A231 Team 3 L06 Page 1 by https://padlet.com/190028901/rd2xe17ifvnsqe6m Made with a wish on a star en-us 2020-06-03 02:07:16 UTC 2020-06-03 09:52:51 UTC hello@padlet.com 190028901 https://padlet.com/190028901/rd2xe17ifvnsqe6m/wish/608010708 Positive selection --> T cell that reacts to only foreign peptides 
Negative selection --> removal of auto-reactive by apoptosis

Both selection process occurs in the bone marrow and lymph nodes (as there are more lymph nodes than thymus. thymus is the center for maturation).]]> 2020-06-03 02:29:29 UTC https://padlet.com/190028901/rd2xe17ifvnsqe6m/wish/608010708 190028901 https://padlet.com/190028901/rd2xe17ifvnsqe6m/wish/608023209 In bone marrow --> Naive T Progenitor cells that has CD4 and CD8 receptors

Clonal deletion: T cells that bind to self-peptide --> undergo apoptosis

In thymus, self antigens are presented to developing T cell from bone marrow --> when T cell bind to MHC-2 -->  differentiate to be CD4
When T cell bind to MHCB-1 --> differentiate to MHC-2 (Receptor Editing)

If T cell fail to bind either MHC-1 or MHC-2 --> undergo apoptosis]]> 2020-06-03 02:45:09 UTC https://padlet.com/190028901/rd2xe17ifvnsqe6m/wish/608023209 The Different Types of Transplant jes_leenminecrafter https://padlet.com/190028901/rd2xe17ifvnsqe6m/wish/608034969 1) Autograft (transplant from one part of the same individual to another part of the same individual)
2) Isograft (transplant from a living organism to a genetically identical individual of the same species)
3) Allograft (transplant from a living organism to another genetically different individual of the same species)
4) Xenograft (transplant from a living organism of one species to another living organism from another species)]]> 2020-06-03 03:00:58 UTC https://padlet.com/190028901/rd2xe17ifvnsqe6m/wish/608034969 190171132 https://padlet.com/190028901/rd2xe17ifvnsqe6m/wish/608203528 Positive and Negative Selection only takes place in the Central Tolerance

It takes place in lymph nodes when after puberty when the thymus shrinks. ]]> 2020-06-03 06:10:32 UTC https://padlet.com/190028901/rd2xe17ifvnsqe6m/wish/608203528 Peripheral Tolerance Mechanisms 190171132 https://padlet.com/190028901/rd2xe17ifvnsqe6m/wish/608204965 There other mechanisms such as
  • Immune Deviation
  • Immune Privilege
  • Immunosuppressive Cytokines
  • Regulatory T cells

These controls quality, intensity and duration of the T cells 
]]> 2020-06-03 06:11:45 UTC https://padlet.com/190028901/rd2xe17ifvnsqe6m/wish/608204965 190171132 https://padlet.com/190028901/rd2xe17ifvnsqe6m/wish/608207234 Affinity Maturation takes place after Positive and Negative Selection and occurs in the Peripheral Tolerance]]> 2020-06-03 06:13:30 UTC https://padlet.com/190028901/rd2xe17ifvnsqe6m/wish/608207234 190028901 https://padlet.com/190028901/rd2xe17ifvnsqe6m/wish/608277829 Class 1 and 2 MHC can be a form of Human leukocyte antigen (HLA). This is important when organ transplantation. Every individual have unique MHC.]]> 2020-06-03 07:06:43 UTC https://padlet.com/190028901/rd2xe17ifvnsqe6m/wish/608277829 190028901 https://padlet.com/190028901/rd2xe17ifvnsqe6m/wish/608287577 In acute rejection,
T cells go through primary response and secondary response. Organs gets rejected due to different HLA and blood type. Memory B cells are created, affinity maturation of B cells. If you try to transplant the same organ again, it will definitely be rejected because the immune system has recognized this 'foreign' invader. Acute rejection will become accelerated. (?)]]> 2020-06-03 07:13:01 UTC https://padlet.com/190028901/rd2xe17ifvnsqe6m/wish/608287577 190028901 https://padlet.com/190028901/rd2xe17ifvnsqe6m/wish/608294684 In a organ transplantation, organ may carry different MHC and carry its own self-peptide that is different than the host self-peptide.

B cell recognizes self-peptide as a foreigner and produce antibodies for it.]]> 2020-06-03 07:17:38 UTC https://padlet.com/190028901/rd2xe17ifvnsqe6m/wish/608294684 Immune Privileged Sites jes_leenminecrafter https://padlet.com/190028901/rd2xe17ifvnsqe6m/wish/608547970 - Locations such as the brain, eyes, testis and placenta have a higher degree of tolerance to the antigens and are not used in negative selections. 
3 Mechanisms:
1) Sequestered antigens hidden between anatomical barriers to prevent T cells from reaching the location
2) Presence of Treg which supresses the immune response
3) High FasL expression which kills effector T-cells through Fas. (e.g. sperm cells have FasL which binds to the Cytotoxic Tcells and induce apoptosis on the Tcells which prevents the killing of sperm cells)]]> 2020-06-03 09:47:47 UTC https://padlet.com/190028901/rd2xe17ifvnsqe6m/wish/608547970