Immunology IV Flashcards
What is the cellular component of the adaptive immune system?
Cytotoxic T cells directly attack antigen-bearing cells.
Lymphocytes develop receptors for every pathogen that we might experience by the process of […]
Somatic hypermutation
Somatic hypermutation occurs in […]
B cells and T cells
What are the two enzymes involved in somatic hypermutation?
- The Recombination activating genes (RAGs)
- Terminal Deoxynucleotidyl Transferase (TdT)
Describe the function of RAGs in somatic hypermutation.
The Recombination activating genes (RAGs) will splice out some of the V, D, and J genes on the DNA, leading to a reduced pool of possible genetic combinations for receptors.
Describe the function of TdT in somatic hypermutation.
The Terminal Deoxynucleotidyl Transferase (TdT) will add single nucleotides to the ends of these gene blocks, which will cause frame shifts and further change the combinations of receptors. It will ultimately splice out one V, one D, and one J for the variable region.
What is the end product of somatic hypermutation?
The end result will be mRNA with one variable region made up of a V, D, and J gene, and one constant region, made up of a C gene.
The category of antibody (IgE, IgG, etc.) is determined by its […] region.
Constant
When you get an infection, the first antibodies to be produced in the primary response are […]. because […]. They are followed by […] in [smaller/equal/greater] quantites.
IgMs, because they are good for activating complement. igGs, equal.
The secondary response to an infection involves the production of which antibody type(s) and in what quantities?
It results in the rapid production of a lot of IgGs and a small quantity of IgMs.
The first time you have an infection, the first antibody to respond is […]. Why?
IgMs, because they are good at activating complement due to their large size.
The second time you get an infection, the first antibody to respond is […]. Why?
Although IgGs and IgMs both respond, IgGs dominate because they are effective in moving throughout the body.
When you get an infection in mucosal tissue, the major antibody to be produced will be […]
IgAs
How does the body know not to attack its own cells?
It recognizes the major histocompatibility complex (MHC) of the body, which is unique (except in identical twins). During development, any lymphocytes that might target our own body are removed.
The process of getting rid of lymphocytes that might attack our own body cells is called […], which has the end goal of […]. When does it occur?
Clonal deletion/clonal inactivation, immune tolerance. It occurs during fetal and early postnatal life.
Describe the steps by which the development of T cell tolerance occurs
- T cells that don’t recognize MHC Class II are negatively selected, as this makes them useless.
- T cells that recognize MHC Class I-self peptide complexes are negatively selected to prevent against self-attack.
[…]% of T cells never leave the thymus. Why?
95%. This is because after negatively selecting for T cells that either can’t recognize MHC II or can recognize MHC I-self, there are not many left that are of use to the body.
Why do we get an amplified immune response upon second exposure to disease?
Because of the memory cells produced by B and T cells. This allows for faster and greater production of the correct antibodies to fight off the infection.
What is the role of T cells in the adaptive immune system? How do they get activated?
They are used in cell-mediated immunity to eliminate specific antigens. They only get activated once they see the foreign antigens that they target.
What is the difference between an exogenous antigen and an endogenous antigen?
An exogenous antigen leads to the antigen-presenting cell that we’ve seen thus far. It is when something from the outside is producing an immune response, such as a toxin from bacteria. An endogenous antigen is when the body cells get infected and themselves produce the immunogen.
How does the response of the immune system differ for endogenous antigens as opposed to exogenous antigens?
In the case of exogenous antigens, MHC II molecules are synthesized by APCs and bound to the fragments of antigen, and presented by antigen-presenting cells. On the other hand, for endogenous antigens, MHC I molecules are synthesized by the infected cell and bound to fragments of the antigens, which are then presented to T cells in a similar way.
Explain the process by which cytotoxic T cells get activated.
In a secondary lymphatic organ, a dendritic cell will still bring in a pathogen and present it with the MHC-II molecule. This leads to the activation of the helper T cell, which then activates the cytotoxic T cell by releasing cytokines (no direct contact).
Explain how cytotoxic T cells deal with infected body cells once they’ve been activated.
The cytotoxic T cell will find a match for its receptor by travelling out of the secondary lymphatic organ. Its receptors have to match infected cells via a recognition event. The infected cell must be presenting the antigen along with the MHC I protein for the recognition event to be successful. The cytotoxic T cell will then release perforins and granzymes to kill the cell.
Explain the process by which infected body cells present antigens with MHC-I.
When the cell has been taken over and is producing viral proteins, these proteins will be digested into fragments. At the same time, MHC-I molecules will be produced, as they normally would be, and they get packaged together and displayed on the cell via exocytosis.
