25
votes
Accepted
What exactly is bound by the control line on COVID19 antigen tests?
According to biotrend (SARS-CoV-2 (Covid-19): Rapid Antigen Test for Diagnosis), the control line has an immobilised Goat anti-chicken antibody. There, a chicken-IgY gets stuck which was carried from ...
- 1,769
10
votes
Accepted
Why are O-antigens and H-antigens on (certain) bacteria called O and H?
The "H" and "O" identifiers first appeared in German-language publications around 1920 to describe different forms of disease-causing bacilli. Thankfully, Arkwright and Goyle ...
- 8,256
6
votes
Accepted
How do scientists discover a new antigen and its epitope?
Okay, you have a few questions building on top of each other (rephrased the questions for clarity):
How do scientists discover a new antigen?
There are multiple ways to this, which are applied for ...
- 4,391
6
votes
Accepted
Why can't SARS-CoV2 antigen lateral flow tests be used for testing animals?
I had a look around the literature, and it seems that the tests are slightly less sensitive for some of the variants of concern on non-human saliva samples than they are for human1, but in general can ...
- 11.2k
4
votes
Can multiple antibodies bind the same antigen?
Not only is it possible for multiple antibodies to bind a single antigen, when that happens, it's more likely to trigger a full immune response.
Here's a description of the concept from a company ...
- 8,751
4
votes
How do scientists discover a new antigen and its epitope?
I would like to just add to Nicolai answer.
What is an antigen ?
First, and Nicolai said this, but I just want to make it clear, an antigen is anything that antibodies bind. That is distinct from and ...
- 681
4
votes
Accepted
Minimum size for a peptide/protein to be immunogenic in human?
There's a few limiting factors including how proteins are presented that constrains the actual size needed to get peptide presentation. These depend largely on the MHC molecules (HLA in humans). The ...
- 8,101
4
votes
Sensitivity vs. Limit of Detection of rapid antigen tests
Not necessarily. Sensitivity and specificity are decision criterion-based measures. They are not actually separable from another, they are a consequence of choosing a threshold at which to say "...
- 44k
4
votes
What is the significance of an adjuvant to traffic vaccine antigen directly to draining lymph nodes without diffusing into the systemic circulation?
This paper, Controlling timing and location in vaccines, explains the concept in detail. The TL:DR version is that immune response is affected by the amount of antigen that reaches lymphatic tissue, ...
- 24.7k
3
votes
Why do T cells have MHC II receptors?
That's the description in my book which has the same image.
The book is: Janeway's Immunology (9th Edition)
Article discussing MHC Class II expression in humans:
https://doi.org/10.4049/jimmunol.168.2....
- 815
3
votes
Could there be a pathogen which does not activate an immune response?
"I think, though am not at all sure, that pathogens need to invade cells to be dangerous."
True in the case of viruses and some bacteria.
Hiding within the cells of the host is the ...
3
votes
Accepted
What is a function-triggering antibody?
The term "function-triggering antibodies" is not standard, these are more widely known as cross-linking antibodies. As you may know, an antibody has multiple "arms", with the ...
- 15.2k
3
votes
Accepted
How are antibodies specific for a disease detected in the blood if everybody produces a different antibody for the same antigen?
Specific antibodies are typically detected using ELISA.
The way you make a test for an antibody to a particular pathogen is not by using secondary antibodies to the specific part of the target ...
- 44k
3
votes
Accepted
How does adjuvant enhance the immunogenicity of antigen?
This is a quick answer to a very broad question since the mechanisms of adjuvants are very different. I'll try to summarize just a few. For a deeper understanding please start reading this paper and ...
- 3,098
3
votes
How is a T lymphocyte specific to an antigen but not specific to an epitope?
Perhaps it would simplify for you to think of a model system? Let's take HIV because it's simple. The antigen in this case is a protein called ENV and it looks like this.
All of those arrows are ...
- 681
3
votes
How is a T lymphocyte specific to an antigen but not specific to an epitope?
For this answer lets restrict ourselves to T dependent MHC II mediated responses.
So, an APC like a macrophage or a dendritic cell, takes in a pathogen by phagocytosis and degrades it inside the cell....
- 3,667
2
votes
Accepted
Why does the blood not clump and result in death?
Some people do die from graft vs host disease after bone marrow transplants involving ABO incompatibility, but not usually from blood clots.
Foreign red blood cells don't usually form significant ...
- 24.7k
2
votes
Accepted
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?
Your understanding of influenza antigenic drift is, unfortunately, hypersimplified and mostly wrong. In particular, your notion that some mutations are more important for antigenic drift because of ...
- 14.2k
2
votes
Can MHC class I be used for presenting peptides of extracellular origin by non-professional APCs?
when non-professional APCs that can undergo phagocytosis (Eosinophil, neutrophil, dendritic cell) engulf bacteria
Dendritic cells and probably neutrophils are professional APC, so this part of the ...
- 14.2k
2
votes
Are tumor-associated antigens unique to cancerous cells?
Carcinogenic tumor associated antigens correspond to any peptide chain (antigen) which triggers an immune response from the host. This means that they can be found anywhere inside, at the membrane, ...
- 620
2
votes
Are hormones antigenic?
Hormones have antigens. Usually they are antigens our immune systems recognize as self.
Pretty much any big biological molecule will have antigens. FSH is no exception. The binding of FSH to anti-...
- 2,964
2
votes
Accepted
Is it possible for virus infected cells to continue to present a self-antigen on the MHC1?
Self antigen is presented throughout viral infections. You seem to think that cytotoxic T lymphocytes respond to absence of self. That’s backward. CTL respond to their specific peptide target no ...
- 14.2k
2
votes
Accepted
Detecting multiple compounds on a lateral flow immunoassay – is this a case of monoclonal vs polyclonal antibodies?
Background: I worked for a number of years as a product scientist for a fairly well-known antibody company, designing and producing polyclonal and monoclonal antibodies from several species.
Of your ...
- 15.2k
2
votes
Accepted
CDRs and antigen-binding sites
Each antigen binding site (also known as paratope) is made up of six complementarity-determining regions (CDRs) - three from each of the light and heavy chains.
- 142
1
vote
Why do T cells have MHC II receptors?
Unfortunately the most recent review specialized on this topic (I found) dates back to 2004, and it's pretty confusingly written, IMHO. The general gist of it appears to be that T cells can act as APC ...
- 3,052
1
vote
Easy and cheap antigen/antibody couple
A good choice is the IgG/anti-IgG pair for cheap, easy to demonstrate/work with system. E.g. Goat-IgG coupled with donkey anti-goat IgG. Just about any antibody supplier will have these.
These type ...
- 49
1
vote
Accepted
What happens to the molecules of the pathogens after phagocytosis?
The ingestion of a bacterium by a macrophage involves phagosome lysosome fusion, which you can read about in Abbas Basic Immunology, Ch 2. As you suspected, in addition to bacterial killing and ...
- 8,751
1
vote
Accepted
Are all antibodies against a common antigen identical?
Alright, there are two major questions:
(a) Are all the antibodies that are produced against a specific antigen necessarily identical?
Not in most cases. Antigens can either be monovalent or ...
- 294
1
vote
Reasons why this protein is not suitable as an immunogen?
Firstly, for better immunogenicity, we should select short peptide of approximately 20 amino acids. Longer peptide will definitely increase the immunogenicity, but that also increase the possibility ...
- 1,307
1
vote
Reasons why this protein is not suitable as an immunogen?
The article implies E proteins are quite different between the previous known strains - so a vaccine targeted against E protein may only affect a limited range of strains.
But when I do a BLAST ...
- 2,883
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