Lecture 32: Lymphoid organs Flashcards

1
Q

primary lymphoid organs

A

bone marrow, thymus

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2
Q

secondary lymphoid organs

A

lymph nodes, spleen, MALT

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3
Q

MALT

A

mucosa associated lymphoid tissue

  • Diffuse populations of lymphoid cells in the mucosa
  • Lymphoid follicles of the GI, respiratory and genitourinary tracts
  • Peyer’s patches of the ileum
  • Tonsils
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4
Q

sources from lymphocytes

A

bone marrow (ULTIMATE)

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5
Q

bone marrow makes

A

1) T cell precursor that goes to thymus where they mature into helper and cytotoxic
2) Mature B cells
* both end up in secondary lymphoids

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6
Q

what do helper t cells do

A

activate cytotoxic t cells

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7
Q

what to cytotoxic t cells do

A
  • Kill tumor cells, virus-infected cells, etc by contact

- Cell-mediated immunity

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8
Q

what do b cells transform into

A

plasma cells

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9
Q

what do plasma cells do

A

Kill by secretion of antibodies
Humoral immunity
(FROM B CELLS!!!!)

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10
Q

where is thymus found

A

superior mediastinum

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11
Q

how many lobes to thymus

A

2

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12
Q

what happens to thymus at puberty

A

undergoes involutions

most active frombirth to puberty

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13
Q

function of thymus (3)

A

1) Provides an environment where T cell precursors proliferate, mature and acquire their immunocompetence.
2) Supplies mature T cells to secondary lymphoid organs.
3) Secretes hormone-like substances which stimulate T cell proliferation and maturation.

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14
Q

major cell types in cortex of thymus

A

large lymphocytes (immature T)
small lymphocytes (maturing T)
epithelial reticular
macrophages

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15
Q

clonal selection is another term for

A

maturation

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16
Q

clonal selection

A

outer cortex large immature lymphocytes proliferate and divide, move through inner to corticomedullary junction. (React with body antigen as moving through or those that cant react die by apoptosis – 95%!!)

17
Q

positive selection

A

t cells that recognize non self antigens become mature (helper and cytotoxic) less than 5%

18
Q

negative selection

A

React with body antigen as moving through or those that cant react die by apoptosis – 95%!!

19
Q

Apoptotic T cells are phagocytized by

A

macrophages - contribute to negative selection

20
Q

what does negative selection do

A

prevents development of autoimmune disease

21
Q

what are epithelial reticular cells linked by

A

desmosomes

22
Q

epithelial reticular cells (what do they do)

A

present antigens to maturing T cells

instruct/educate maturing t cells to react or not react with antigens

23
Q

thymulin, thymosin, thymopoietin

A

● Polypeptides secreted by epithelial reticular celThymic hormone-like substances

24
Q

hassall’s corpuscle

A

histo marker for thymus
first appear in fetal life and increase in number and size after
concentric layers of epithelial reticular cells

25
hassall's corpuscle histo description
Concentric layers of epithelial reticular cells that appear eosinophlic, keratinized and degenerative * can secrete cytokines and phagocytose
26
thymic involution
thymus of elderly adult showing lymphoid tissue separated by adipose tissue already have enough secondary t cells in organs to keep immunity