Immunopathology Type 4, Immune Regulation

Question 1

Define Type IV immunopathology

Answer 1

T-cell mediated immunology

Question 2

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.

Answer 2

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

Question 3

Explain why a person usually has no observed symptoms when first exposed to poison ivy.

Answer 3

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

Question 4

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.

Answer 4

With regards to Cytotoxic T Lymphocytes, sometimes an epitope can directly associate with MHC without being processed, which will activate T cell proliferation

Question 5

Discuss in principle how T cell immunity could be measured in the laboratory.

Answer 5

You can measure IFN-y levels with TB gold tests, or just the mantoux test by measuring the growth of the induration

Question 6

Explain why TB skin tests can be administered repeatedly to the same subject

Answer 6

The amount of immunogenic material is so small, it can’t ellicit memory cells

Question 7

Differentiate between a first-set and second-set graft rejection

Answer 7

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

Question 8

Define hyperacute rejection and indicate the mechanism

Answer 8

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

Question 9

Discuss the three requirements for graft-versus-host disease to occur.

Answer 9

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

Question 10

Discuss how autoimmunity can result from environmental exposure to tissues that cross-react with human organs.

Answer 10

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

Question 11

Define the graft-versus-leukemia phenomenon.

Answer 11

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.

Question 12

Abacavir

Answer 12

Reverse transcriptase inhibitor for HIV

Some people got systemic delayed hypersensitivity because they are HLA-b57, where they’re able to present abacavir to their immune system