Immune system

Nota:

• -work within minutes after a pathogen invasion

1. Characteristics
   1. less specificity

      Nota:

      • general, attack pathogens
   2. Fast responses

      Nota:

      • not require time to develop
   3. Required receptors

      Nota:

      • recognize pathogen-associated molecular patterns(PAMP)
2. Mechanisms/Actions

   Nota:

   • 1. phylogenetically order 2. exist before or react immediately after contact with pathogen(no memory) 3.react predominantly to infectious agents 4.First line defense 5.stimulate and shape adaptive immunity
   1. Phagocytosis(major)
   2. Antigen-recognition
      1. Responsible by NK cells

         Nota:

         • 1. no antigen receptors 2. have surface receptors that inhibit killing function: -Kill inhibitory receptor(KIR):recognize abnormal levels of MHC class I(normal : NK cells do not kill it ; lower amounts(usually the indicator of infected cells/tumor cells): will be killed) 
         1. The importsnce

            Nota:

            • 1. Viral can interfere with the expression of MHC-avoid the killing by CD8+ T  cells: NK cells are important for catching these infected cells
3. Cells and functions
   1. Mast cells

      Nota:

      • 1. inflammation
   2. Monocytes/Macrophages

      Nota:

      • 1 Phagocytosis 2.inflammation 3.T-cell activation 4.Tissue repair
   3. Neutrophils

      Nota:

      • 1. Phagocytosis 2. Inflammation
   4. Neutral Killer cells

      Nota:

      • 1.Killing of infected or tumor cells(through detect the amount of MHC I) 2.Activation of Macrophages(by IFN-y)
   5. Eosinophils

      Nota:

      • 1. Defense against parasite
   6. Dendritic cells

      Nota:

      • 1. Phagocytosis 2. Activation of Naive T-cells

Nota:

• -take times for the responses to a specific pathogens with memory -Highly specific -it work when the innate immunity cannot control and eliminate the pathogen. -with the ability to form "memory' of the pathogen -Quickly response: the organism is infected with the same pathogen

1. Cells
   1. B and T lymphocytes

      Nota:

      • 1. Have surface proteins(antigen receptors): recognize only one antigen 2. T cells: responsible for one small peptide 3. B cell: responsible for more than just a small peptide once the antigen binds the receptor of B cell/Tcell, they are activated and triggers an immune response.
2. Mechanism/reaction
   1. Antigen recognition
      1. The formation of recptors
         1. combine conserved areas of receptor

            Nota:

            • with variable gene segments 1. recombining DNA 2. DNA mutation
      2. Differences between T and B cell receptors

         Nota:

         • Structure: BCR:Divalent TCR: monovalent
         1. Target antigen

            Nota:

            • B cells : antigen in native form T cells :only recognize antigen fragments with epitope size
         2. Need assistant

            Nota:

            • B cells : does not need help from other cells to recognize antigen T cells: only recognize peptides in the presence of MHC (a surface protein)-antigen has to go through antigen processing
         3. restriction*

            Nota:

            • T cells : MHC restricted and hiscompatible to be activated
            1. MHC

               Nota:

               • -Highly variable proteins:that allow the immune system to recognize self from non-self -also know as HLA(human leukocyte antigen)(CLASS II):type individuals for BM and organs transplates -inherited one set of Class I(A,B,C) and Class II(HLA-DR,DP,DQ) from each parent(expressed equally).
               1. Types
                  1. MHC class I

                     Nota:

                     • 1.expressed on all nucleated cells 2. responsible for graft rejection 3. MHC I must be expressed/by target cells to be killed by an antigen-specific CD8+ T cells
                  2. MHC class II

                     Nota:

                     • 1. expressed by immune cells(macrophages,dendritic cells, T cells and B cells)

Nota:

• -derived from Myeloid stem cell

1. Eosinophil
2. Basophil
3. Neutrophil

   Nota:

   • 1.contains granules 2. CD66 membrane marker protein

1. Lymphocytes

   Nota:

   • -T cells -B cells -NK cells
   1. T cells
   2. B cells
   3. Nature-killer cells

      Nota:

      • 1. used in experiment:to test the ability of lymphocytes to kill specific target cells 
2. Monocytes(Macrophage)

   Nota:

   • 1. Macrophage=Large,eating      -Lysosomes      -CD14 membrane marker protein 2.Function:-ingest and eliminate infectious agent-regulate other immune cells(both innate/adaptive)
3. Plasma cell

   Nota:

   • -differentiated from B Lymphocyte
4. Dendritic cell

   Nota:

   • 1.reside in tissue in an immature form: -mature when an infection/injury occurs 2.The role of mature DC: -travel to the lymphoid organs with antigen on their surface(antigen-presenting cells) -can present the antigen on the surface of T-cells

1. Epithelia
   1. Chemical barrier
   2. Intraepithelial lymphocytes
   3. Normal bacterial flora
   4. Physical barrier

Nota:

• -allow the immune system to react more quickly and effectively to a stimulus that has encountered before.

Nota:

• respond to the pathogen that is at hand