Secondary Lymphoid Organs and Lymphocyte Trafficking

7 important questions on Secondary Lymphoid Organs and Lymphocyte Trafficking

(Secondary lymphoid is) highly organised and acts as a filter for the lymph

Zie de afbeelding


  • T and B cells enter through HEV (from blood) or via the lymph
  • Antigen (opsonized) can enter via the lymph or already inside DCs
  • Lymph comes in through Marginal sines which is carpeted with macrophages (eat antigens)



T cell independent activation of B cells

  • Early in infection. Antigens decorated with complement end up in the lymph node
  • follicular DCs catch them and present them to B cells
  • once a B cell recognizes the antigen: proliferation and activation --> IgM
  • But also uptake of the antigen and MHC II presentation
  • Move to T cell zone, no Cell, B cell apoptosis
  • Move to T cell zone, T cell that is activated by same antigen, survival of the B cell

T cell-dependent activation of B cells

  • Antigen presenting cells (DCs) MHC II present antigen to T cells, these T cells proliferate and differentiate
  • T cells become Th1, Th2 etc
  • Upregulate CD40L and
  • secrete cytokines
  • which give the B cell class switch signals
  • Plasma cell formation and correct Ig produced.
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Kenmerken/eigenschappen van secondary lymphoid organs

  • Brings lymphocytes and antigen presenting cells together
  • maximises the activation
  • each lymphoid organ drains a specific site (spleen--> blood) and the immune cells found there are most likely to respond to the antigens present at that site


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What is the advantage of T cell independent activation over T cell dependent activation?

T cell independent activation is quicker, because the B cell do not have to wait for the T helper cell to become active. Furthermore, T helper cells are specialised in recognising protein, but many invaders have carbohydrates of fats on their surface. These invaders can be recognised by the T cell independent activated B cell.

What is an immunological synapse?

The immunological synapse is the clustering of TCRs and co-receptors between T cells and dendritic cells

What are the two functions of Th cells ar regards to the functioning of CTLs?

The Th cells help the CTLs to kill more efficiently. Moreover, Th cells are needed to make memory CTLs

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