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PMI 126 - Lecture 4

PMI 126 - Lecture 4 - PMI 126 Lecture 4 Organs of The...

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PMI 126 – Lecture 4 Organs of The Immune System All the fluid (containing soluble proteins associated with the immune system) of body drains down through lymphatic system. And go through lymph node and out of lymph node, then back into blood. granulocyte never leave the blood unless there is tissue insult (infection) greater the insult = greater the release of WBC Primary Lymphoid Organs: with production and maturation of lymphocytes Bone marrow: - where B cells develop and grow up. - where WBCs are created. - Can mount an immune response Thymus: - where T cells mature - located behind the heart and all the way to the neck - become smaller as you age. (atrophy) o right after birth, all the lymphocytes are naïve & no one has been selected for memory yet. o The ability to generate immune responses to new antigens is less and less as you age. Due to the lost of thymus function Due to fall of memory (previously) and not a lot of room left Nature exposure keeps the memory to high level - structure: o cortex: where pre-T cells first come in where pre-T cells undergo positive selection (only the one that interact with “self” MHC protein is selected = no apoptosis) o medulla: where T cells migrated from cortex T cells undergo negative selection (the ones that bind to MHC protein too strongly, because they can cause autoimmunity) * after the selection, naïve T cells (the one survive after 2 selections) come out of the thymus to the blood. Only 2% makes it. These T cells circulate in the blood of the body until they encounter the specific antigen. If they don’t bind any antigen, they undergo apoptosis. - Immune response is NOT generated in the thymus Secondary Lymphoid Organ: lymphoid organ that mount immune response - Through out the periphery. - lymph nodes, spleens (for blood-borne pathogen), and organized lymphoid tissue (MALT) Lymph node: - afferent lymphatic vessels (bring the lymph (cells and fluid) into the node) o then enter into the paracortex area = T-cells dominant! o Most of the B cells are at the cortex. - Dendritic cells carrying the antigen (or its pieces) to paracortex via afferent lymphatic vessels o Every T-cells then investigate the antigen until the receptor matches. o The specific T-cell recognizes the antigen, it’s activated .
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