Adaptive immune system Flashcards
(21 cards)
How long does the adaptive immune system take to respond?
Can take anywhere from days to weeks, has variable recognition elements, is highly specific and provides an immunological memory to improve the next response. Is the 2nd line of defence
What are antigens made of?
Most of them are proteins, but some are carbs, lipids or nucleic acids
What are antigens?
Molecular determinants that can be recognised by antibodies, B and T-cell receptors, this induces an immune response
What are immunogens?
Molecular determinants that induce or elicit an innate and/or adaptive response such as antigens. Antigens are immunogens but not all immunogens are antigens
Where are B cells produced?
In the bone marrow, they are then matured in the spleen
Where are T cells produced?
In the bone marrow, they are then matured in the thymus
What happens when B cells become activated?
They differentiate into effector cells (plasma cells). Their main function becomes the secretion of antibodies. After differentiating they lose their receptors, stop dividing and most die within 1-2 weeks, but some migrate to the bone marrow as long term memory cells
What are thymocytes?
T cells undergoing maturation in the thymus
What initiates the adaptive immune system?
The interaction between antigen presenting cells (APC) and naive T cells
How are dendritic cells activated and what do they do?
They are typically activated at the site of inflammation/infection via pattern recognition receptors. They process and present peptides from the pathogen in complex with MHC I and II and travel to the lymph node and/or spleen.
What cells recognise MHC I and II complexes?
The rule of 8, CD4+ lymphocytes are activated upon recognition of antigens presented on MHC II molecules, while CD8+ lymphocytes are activated upon recognition of antigens presented on MHC I molecules
What is severe combined immunodeficiency?
A disorder where the child possesses few T cells, NK cells, and absent B. Missing immune response, because of this causes recurrent viral and fungal infections. If untreated the child will die before the age of two
What is IgA?
Neutralising antibody secreted by epithelial cells, they protect mucosal surfaces and are present in breast milk and saliva, they are resistant to proteases
What is IgD’s function?
It is the main BCR together with IgM on mature B cells where they control B cell activation and supression
What can IgG mediate?
Antibody-dependent cell-mediated cytotoxicity (ADCC) by NK cells
What does IgE do?
Causes degranulation of eosinophils in defence against parasite and causes degranulation of mast cells and basophils in response to an allergic reaction
What is positive and negative selection? (long answer)
Positive selection occurs in the thymus cortex and determines whether the T cell can recognise MHC I or II, if it can it will be given survival signals and depending on which MHC it recognises determines which CD cell it will become. The T cell will then move into the thymus medulla where it will undergo negative selection to determine if it responds too strongly to peptides, if it does it can trigger autoimmune diseases so it will be told to undergo apoptosis. If the T cell passes both of these checks it will move out fo the thymus into the lymph node
What are the differences between B and T cells?
Maturation sites, B cells secrete antibodies that can recognise a variety of organic and inorganic molecules, whereas T cells recognise protein antigens only. B cells can recognise antigens by themselves, whereas T cells require the antigen to be presented to them
When is the adaptive immune response launched?
When the innate immune system is overwhelmed
What do T helper cells and cytotoxic T cells do?
cytotoxic T cells (Tc cells) fight against intracellular infection via cell-mediated cytotoxicity, while T helper cells (Th cells) activate Tc cells, B cells and phagocytes
What are professional APC?
APC that present antigens on their surface using both MHC I and II.
