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Haematopoiesis (Tests (Diagnostic test: to confirm, Prognostic test: to…

- - - - Commitment of hematopoietic progenitor cells to T cell lineage in THYMUS
        
        TCR receptor
        
        Beta chain in chromosome 7
        
        Contains V D J plus 2 constant gene
        
        Alpha chain in chromosome 14
        
        contains V and J plus single constant gene
        
        V, J, D segment randomly selected by recombinase enzyme (RAG) to create a functional exon via splicing, transcribed mRNA expressed and combined to constant segment
        
        Produces cells with both CD4 and CD8
        
        1 more item...
        
        MHC molecule
        
        CD4
        
        Formed by 4 domains (D1 to D2)
        
        D2 linked to D3 via C2 domain
        
        Binding to co-receptor mainly D1 to Beta 2
        
        CD8
        
        Formed by alpha and beta chains
        
        Binding to co receptor mainly both to alpha 1 and alpha 2
  - - - Formation of Light chain V region containing V,J fragment
        
        Light chain C region encoded in a separate exon joined to V region, forms complete Light chain gene
      - Formation of heavy chain V region containing VJD fragment
        
        C-region exon combined with V domain complete Heavy chain
      - :tornado: Mechanism of somatic recombination :tornado:
        
        Binding of RAG-1 and RAG-2 to recombination signal sequence upstream and downstream of V and J fragment
        
        RAG cleaves RSS to yield a DNA hairpin loop
        
        RAG cleave sharpen loop to form Palindromic P-nucleotides
        
        Terminal Deoxytidyl Nucleotransferase TdT Add single N-nucleotide to the joint, forming single strand
        
        2 strands join back, only those that are complementary will join, the rest is excised by exonuclease
        
        Holes in the DNA are filled and ligated to form a coding joint by DNA synthase and ligase
        
        Give rise to Junctional diversity + Combinatorial diversity :red_flag:
        
        Combinatorial: Fusing random DNA together
        
        Junctional: random nucleotides adding between the fragments
    - - Pro-B: committed to the lineage
        
        Pre-B: Finished recombination , presence of Ig Heavy chain + surrogate light chain + Igalpha and Igbeta signalling molecules
        
        Immature B cell: produces IgM
        
        Mature B cell: produces IgD and IgM
        
        Ignorance
- - - - Lymph nodes are connected to circulation
        
        Sites where lymphocyte circulating in blood can meet dendritic cells circulating in lymphatic fluid :warning:
        
        BLUE zone B cell follicles
        
        Have Follicular dendritic cells
        
        Multiply and divide into plasma cell :warning:
        
        Morph into a memory cell :warning:
        
        Present antigens in the form of icosomes
        
        RED zone T cell zone
        
        Have the rest of the dendritic cells