Hot answers tagged

13

At one of my previous companies that raised antibodies to proteins and post-translational modifications, we found that 6-8 amino acids was generally the smallest peptide length required for an epitope. Anything much smaller than that won't induce the cross-linking or conformational changes required for signal transduction and an allergic response. As WYSIWYG ...


12

Small molecules do not have antigenic properties but they can elicit immune response by binding to a "carrier" protein. The small molecule is called a Hapten. An epitope forms at the protein-hapten binding interface. Nickel acts like a hapten and elicits immune response by binding to proteins like transferrin, albumin etc. Other metals also cause ...


6

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 different purposes. In order to discover a natural antigen, which is recognised by an antibody normally produced by the immune system, one would first have ...


6

Although transmissible cancer has been found in some species, such as Tasmanian Devils and clams, it is quite rare in most species. Certain viral and bacterial agents that cause cancer, however, can be transmitted. One example is HPV, which can cause cervical cancer


5

The group tries to predict possible epitope sequences for the generation of antibodies. This includes also non-linear epitopes where not all amino acids of the epitope are line up behind each other, but come in close contact due to a 3D-structure. To train their algorithm, they use data, where the boundaries of the epitopes and the non-epitopes are known and ...


5

The blood type of people is determined by proteins which are anchored into the surface of the red blood cells. Cells can either express the A, B, A and B or no marker, resulting in the blood groups A, B, AB and 0. People which have a certain blood type (for example A) have antibodies against the other blood type (in this case B). This will lead to the ...


4

For the generation of Fab-fragments antibodies, (possibly genetically modified) which can be made in large quantities by cells or animals, are used. Antibodies as a whole are not synthesized. The Fab fragment is obtained from antibodies using the enzyme papain, which cleaves the antibody over the disulfide bonds in the hinge region. This results in two Fab ...


4

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 binding groove in MHC-I actually limits the size of peptides it can load to 8-10 amino acids, 9 being the most common. This is because "pockets" at either end of ...


4

Actually there are such particles. It is estimated that about 20% of the hemoglobin (HGB hereafter) is in HGB vesicles (HbV hereafter) formed by RBCs. So sure, it is possible to use small particles instead of RBCs, but these vesicles have major and minor antigens on their surface. According to some of the articles they cause other complications too by blood ...


4

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 immunogen which is a type of antigen that causes your immune system to produce antibodies. But an antigen does not necessarily have to be an immunogen. ...


4

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 that sells antibodies for research. To help understand the quote, you'll need to know that the portion of an antigen that an antibody binds is called an epitope. ...


3

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 its references. 1) Aluminum salts (aluminum phosphate or hydroxide) Studies suggest alum salts work by causing the formation of an antigen depot at the ...


3

It's common for the human immune system to create antibodies against many proteins, even some human proteins. Hemophiliacs who receive regular doses of clotting factor proteins often develop neutralizing antibodies against the clotting factor proteins, even though they are a human protein1. Therefore it's not surprising that antibodies would be developed ...


3

They actually can produce antibodies against the clotting factor (as @Xylo pointed out, many patients do produce the clotting factor that's being replaced, just in insufficient quantity, which lowers a lot the risk of an immune response). The antibodies against the clotting factor are called inhibitors. See here for more info.


3

You are absolutely right in that there will be immune reaction against proteins that are not naturally present in the body. However, hemophilia is not caused by complete lack of protein. It is due to loss of function of the clotting factors due to mutations. The proteins are still present, but they do not have the ability to bind and/or activation of their ...


3

If you have an antibody that is directed against, for example, a bacterial surface protein, then by mixing the bacterial cells with the antibody at a suitable stoichiometry you could observe clumping of the cells as the antibody molecules essentially cross link the cells together. This would be an example of using an agglutination (clumping) assay with a ...


2

Let's clarify the terms. An antigen is a molecule that can be associated with a particular substance (virus, pollen, dander.) When an immunoglobulin or antibody recognizes an antigen it binds to a specific epitope. An antibody recognizes an epitope using its paratope. Some antigens have multiple epitopes; this means that different antibodies can ...


2

Self-antigens are not recognized by the body. This is due to self-antigens being presented to the immune system of the body during the embryological development. Any immune cell which recognize the pattern are destroyed during the intrauterine period, preventing the emergence of Auto-immunity in the Life-time. Self-antigens become important in the ...


2

There can be many responses. They are important for alloimmunity (so by transfusion, transplantation, etc...), for recognizing pathogens, cancer, virus, etc... By T cell activation, the regulator T cells recognize these antigens as self, and prevent the autoimmune reaction. I guess they were thinking on MHC1 and MHC2. MHC1 shows the inside of the cells, so ...


2

This is a concept of the immune system called "Immune tolerance". Basically it makes sure, that you cannot make antibodies against yourself (which would obviously be bad). New antibodies are "tested" against the body and if there is an autoreactivity, the corresponding B-cells go into apoptosis. If this self-protection does not work, this leads to autoimmune ...


2

FAbs are genetically engineered and not organically synthesized as such. This PNAS article nicely describes the construction of a phage (virus) library to generate a large amount of different FAbs and screen for FAbs with the wanted epitope (antigen) affinity: http://www.pnas.org/content/95/11/6157.short


2

No. When a different blood type is introduced in the body, the host immune system recognizes the foreign blood as non-self and attacks it. The transfused blood becomes useless, and the potentially massive immune reaction can cause shock, which itself can be fatal. More details in the book Blood Groups and Red Cell Antigens, which can be found at the NCBI ...


2

As mentioned in the comment, all antibodies have constant regions and variable regions. The variable regions are the binding sites on the ends of the two arms, and the constant regions are the rest of the molecule. When humans are injected with murine antibodies, the immune system recognises and sets up an immune response to them, through generation of HAMA. ...


2

What attracts leukocytes and antibodies to pathogens in the first place? They just bump into them. If secreted antibody is already present in the blood then complement system can be activated. What attracts CD4+ cells to professional antigen-presenting cells (APC)? APC release chemokines. All that is known is that this is a CC-type chemokine and ...


2

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 pointing "regions" of the antigen that an antibody will bind to. Since the B cell makes the antibody you can think of these regions as where the B cell will bind ...


2

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. Some of its broken proteins, which are antigens are presented on the MHC II of this particular APC. The B cells also do something similar but they identify ...


2

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 clumps (or clots) as a result of an antibody interacting with a surface cell antigen. They can form tiny clumps, however, that are not life threatening, but simply ...


2

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 their effects on structure is at best oversimplified. Rather than spend many paragraphs reviewing the complex patterns involved, I'd suggest you start by ...


2

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 question is a little confusing. You're asking about cross-presentation, which is the process by which extracellular antigen can be presented to CD8 T cells on ...


2

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, and outside of the cell: inside the cell (intracellular), at the cellular membrane and exposed to the extracellular environment, or even secreted. Depending on ...


Only top voted, non community-wiki answers of a minimum length are eligible