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Flashcards by Afronewtzz, updated more than 1 year ago
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Created by Afronewtzz
almost 9 years ago
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| Question | Answer |
| What cells are antibodies secreted by? | Mature B cells. |
| What is an antibody? | A protein that is able to interact with antigens and with cells of the immune sytem. |
| What is meant by the 'lock and key reaction' of antibodies and their corresponding antigen? | When the antigen recognition region of the antibody is specific for the antigen in order for binding to take place. |
| How do antibodies interact with cells of the immune system? | Via their Fc portion. All immune cells have an Fc receptor which binds this Fc portion. |
| How does an antibody send an immune response? | If an antibody has an antigen bound to its antigen recognition site and then its Fc portion binds to an Fc receptor on the surface of an immune cell - this triggers an immune response. |
| What 3 direct roles do antibodies have in protecting the body against invaders beside alerting other cells of potential danger? | - Neutralisation - Opsonisation - Complement fixing |
| What is meant by neutralisation (antibodies)? | When antibodies work to neutralise infective agents and their secreted toxic products. They can do this in 2 ways: - Antibodies bind to the surface of the invader - antibodies are able to bind particular molecules that the invader uses to adhere to host cells - this prevents host cell invasion and damage to the host cell. - Antibodies can also neutralise secreted bacterial toxins which may otherwise damage host cells. |
| Give 2 examples of toxins secreted by bacteria which can be neutralised by antibodies. | Teteanus toxin Cholera toxin |
| What is meant by Opsonisation (antibodies)? | Opsonisation is the process of coating bacteria with antibodies. - One example could be when all kinds of proteins are exposed on the bacterial surface are recognised by specific antibodies and so opsonisation enhances the clearance of bacteria by immune cells through a process of phagocytosis/ ingestion. Once ingested, the phagocytic cell will kill the bacteria. - OR virus-infected cells recognised by exposing virus antigens > NK cells kill infected cell via antibody-dependent cell cyctotoxicity/ ADCC. NK cell holds Fc receptors for Fc portions of antibodies which are bound to virus-infected cell. |
| What is meant by Complement fixation (antibodies)? | - Antibody: Antigen complexes are able to activate complement via the classical pathway. - Complement comprises a set of proteins which are activated. - Antibody: Antigen complexes formed on the surface of cells leads to the activation of complement components and the fixation of complement component C3b to the pathogen surface.. - This leads to the formation of the membrane attack complex and the destruction of pathogens. |
| When does our body produce antibodies? | - Encounters infection - During pregnancy - Organ transplantation |
| What is meant by Seriodiagnosis? Give 3 assays of seriodiagnosis. | A diagnosis based on the reaction of blood serum. - Haemagglutination assay - Cell viability test as part of HLA matching - Enzyme-linked immunosorbent Assay (ELISA) |
| Give 3 ways in which the ELISA test is used. | - Prenatal diagnosis of the foetal rhesus type. - Determination of tissue transplant compatibility. - Detection of specific infections (e.g. viral and bacterial). |
| What is the difference between a Direct ELISA assay and an Indirect ELISA assay? | - Direct ELISA = Uses monoclonal antibodies to detect the presence of a particular antigen in a sample. - Indirect ELISA = Used to determine the presence of a specific antibody e.g. antibodies to HIV in a specimen such as serum. |
| Describe how a DIRECT ELISA assay works. | (Used to measure the amount of antigen) - Antigen is usually bound to the well of an ELISA plate. - After the enzyme-labelled primary antibody binds to the antigen, it can be detected through an enzyme reaction. |
| Describe how an INDIRECT ELISA assay works. | (Used to determine the presence of a specific antibody) - The primary antibody will be specific for the antigen of interest but it is not linked to an enzyme. - A secondary antibody specific for the primary antibody will be conjugated to an enzyme and it is therefore possible to quantify how much primary antibody has bound to the antigen of interest. |
| Describe a variation of Indirect ELISA assay such as a 'capture' ELISA or 'sandwich' ELISA. | This allows complex antigen samples (i.e. serum) to be assayed for the presence of a specific antigen e.g. HIV virus. It will consist of a primary antibody > antigen > primary antibody > enzyme linked secondary antibody. The primary antibody initially lining the well will detect the antigen's presence. |
| What is haemolytic disease of the newborn? | A severe form of anaemia in a fetus/ newborn infant by incompatibility with the mother's blood type - typically when the mother is Rhesus negative and produces antibodies that attack Rhesus positive fetal blood through the placenta. |
| What is the name of the antigen found on RBCs which can be held responsible for haemolytic disease of the newborn? | Rhesus/ RhD |
| What happens if an RhD positive child is born to an RhD negative mother? | During birth, foetal cells can cross into the maternal circulation, during this time, these cells can sensitise the mother and lead to the production of anti-RhD antibodies by the mother. The anti-RhD antibodies are able to cross the placenta during a second pregnancy. If the second foetus is also RhD positive, the anti-RhD antibodies enter the foetal circulation to destroy the foetal erythrocytes. |
| What is involved in a Haemagglutination assay when testing for the presence of RhD antibodies? | Assaying the foetal blood with the maternal serum. If the maternal serum contains antibodies to the red cells of the foetal blood, haemagglutinin occurs. If there are no antibodies in the serum, no haemagglutination will occur. |
| Describe how blood typing works. | - Carbohydrate antigens are on the surface of RBCs. - Antibodies bind to the surface of the RBCs and cause the cells to agglutinate. - We can test if individuals (from their blood sample) express antibodies to these surface antigens and work out the individual's blood type. - An individual with a specific blood type, will not develop antibodies to those antigens. - i.e. people with blood group A do not have antibodies to A, but they will have antibodies to B. - i.e. people with blood group B do not have antibodies to B, but they will have antibodies to A. - i.e. people with blood group AB do not have antibodies to A, B, AB or O. - i.e. people with blood group 0 do not have antibodies to O, but they do have antibodies to A, B and AB. - Sooo... blood group A individuals can give to A, and can receive from A and O. - Blood group B individuals can give to B, and can receive from B and O. - Blood group AB can give to AB and can receive from A, B, AB and O (UNIVERSAL RECIPIENT) -Blood group O can receive from only O, but can give to O, A, B and AB (UNIVERSAL DONOR). |
| What is a cell viability test? | A routine basic procedure to investigate the number of live and dead cells in any cell suspension or cell culture preparation. |
| What stain does a cell viability test use? | Trypan blue - cells that appear blue are dead cells with damaged plasma membranes whilst those that appear white or colourless are live cells with intact plasma membranes. |
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