TB Testing of Cattle Flashcards
1
Q
Delayed Type Hypersensitivity (DTH)
A
- CMI immune response that occurs after prior sensitization
- peaks at around 72 hours after infection
- Th1 CD4+ cells make cytokines that attract macrophages and macrophages get activated by interferon-gamma
- downregulated by Th2 CD4+ cytokines
2
Q
Caudal Fold Test (CFT)
A
- Test for CMI (Mycobacterium Ag specific Th1 CD4 T cells)
- inject mycobacterium
-> examine injection site at 72 hours for inflammation - if inflammation is present, then mycobacterium has infected/or is infecting the cow and memory Th1-CD4 T cells are present
MECHANISM - PPD presented by APC to memory Th1 CD4 T cells specific for that antigen, proliferation/cytokine production, MO migrate to site and call in neutrophils causing inflammation
- false positive due to prior exposure to diff Mycobacterium
- in vivo
3
Q
Comparative Cervical Test
A
- if CFT is positive, federal vets test specifically for M bovis and M avium
4
Q
Interferon Gamma Release Assay (IGRA)
A
- test for CMI
- use whole blood sample from patient PPD added
- test measure the amount of IFN-gamma made from the Th-1 CD4 T cells
- control is run
- only need one visit, takes 24 hours
- no false positives
- in vitro
