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Bloc F - Defense > Mar22 M1-Functional Morphology Lymphoid > Flashcards

Mar22 M1-Functional Morphology Lymphoid Flashcards

1
Q

primary or central lymphoid organs

A

bone marrow and thymus

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2
Q

secondary or peripheral lymphoid organs

A

lymph nodes, spleen, GI mucosa, MALT (mouth, GIT except stomach, tonsils, etc.)

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3
Q

where are lymphoid cells come from + 3 steps that happen there (4 Ps)

A

bone marrow: pluripotential stem cells to progenitor (lymphoid) cells (lymphoid, myeloid and erythroid progenitor) to precursor B or T lymphoblasts. 4th P is for pelvis, site of BM bx

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4
Q

what B-lymphoblasts do

A

in the BM, mature into naive B cells that then go to peripheral lymphoid organs

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5
Q

what T-lymphoblasts do

A

from BM, go the thymus and mature there. then go to peripheral lymphoid organs

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6
Q

B and T lymphoblasts def

A

precursors in the marrow and the thymus (T lymphoblasts start in BM then move to thymus)

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7
Q

centroblasts def

A

mature B cells in the germinal center of lymph nodes

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8
Q

B and T immunoblasts def

A

cells that, after exposure to Ag, give rise to plasma cells and B memory cells (from B immunoblasts, includes naive B cells?) and T memory cells (from T immunoblasts)

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9
Q

important role of germinal center

A

in B cell response, important for a lasting Ab production.

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10
Q

charact of cells in the germinal center

A

very actively proliferating with many mutations (fertile bed for development of malignancy). bc of role of lasting Ab production

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11
Q

acquired immune deficiency examples and one consequence

A
  • HIV
  • post transplant immunosuppression
  • predisposes to malignancy
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12
Q

important concept in immune and blood malignancies

A

each malignancy has a normal cell counterpart

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13
Q

what cells give rise to naive (but MATURE) B cells (CD20+)

A

B-lymphoblasts (precursors) (are hematogones, meaning normal round cells)

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14
Q

naive mature B cells location in the body

A
  • FEW in marrow and blood

- MANY migrate to secondary peripheral lymphoid organs via blood stream

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15
Q

lymphoblasts function (important thing they do)

A

undergo VDJ rearrangerements to generate a repertoire of Igs

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16
Q

2 functions of the thymus

A
  1. maturation and selection of T lymphoblasts (mature naive T cells)
  2. induction of central tolerance by regulatory T cells to prevent autoimmunity
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17
Q

T-lymphoblasts where they go in the thymus

A

from BM, go to thymic epithelial space. there, proliferate with the help of thymic epithelial cells

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18
Q

2 spaces of the thymus

A
  • central lymphoid space

- peripheral perivascular space

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19
Q

2 components of the central lymphoid space of the thymus and their cells

A
  • cortex: 1.large cortical epithelial cells 2. macrophages 3. T-lymphoblasts
  • medulla: 1. small mature appearing lymphocytes (mature) 2. epithelial cells 3. mature B cells
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20
Q

function of the large cortical epithelial cells in the cortex (thymus)

A

APCs secreting cytokines. have desmosomes and form cortico-medullary barrier.

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21
Q

function of the macrophages in the cortex (thymus)

A

APCs. phagocytosis of apoptotic cells

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22
Q

function of T-lymphoblasts in the cortex (thymus) and 2 other names

A

T-lymphoblast = thymocytes = precursor T-cells
*fct = make mature naive T cells.
(thymocytes are initially double negative then double positive CD4+ CD8+)

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23
Q

function of small mature appearing lymphocytes of the medulla (thymus)

A

T cell immunophenotype (TdT-, CD3+, CD4 or CD8+)

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24
Q

function of epithelial cells in the medulla (thymus)

A

small, spindle-shaped, form *Hassall’s corpuscules

25
Q

function of mature B cells in medulla (thymus)

A

associated with epithelial cells + may play role in T-cell differentiation.

26
Q

steps of T cells selection

A
  1. CORTEX: POSITIVE selection: only T cells with functional TCRs that see MHC 1 and 2 are kept
  2. MEDULLA: NEGATIVE selection: only T cells that DON’T bind tightly to self-Ags are kept
27
Q

peripheral perivascular space of the thymus: cells there

A

mature naive T lymphocytes that travel to lymph nodes and other peripheral lymphoid sites and blood

28
Q

compartments of the lymph node (4)

A
  1. cortex: contains many B follicles (inner germinal center and outer mantle zone) separated by interfollicular areas
  2. paracortex (between cortex and medulla)
  3. medulla = where lymph flows
  4. subcapsular sinus (around the cortex) = 1st place of metastasis in metastatic CA
29
Q

other name for mantle zones (outer B follicle)

A

B zone

30
Q

2 lymph node stages and how it relates to B follicles

A

quiescent node = no Ag stim

with Ag stim, mantle zone (naive B cells) forms the germinal center (naive B cells)

