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Hypersenstivrt 4

pharmacogonosy ppt

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Hypersenstivrt 4

  1. 1. DEFINITION “ excessive and undesirable reaction produced by normal immune system.”
  2. 2. Hypersensitivity Type IV General concept Delayed type hypersensitivity ( takes 2 or 3 days to develop). No antigen antibody mediated response. Cell mediated response.
  3. 3. Cells involved in Hypersensitivity Type IV T Lymphocytes : are further divided into two types. Helper T Cells (CD4) Cytotoxic T Cells (CD8)
  4. 4. Antigen Recognition  T cell fail to recognize antigen in the absence of Antigen presentation.  T cell receptor is restricted to recognize antigenic peptide only when bound to the appropriate molecule major histo compatibility complex (MHC).  This is called MHC restriction.
  5. 5. Two Categories of Antigen Are processed and presented to T cell by two different mechanism. Exogenous Antigen Endogenous Antigen
  6. 6. Exogenous Antigen  Present MH class II.  Are taken by the Antigen presenting cells (Dendritic cells ; Macrophages).
  7. 7. Antigen Presenting Cells:  Engulf the antigen by endocytosis.  Endosome fuses with the Lysosome.  So antigen is degraded into fragments.  Display on cell surface by combining with MHCII  Here they may be presented to CD4 helper T cells.  CD4 helper T cells then become activated.
  8. 8. Function of Activated CD4 (Helper T cells)  Responsible for regulatory functions.  Produce interleukin  Interleukin 2 activates CD4 and CD8 also called as T cell growth factor.  Interleukin 4 and 5 are activator of B cells.  Gamma Interferon activates macrophages; NK cells; neutrophils.
  9. 9. Function of Activated CD4 (Helper T cells)
  10. 10. Endogenous Antigen Present MHC1 class. Antigen present within the cell e.g, viral protein in any infected cell are;  Degraded into peptide fragment.  Peptide fragment form a complex with MHC I.  Displayed at the cell surface.  Here they may recognize by CD8 ( Cytotoxic Cell).
  11. 11. Function of Activated CD8 cell Perforins: formation of channels through the membrane. Pore formation. Cell content is lost. Cell dies.
  12. 12. CD8 ( Cytotoxic T Cells) Granzymes: Proteases Degrade protein in cell membrane loss of cell content Cell dies
  13. 13. Activation of CD8 (Cytotoxic T Cells)
  14. 14. Function of Activated CD8 (Cytoxic T Cells)