Histology - Immune System Presentationtbl.med.yale.edu/files/histology_of_the_immune_system/... ·...
Transcript of Histology - Immune System Presentationtbl.med.yale.edu/files/histology_of_the_immune_system/... ·...
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What we’ll talk about…
• Lymph nodes and the development of humoral immune responses
• Red pulp and white pulp in the spleen
• Thymus and T-cell development
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An adaptive immune response requires direct interaction between specific immune cells.
T-Cell
B-Cell
Antigen-presenting Cell
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Lymph Node
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Lymph nodes facilitate interactions between antigen, antigen-presenting cells and lymphocytes.
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The lymph node is structurally and functionally divided into a cortex, paracortex and medulla.
MedullaParacortex
Secondary Lymphoid Follicle
Cortex
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Lymph enters through the capsule and then flows through sinuses in the cortex and medulla.
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Macrophages beneath the subcapsule sinus capture antigen from lymph.
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The capsule contains afferent lymphatic vessels that delivers lymph from peripheral tissues.
Lymphatic Vessel
Capsule
Subcapsular Sinus
Parenchyma - Cortex
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Secondary lymphoid follicles contain a germinal center with maturing and dividing B-cells.
T-Cell Zone
B-Cell MantleLymph
Germinal Center
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B-cells find antigen in the light zone of germinal centers and divide in the dark zone.
Light Zone
Dark Zone
T-Cell Zone
Cortex
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The paracortical region contains T-cells and venules where lymphocytes enter lymph nodes.
High Endothelial Venule
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The medulla contain macrophages and B-cells arranged in cords and sinuses that contain lymph.
Cortex
Medullary Sinus
Medullary Cord
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Spleen
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The spleen forms immune responses in white pulp and filters red blood cells in red pulp.
Red Pulp White Pulp
Trabecular Artery
Capsule
Trabeculae
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Blood flows through white pulp and then some is released into red pulp.
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White pulp contains germinal centers with B-cells surrounded by T-cells and resting B-cells.
Red Pulp
Central Artery
Germinal Center
Mantle Zone
PALS
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Red pulp contains venous sinuses that filter old and malformed red blood cells.
Endothelial Cell
Sinus
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Thymus
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The thymus is arranged into lobules each with an outer cortex and inner medulla.
MedullaCortex
CapsuleSepta
Lobule
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Thymocytes enter at cortical-medulla border, migrate to the outer cortex and undergo maturation.
Cortex
Medulla
2. Migrate
3. Mature
1. Thymocytes Enter
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The cortex is the site of positive selection and contains immature and maturing thymocytes.
Mitotic Cell
Cortical Epithelial Cell
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The medulla is the site of negative selection of thymocytes.
Hassall Corpuscle
Epithelial Cell
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Take home messages…
• Lymph nodes facilitate interactions between B-cells, T-cells and antigen to generate a humoral immune response
• The spleen filters old and damage red blood cells and generates immune responses against blood-borne antigen.
• The thymus facilities development of T-cells through positive and negative selection.