T and B cell activation

T and B cell activation

• 1.
  T- cell andB- cell activation BY- YASHI JAIN 1
• 2.
  B-cell activation  Dependingon the nature of the antigen, B-cell activation proceeds by two different routes, one dependent upon TH cells, the other not.  B-cells are APC which are activated either by antigen or by isotype switching  T-helper cells recognize antigen bound class II MHC on B-cell, interaction CD40 and CD40L provides signal  B7 –CD28 interaction provides costimulation to the T-helper cells  After these interaction B-cell releases various cytokines  Activation of B-cell leads to proliferation and differentiation into plasma cells 2
• 3.
  Two Types ofSignals Drive B Cells into and Through the Cell Cycle: Signal 1 and Signal 2 Transduction of Activating Signals Involves Ig α/Ig-β Heterodimers 3B-cell activation and proliferation
• 4.
  Role of Cytokines Interaction of cytokines with B-cells generate signals which is required for proliferation and class switching during the differentiation of B-cells into plasma cells  Binding of the proliferation cytokines which are released by activated by T helper cells provides the progression signal which is needed for proliferation of activated b cells.  Class switching is the response to thymus-dependent antigens also requires the CD40/CD40L interaction 4
• 5.
  T-cell activation  TCRrecognize peptide bound MHC, when it interacts there is transfer of signal which cause release of interlukins hence leads to proliferation, makes clonal expantion and differentiates into memory and effector T-cell  Activation of T-cell occurs only when it recognizes antigen bound peptide with MHC molecule in any of the APCs  Two signals which are important for activation of T-cells are: interaction between MHC peptide and TCR, interaction between CD 28 of T-cell and B7 of APC 5
• 6.
  Diagrammatic representation ofT-cell activation 6
• 7.
  Difference between T-cellsand B-cells 7
• 8.
  Superantigens are classof antigens which cause non- specific activation of T-cells resulting in polyclonal T-cell activation and release of cytokines 8 Superantigens induce T-cell activation by binding the TCR and MHC
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