigen presenting cells, why do antigen presenting cells also have CD4+ Proteins?
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1 answer
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Vaccines against bacterial endotoxins

Today in class, there was a discussion going on about what part of pathogens(which can act as an antigen) can be used to make vaccines. There was this point where our teacher said that bacterial ...
anamika Singh's user avatar
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1 answer
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Will a sandwich assay work with a GST 26 antibody/protein?

I have a GST 26 kda antibody, and want to use it in a sandwich lateral flow assay. Are there enough epitope regions for both antibodies to bind to the protein?
Shreyas Kallingal's user avatar
4 votes
1 answer
177 views

Autoimmunity - negative selection of T-cells - APC

Through negative selection of T-cell in the thymus T-cells lose the possibility to react to antigens which are "body own" -> self antigens. Though there are more than just this negative selection for ...
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4 votes
1 answer
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How does adjuvant enhance the immunogenicity of antigen? [closed]

My question is, How does adjuvant enhance immunogenicity of antigen? I just want to know deeply about it , Any suggestions will be helpful!
Ubdus Samad's user avatar
5 votes
2 answers
442 views

How do scientists discover a new antigen and its epitope?

I've found some database on the internet that list all discovered antigens and their epitopes. So how do scientists discover a new antigen? Do they try to inject them into the body to see if it ...
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1 answer
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Detect which antigen binds to IgE

Assume that a patient has chronic hives (itchy) on the skin. I understand that he has an antigen, which binds to IgE and eventually triggers histamine release, causing an allergic reaction. So is ...
joe's user avatar
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0 answers
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Are antibodies and hepatitis viruses of similar adaptability?

Antibodies and Hepatitis viruses both have hypervariable regions. Is one more adaptable than the other? Precisely how adaptable are they? I have read that antibodies can be trained to bind to ...
Dale's user avatar
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Do allergens have structural similarities to pathogens?

The conventional popular explanation of allergies is that the immune system confuses allergens with pathogens and reacts to them as such. Is there any merit to this explanation? If so, I would ...
Joshua Meyers's user avatar
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O-Group names of Salmonella serotypes?

What liposaccharides are represented by the O-group designations of Salmonalla serovars in the Kauffman-White classification scheme? I mean to ask, how do the numbers in a Sal serovar (1, 9, & 12 ...
AlexanderF's user avatar
6 votes
2 answers
1k views

How is a T lymphocyte specific to an antigen but not specific to an epitope?

In my immunology notes, it states that B lymphocytes (and other APCs) capture and present antigens to T lymphocytes that is specific for an antigen, but that the T cells do not necessarily recognise ...
Elizabeth's user avatar
1 vote
1 answer
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Why does the blood not clump and result in death?

In this question's accepted answer, it is said that the blood type will slowly change to that of the donor's. When the blood in the person is about 50% his own and 50% that of the donor's. i.e, 50% A ...
Shirin Riana's user avatar
5 votes
1 answer
2k views

Minimum size for a peptide/protein to be immunogenic in human?

What is the minimum size for an (injected) peptide/protein to cause immunogenic response in human? A reference is very helpful, as well. Thanks in advance
biofan's user avatar
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2 answers
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What are blood group determinants? [closed]

I am trying to understand if they are the same as the blood antigens. The books I have tried to read say something about them being the antigens on the surface of the red blood cell.
Twalumba Munongo's user avatar