BIOL-K 338 Lecture 3: Tissues Notes

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Lecture 3
Lymphoid Tissues
o Primary Tissues: give rise to cells of the immune system
o Secondary Tissues: provide organized sites for antigen capture and presentation to cells and for
interaction between different cells of the immune system
Cell expansion during activation, very specific
Primary Lymphoid Tissues
o Bone Marrow
Site of origin of all blood cells
Site of maturation of B cells (25% completely mature in bone marrow)
Hematopoietic stem cells: less than 0.005% cells in bone marrow
Blood cells in various stages of maturation
Stromal cells support growth and maturation of hematopoietic
o Thymus
Maturation of T-cells
Early T progenitor cells migrate from bone marrow to thymus
Proliferate and differentiate
Most thymocytes die in thymus (only some mature to T-cells and move)
Right above heart
Reaches max size during adolescence and shrinks (involutes) during aging
No thymus= no mature T cells
Nude ie eed oe arro trasplats
DiGeorge Syndrome: human impaired thymic development. Leads to deficit of
mature T cells and consequent immune deficiency (immune-deficient)
Secondary Lymphoid Tissues
o Cells designed to expand
o Lymph nodes, spleen, mucosal-associated lymphoid tissues (MALT), GALT (gut associated
lymphoid tissue), BALT (bronchi associated lymphoid tissue)
o Lymphadenopathy: swelling of lymph nodes
Draining lymph nodes attached to lymphatic vessels (thin, valved, flexible)
No pressure gradient (muscles move lymph)
No movement causes lymph to pool in sick people
o Spleen: not connected to lymphatic vessels (serves as blood filter)
o Adenoids: specific type of tonsil
Brain and Lymphatic Vessels
o Brain is not as immune privileged as once thought
Some lymphatic vessels, but works differently due to BBB
Lymph Nodes
o Lymph flows afferent dirty lymph, flows out efferent w/ lots of antibodies
o Follicles: active B cells (and some helper t cells)
o Paracortex: t-cells
o Medulla: center of cells
o Cortex: most superficial (innervating blood vessels)
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