Lecture 4 Lymphocytes Flashcards
Where and what % of lymphocytes are distrubited in the body (6)
Lymph nodes 40% Other tissue 25% Spleen 13% Bone marrow 10% Intestine 10% Blood 2%
What are lymphoid organs and what are the primary and secondary lymphoid organs
Lymphoid organs is where APCs are taken to where lymphocytes are
Primary Lymphoid organs regulate production and differentiation of lymphocytes and self reactive cells are removed (Thymus, Peyers patches and bone marrow)
Secondary lymphoid organs are tissues where antigen processing occurs and lymphocytes response to antigen (tonsils, spleen, bone marrow, peyers patches)
Where are T cells produced and where are B cells produced
Bone marrow make stem cells, which goes to peyers patches, thymus or stay in bone marrow. B cells (memory and plasma cells) are made in bone marrow. T cells (helper, cytotoxic and memory) are made in the thymus.
Where does fetal hematopoiesis start and finish
Starts in yolk sac
Ends in bone marrow
Describe how B lymphocytes are made in the bone marrow
B lymphocytes develop in contact with the stromal cells of the bone marrow
Describe how T lymphocytes are made in the thymus
T cells develop initially in bone marrow then migrate to thymus
T cells are made by positive and negative selection in thymic cortex and medulla
Describe positive and negative selection of T cells in thymus
T cell receptor affinity of binding with MHC peptides drives positive and negative selection
If the pre T cells react strongly with self antigens or dont react with self MHC, they are killed
If the pre T cells dont react with self antigens and react with self MHC then they are matured
Describe lymph nodes as lymphoid organs
Lymph nodes are the most highly organised secondary lymphoid organs. Major site of antigen-lymphocyte interactions. Cortex major site of B cell responses, paracortex full of T cells and medulla rich in APCs and macrophages
Describe the spleen as a lymphoid organ
Secondary lymphoid organ. Filters antigens from blood Red pulp - red cell storage and hematopoiesis
White pulp - lymphoid tissue
Where are antibodies made?
Primary response - Lymph nodes and spleen
Secondary response - Bone marrow
More antibody made in secondary response (bone marrow)
Describe mucosa associated lymphoid tissue (MALT) as a lymphoid organ
Secondary lymphoid organ. Layer of defence against infection at mucosal and epithelial layers
Organises responses to antigens that enter mucosal tissues
What are the four receptors on B cells
Immunogoblin receptors
Cytokine receptors
Complement receptors
Antigen receptors
What are the three receptors on T cells
Antigen - receptor complex (MHC receptors CD4 and CD8)
Complement and cytokine receptors
Transport receptors
What are the important T and B cell receptors
B cells have a B cell receptor (BCR) composed of IgM or IgD plus a signal transduction molecule. BCR binds to free Ag
T cells have TCR. T helper cells have a TCR associated with CD4 and cytotoxic T cells have one associated with CD8. T cells can only bind Ag presented with MHC molecule
Describe natural killer cells
Part of innate immune response, no TCR. Important for control of viral infections and can recognise and kill stressed/old cells.
