Flashcards in Immunopathology Type 4, Immune Regulation Deck (12)
Define Type IV immunopathology
T-cell mediated immunology
Describe the cellular and molecular events following intradermal injection of tuberculin antigen into a person who has cell-mediated immunity to it. Justify calling the process ‘delayed hypersensitivity’. Characterize the cells that would be seen in a 48-hour biopsy of the site with regard to whether T cells or macrophages predominate.
So assuming that the pt has been exposed to TB, they will have an expanded number of Th1 cells with memory to TB, the mantoux test will be positive, INF-y will be released, and macrophages will attract.
You would see a lot of macrophages
Explain why a person usually has no observed symptoms when first exposed to poison ivy.
The first, you get immunized against the poison ivy resin, but there isn't enough antigenic exposure to actually illicit an immune response, because the first time is just the "initiation". Ellicitation is when you get a reaction
Discuss how a chemical or small peptide might not need to be processed through an antigen presenting cell to be presented by that cell to T cells.
With regards to Cytotoxic T Lymphocytes, sometimes an epitope can directly associate with MHC without being processed, which will activate T cell proliferation
Discuss in principle how T cell immunity could be measured in the laboratory.
You can measure IFN-y levels with TB gold tests, or just the mantoux test by measuring the growth of the induration
Explain why TB skin tests can be administered repeatedly to the same subject
The amount of immunogenic material is so small, it can't ellicit memory cells
Differentiate between a first-set and second-set graft rejection
1st- 10% of mhc will be recognized as foreign, so eventually you're gonna get rejected. 10-20 days
2nd- your cells will remember the graft, so it will reject faster, 5-10 days
Define hyperacute rejection and indicate the mechanism
If you keep trying to graft without immunosuppresion, they will reject before even healing in. Stays white and bloodless due to preexisting antibody
Also can happen with ABO antigenicity
Discuss the three requirements for graft-versus-host disease to occur.
1.) Graft must have immunocompetant T cells
2.) Must be at least one antigen in the host which the graft T cells can recognize
3.) Host should probably be relatively immunoincompetant
Discuss how autoimmunity can result from environmental exposure to tissues that cross-react with human organs.
MS! Masically there is a lot of autogenic things in our body that aren't immunogenic. For example our brain is protected by a blood brain barrier, but when we're exposed to an outside source that APCs can pick up that epitope and present it to T-cells not deleted because AIRE does not upregulate brain antigens
Define the graft-versus-leukemia phenomenon.
Many studies have shown that leukemia patients who receive stored, pre-treatment
bone marrow from themselves, or T-depleted allogeneic marrow, have the
fewest GvH symptoms; but they also have a higher rate of leukemia relapse compared to those who get allogeneic marrow that still has some T cells.