Development of adaptive immune cells

Development of adaptive immune cells

1. Lymphocyte receptors

   • BCR = B cell receptors
     • Have same structure as an antibody
       • I.e. complementary to antigen
   • TCR = T cell receptors
     • Are linear
       • Must have antigens presented to it by other cells
       • Alpha and beta chain

2. Variation in lymphocytes

   • Allows greater range of protection
   • VDJ segments
     • Somatic recombination
     • Combinatorial diversity
   • Different combinations of heavy and light chains
   • Junctional diversity
   • Secondary diversity
     • Arises from somatic hypermutation = random mutations
       • Alters affinity of receptor for its antigen
         • Clonal selection = Only B cells with a high affinity for antigen bind and receive survival signals
           • Affinity maturation = Progressively makes the 2o response more effective
     • Occurs in variable chain of cloned B-cells, produced after activation

3. Tolerance

   • Central
     • T cell selection in the thymus
     • Positive selection
       • T cells that bind weakly with MHC undergo apoptosis
         • Basically: T cells that bind strong enough to self or non-self peptides on MHC do not undergo apoptosis
     • Negative selection
       • T cells that bind strongly with presented self antigens undergo apoptosis
         • Basically: T cells that have a high affinity for self peptides on self MHC undergo apoptosis
   • Peripheral
     • When regulatory T cells suppress other immune cells
       • Important because not all self antigens are present in the thymus.
     • Cells becoming anergic if they don't receive correct signals
   • Destroys T cells that would respond to antigens on self cells

4. MHC

   • Protein coded for by HLA gene
   • Class 1 = innate
   • Class 2 = adaptive
   • Function = to present antigens to adaptive immune system