31
Q

cells in follicles, germinal centers

A
  1. B-lymphocytes in various stages of activation (centrocytes, centroblasts). naive B cells is if didn’t see Ag
  2. helper CD4+ T cells
  3. follicular dendritic cells (APCs)
  4. macrophages (tangible body macrophages) (phagocytosis of B cells with low Ag affinity)
32
Q

cells in the lymph node paracortex

A
  1. T cells in various stages of activation MOSTLY

2. interdigitating dendritic cells (APCs)

33
Q

high endothelial venules of the lymph node: location and fct

A
  • specialized entry points for blood lymphocytes coming from BM and thymus
  • venules entering lymph node at level of the T cell zone which is in the middle of the lymph node
34
Q

cells in high endothelial venules

A

lot of endothelial cells

35
Q

compartments (and their cells) of the lymph node medulla

A
  • medullary cords (B and T cells + plasma cells)

- medullary sinuses (many macrophages for filtration + lined by endoth cells)

36
Q

2 compartments of the germinal center and their cell types

A
  • dark zone (centroblasts: B cells rapidly proliferating and mutating their Ig. Bc immune resp started, lymph node stopped being quiescent, germinal center being made)
  • light zone (centrocytes: centroblasts that STOPPED proliferating and that are subject to selection by follicular helper T cells with help of follicular dendritic cells)
37
Q

marginal zone of the lymph node (near germinal center): cells in there

A

immunoblasts (large cells giving rise to plasma and memory c) + plasma + memory B cells

38
Q

PRIMARY immune response location in lymph node + cells

A
  • paracortex (OUTSIDE GC)
  • T cells activate naive B cells, form proliferating B-immunoblasts, short lived IgM plasma cells + NO memory cells
  • Some IgM+ immunoblasts go to PRIMARY B follicle to initiate 2ndary resp
39
Q

SECONDARY immune response location in lymph node + cells

A
  • GC
  • T cell activ of naive B cells, make proliferating centroblasts, then centrocytes then immunoblasts then these make long-lived IgG plasma cells + memory cells
40
Q

4 steps of GC reaction to Ag

A
  1. proliferation
  2. somatic hypermutation of Ig V region genes to increase affinity of Ab for Ag
  3. Selection
    4 Differentiation
41
Q

proliferation step of GC reaction to Ag

A

B centroblasts proliferate a lot. dark zone.

  • apoptosis by macrophages
  • BCL2 (anti-apoptotic gene) inactivated
42
Q

selection step (3) step of GC reaction to Ag

A

centroblasts to centrocytes in light zone of GC. class switch to IgA or IgG. apoptosis of low affinity ones. (GC T cells check that)

43
Q

differentiation step (4) of GC reaction to Ag

A

immunoblasts (from centrocytes) form plasma and memory cells

44
Q

location of B-immunoblasts, plasma cells and memory cells after differentiation step

A

in marginal zone, OUTSIDE of GC

45
Q

origin of plasma cells

A

primary immune response = from naive B cells, in paracortex (short-lived, IgM)
secondary response = from immunoblasts, in light zone of GC

46
Q

locations of plasma cells

A
  • paracortex and GC light zone

- move to lymph node medulla, BONE MARROW and other sites

47
Q

function of plasma cells

A

secrete one specific Ab with one light chain (kappa or lambda) and one heavy chain type

48
Q

IHC profile of plasma cells

A

POSITIVE: CD27++ (also, memory cells are +), CD138+, CD78, IL-6 R
NEGATIVE: CD19, CD20***

49
Q

IHC profile of plasma cells

A

POSITIVE: CD27++ (also, memory cells are +), CD138+, CD78, IL-6 R
NEGATIVE: CD19, CD20***

50
Q

2 main compartments of the spleen

A

white pulp (20%) and red pulp (80%)

51
Q

structure of the white pulp

A
  • lymphoid nodules

- periarteriolar lymphoid sheaths (PALS)

52
Q

structure of the red pulp

A
  • blood filled sinusoids

- splenic cords

53
Q

lymphoid nodules of the white pulp description

A

mantle zone + margina zone (plasma + memory) around. if active bc exposed to Ag, GC in middle of mantle zone

54
Q

splenic blood flow (red pulp function)

A
  • to feed areas of immune cells

- central arteriole to penicillar arteriole to sheathed capillaries

55
Q

2 circulations in splenic red pulp, blood flow

A
  • closed circulation via splenic sinuses

- open circulation through splenic cords and reenter via walls of the sinuses

56
Q

goal of open circulation in spleen red pulp

A

circulation in reticular fibers and splenic cords = trap red cells that can’t get through or that aren’t in good shape

57
Q

tissues that form or contain MALT

A
  • Waldeyer ring in the whole pharyngeum (naso and oropharynx, tonsils, adenoids)
  • GIT (SI and colon. appendix. Peyer patches in ileum)
  • tracheobronchial tree
  • acquired MALT in stomach or site of chronic inflam
58
Q

MALT (Peyer’s patches for example) structure

A

marginal zone, mantle zone and ALWAYS HAVE A GERMINAL CENTER (bc always see Ags and always activated)

59
Q

MALT function

A
  • defense of internal passages against foreign Ags
  • mainly IgA
  • secondary immune response to microbes in oral cavity, gut, etc.
  • appendix = lymphoid + may serve as reservoir of beneficial bacteria for replenishing after diarrhea

Bloc F - Defense (57 decks)

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