cells & tissues of the immune system Flashcards

1
Q

primary lymphoid tissues

A

where immune cells originate and develop:

  • bone marrow
  • thymus (site of T cell maturation)
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2
Q

secondary lymphoid tissues

A

where the immune response is activated:

  • lymph nodes
  • tonsils
  • spleen
  • mucosa-associated lymphoid tissue
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3
Q

myeloid WBCs

A
  • neutrophils
  • eosinophils
  • basophils and mast cells
  • antigen-presenting cells (macrophages and dendritic cells)

* RBCs and platelets also come from myeloid precursors

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4
Q

lymphoid WBCs

A
  • B cells
  • T cells
  • NK cells
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5
Q

Neutrophils

A
  • primary cell of the innate immune system
  • ingest and kill pathogens, produce myeloperoxidase, do not present antigen
  • maturation: blast -> myelocyte -> band -> neutrophil
  • release of granulocyte colony stimulating factor during infection leads to increased myeloid precursors in the peripheral blood as bone marror mobilizes neutrophils
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6
Q
A

neutrophil

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7
Q
A

eosinophil

bilobed nuclei, bright pink granules

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8
Q

eosinophils

A
  • innate immunity
  • stimulated by IL-5
  • increased in parasitic diseases and hypersensitivity
  • attach to surface of nematode larvae by binding IgG and IgE produced by B cells (antibody dependent cell mediated cytotoxicity)
  • not antigen presenting
  • maturation: precursor -> myelocyte -> eosinophil
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9
Q
A

basophil

(lots of dark granules)

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10
Q
A

mast cell

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11
Q

basophils and mast cells

A
  • basophils in peripheral blood; mast cells in tissues
  • key function = inflammation
  • involved in anaphylaxis: receptors for Fc portion of IgE

release histamine and other cytokines

  • innate immunity: TLRs on surface recognize PAMPs
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12
Q
A

monocyte

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13
Q
A

macrophage

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14
Q

monocytes and macrophages

A
  • monocytes circulate in blood; macrophages are activated in tissues
  • innate immunity: phagocytosis of pathogens and debris; cytokine production
  • produce IL-1, TNF, IL-12
  • adaptive immunity: professional antigen presenting cells
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15
Q

tissue resident macrophages

A
  • alveolar mΦ (lung)
  • kuppfer cells (liver)
  • microglia (brain)
  • red pulp mΦ (spleen)
  • tingible body mΦ (germinal center)
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16
Q

antigen presenting cells

A
  • mΦ, dendritic cells, B cells
  • link innate and adaptive immunity
  • express pattern recognition receptors (TLRs) that bind PAMPs
  • MHC class II on cell surface for antigen presentation:
    1. engulf pathogens
    2. digest proteins
    3. express peptides in MHC II
17
Q

dendritic cells

A
  • antigen presenting cells
  • finger like projections help present antigen
  • induce T cell and primary antibody response: migrate to lymph nodes to present antigen to CD4+ T cells
  • located under skin (langerhans cells) and in mucosa
  • lineage: complicated…can be myeloid and lymphoid
18
Q

B cells

A
  • adaptive immunity: involved in antibody-based humoral immunity
  • CD19+ and CD20+
  • differentiate into plasma cells that secrete antibodies
  • maturation occurs in bone marrow: pro-B cell => pre-B cell => immature B cell
19
Q
A

lymphocyte

20
Q
A

plasma cell

pale area = golgi….very active protein synthesis for antibody production

21
Q

plasma cells

A
  • come from B cells
  • CD38 and CD138
  • produce and secrete antibodies
22
Q

T cells

A
  • majority of lymphocytes in circulation
  • adaptive immunity
  • cell mediated immunity: recognize protein antigens (presented by MHC) and kill virus infected cells, tumor cells, foreign cells
  • originate in bone marrow and maturation occurs in thymus: CD3+ => CD4+ helper and CD8+ cytotoxic
23
Q

NK cells

A
  • innate immunity
  • directly kills infected cells and tumor cells:
    1. recognition of a cell’s lack of MHC class I
    2. binding
    3. secretion of cytotoxic granules
  • CD56+ and CD16+
  • do not express specific receptors
24
Q

lymphatic stroma (lymph nodes, nodules, and spleen)

A
  • type III collagen reticular fibers produced by reticular cells
  • loose connective tissue
25
Q

thymus stroma

A
  • branching, interconnected epithelioreticular cells (6 types)
  • come from embryonic branchial pouch 3
  • stroma, but also involved in T cell education: secrete interleukins, colony stimulating factor, and interferon to promote expression/deletion of CD antigens on T cell surfaces
  • types 2 + 5: present self and foreign antigens to T cells at an early stage => must recognize antigens to go from cortex to medulla and continue maturation
  • type IV forms thymic (Hassall’s) corpuscles: large, pink staining, concentric curls of keratinized epithelioreticular cells that secrete interleukins
26
Q

lymph nodules

A
  • dense clumps of B cells in a meshwork of reticular fibers
  • found in diffuse tissue of lymphatic organs or in loose connective tissue of GI, respiratory, and urinary tracts
  • not considered organs b/c no capsule
  • during immune response: geminal center stains lighter due to larger cells with more cytoplasm and euchromatin (due to replication)
27
Q

lymph nodes

A
  • small organs along lymphatic vessels that “filter” lymph to increase change of antigens encountering mΦ’s and lymphocytes
  • structure:
  • connective tissue capsule
  • outer cortex with nodules (B cells)
  • deep cortex with diffuse T cells
  • inner medulla with T cells
  • trabeculae = connective tissue going from capsule to emdulla
28
Q

pathway of lymph through lymph node

A
  1. afferent lymphatics
  2. subcapsular sinus (simple squamous epithelium)
  3. trabecular sinus
  4. medullary sinus
  5. efferent lymphatics exiting at hilium
29
Q

pathway of lymphocytes from blood through the lymph node

A

entry/exit through high endothelial venules

*simple cuboidal epithelium

30
Q

spleen function

A
  • platelet resevoir
  • destroys defective/aged RBCs (red pulp)
  • recycles iron
  • immune reactions to blood borne antigens by B and T cells (white pulp)
31
Q

spleen structure

A
  • dense connective tissue capsule
  • red pulp
  • splenic sinuses = venous channels with long endothelial cells with gaps bewteen them, parallel to axis of sinus, perpendicular to strips of basal lamina, allow blood cells to pass through walls of sinus
  • splenic cords = meshwork of reticular cells and fibers among dense aggregations of RBCs and mΦs
  • white pulp
  • periarterial lymphatic sheaths = dense aggregates of T lymphocytes + B lymphocyte nodules surrounding central arteries
  • spelnic artery enters at hilium => trabecular arteries => central arteries
  • connective tissue trabeculae into interior
32
Q

open system of splenic blood flow

A
  • central arteries => sheathed capillaries surrounded by macrophages => splenic cords where blood percolates through reticular meshwork and macrophages do their thing => splenic sinuses => trabecular veins => splenic vein

*other mammals have a closed system where arterioles => splenic sinuses

33
Q

thymus function

A
  • T cell maturation
34
Q

thymus structure

A
  • decays/turns into fat over time after immune system develops
  • connective tissue capsule
  • interconnected lobules
  • cortex has densly packed T cells (stains darker; basophilic)
  • medulla has less densly packed cells and geminal centers
  • trabeculae carry blood; no sinuses for lymph