PSIO 431 Assignment for Type III IV Immunopathology 1 One shot serum sickness requires only a very small dose of foreign antigen True or False False There needs to be an excess amount of antigen present in order for this Type III immunological response to happen When an anti serum is given the body can mistake the anti serum as antigens that are harmful to the body This will cause the body to make an immune response to these antigens and create antibodies through B cells This then causes complexes to form between the anti serum and the antibodies leading to activation of complement and inflammation 2 Name two organs that are innocent bystanders in Type III immunopathology and give an example of an antigen whose antigen antibody complexes might be preferentially targeted to each of these organs The kidneys and the lungs are two examples of innocent bystanders in Type III immunopathology Because the kidneys are the main location for filtration when a Type III immunological response takes place these complexes that are formed can get stuck in areas of filtration in the glomerulus This would lead to a decrease in filtration at the level of the kidneys which can cause adverse effects on the entire body This can happen for example after being exposed to streptococcus and can be seen in acute post streptococcal glomerulonephritis In hypersensitivity pneumonitis aka Farmer s Lung the complexes form in the lungs Exposure to thermophilic Actinomycetes make their way into the lungs through inhalation and then the body sees this as a bad foreign antigen and makes IgG antibodies against that foreign antigen This leads to complement complexes which get stuck in the lungs causing inflammation and makes it difficult for a person to breathe 3 Why doesn t a TB skin test elicit a Type III response instead of a Type IV response hint think about where M tuberculosis live A TB skin test is done by injecting the antigens intradermally so that they don t penetrate the dermal part of the skin layer which could infect a person This means that it wouldn t be seen by B cells and then it wouldn t create an antibody against it which otherwise would lead to the formation of an immune complex Instead the delayed hypersensitivity response takes about 48 72 hours to reach its peak and show the results of the persons TB skin test 4 Name 2 major differences between Type III and Type IV immunopathology Type III forms immune complexes and requires B cells in order to create antibodies that come together with antigen in order to form the complexes that get stuck and cause inflammation Also Type III is considered to be the least intuitive As for Type IV it is T cell mediated and requires no B cells It is delayed hypersensitivity The underlying problem with Type IV is disordered immune regulation which means that there is an issue in creating the correct immunological response 5 Why is it important to remove or impair T cells from transplant donor tissues if the MHC s of the donor and recipient are not ideally compatible If a donor and the recipient of the transplant are not histocompatible it will lead to the graft rejecting the host or vise versa The T cells will recognize the hosts HLA as foreign and therefore the graft will reject the host this is known as graft vs host disease Graft vs host disease may happen acutely where the host is immunosuppressed due to Treg cells attempting to make the graft work or it may happen chronically where activated T cells do not stop producing cytokines This excess release of cytokines can lead to compromised regulation of the hosts immunological functions If the T cells are not removed or impaired this can lead to an immunosuppressed host 6 In terms of cells lymphokines secreted locations and timing describe what happens when a person is exposed to poison ivy for the first time and what happens when they are exposed a second time The first phase is initiation or immunization In this phase a person is first exposed to the antigen The antigen can become associated with the hosts MHC on the dendritic cell where it goes to draining lymph nodes and presents MHC antigen to Th0 precursors in order to decide which T cell should be made either Th1 or Th17 which are both pro inflammatory These cells then go on to divide and increase in number with memory cells being made but without a reaction because the antigen on the skin will have been washed or worn off before anything can happen The second phase is the elicitation stage During this stage is where the response occurs due to memory T cells that are present and this can initiate a reaction faster This dictates that a reaction will happen when exposed to poison ivy for the second time This will lead to inflammation and visible signs of a reaction within 6 12 hours and begin to really peak within 24 48 hours after the second exposure Citations Cohen Z Fall 2015 Type III Immunopathology In Immunology Cohen Z Fall 2015 Type IV Immunopathology In Immunology