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MEDSCI 314 > Lecture 3: Components of the immune system 1 > Flashcards

Lecture 3: Components of the immune system 1 Flashcards

1
Q

Where do WBC originate from?

A

WBC of the immune system originate from the red bone marrow

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2
Q

Describe cell movement post hematopoesis;

A

Cells migrate through bones VENOUS SINUS’ to guard peripheral tissues, circulating in the blood and lymphatic system.

During this time cells receive signals via their receptors that contribute to their survival.

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3
Q

Describe the first degree of heamotopeosis;

A

Hemapoetic stem cells divide symmetrically or assymetrically - the later which gives rise to the Multipotent progenitor which gives rise to;

  • Common myloid precursor (CMP)
  • Common lymphoid precursor (CLP)
  • Mast cell progenator (these directly give rise to mast cells)
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4
Q

What do CMP give rise to?

A

CMP

  • Megakaryocyte/erythrocyte precursors(MEP)
  • Granulocyte/monocyte precursor (GMP)

MEP

  • Megakaryocyte
  • Erythrocyte

GMP

  • Basophil
  • Eosinophil
  • Neutrophil
  • Monocyte
  • Dendritic Cell
  • pDC

These are the cells of the innate immune system

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5
Q

What does CLP give rise to?

A

CLP

  • B cell
  • T cell
  • NK cell
  • NKT cell
  • DC
  • pDC
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6
Q

What is the function of monocytes?

A

They are located in the circulation and continually differentiate into macrophages in the tissue.

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7
Q

Describe the function of dendritic cells;

A

Dendritic cells are specialized myeloid cells that take up antigen, process it and present it to lymphocytes

(APC)

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8
Q

What are the two classes of lymphocytes?

A

B cells ; which when activated differentiate into plasma cells that produce antibodies

T cells ; Involved in killing infected cells (Tk) and regulating adaptive immunity (Th)

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9
Q

What is remarkable about lymphocytes?

A

They are capable of amounting an immune response against virtually any pathogen b/c
- Each individual lymphocyte matures bearing a unique variant of a prototype antigen receptor so that a population of T and B lymphocytes collectively bears a huge repertoire of receptors that are highly diverse in their antigen binding sites

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10
Q

Describe the receptors on lymphocytes;

A

B cells: Antigen receptor is a membrane bound form of antibody

T cell: Antigen receptor is the T cell receptor

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11
Q

Describe the time course of immune developmental and location;

A

Primitive wave of hematopoesis in embryonic structures

~5 months mainly liver contributing and some spleen

At birth bone marrow is in full swing of production and Only contributor.

Heamotopoesis declines with age but vertebrae is biggest contributor life long

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12
Q

What is a distinctive feature of immune cell distribution?

A

Compartmentalisation

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13
Q

Describe the immune cells compartmentalised in the bone marrow;

A

HSCs

Early hematopoetic progenators

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14
Q

what are the immune cells compartmentalised in the blood?

A

Monocytes
Neutrophils
Basophils
Erythrocytes

B and T cells

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15
Q

what are the immune cells compartmentalised in the tissues?

A 
Macrophages
DC
Mast Cells
NK cells
NKT cells
Esinophils

B and T cells

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16
Q

What is unique about macrophages?

A

They have a spectrum of functions therefore this is tissue/context dependant as is their name.

17
Q

What happens to DC over time?

A

As they become mature and activated, receptor expression and morphology changes to optimise function

18
Q

Where do B cells originate from?

A

B lymphocytes originate from lymphoid progenitors in bone marrow

19
Q

Describe b cell development;

A

1) Generation of b cell receptors in bone marrow
- b-cell precursor rearranges its immunoglobulin genes

2) Negative selection in the bone marrow
- Immature b cells are tested against self cell receptor antigens in bone marrow, reactive ones removed/ neglected

3) B cells migrate to the peripheral lymphoid organs
- Mature B cells that bind to specific antigen become activated

4) Antibody secretion and memory cells found in bone marrow and lymphoid tissues
- Activated B cells give rise to plasma cells and memory cells

20
Q

Describe T lymphocyte development;

A

1) T-cell progenitors develop in the bone marrow and migrate to the thymus
- T-cell precursor rearranges its t cell receptor genes in the thymus

2) Positive and negative selection in thymus
- (central tolerance) Immature T cells that recognise self MHC recieve signals for survival (+ive selection). Those that react strongly with self antigens are removed (-ive selection)

3) Mature T cells migrate to the peripheral lymphoid organs
- Mature T cells encounter foreign antigens in the peripheral lymphoid organs and are activated

4) Activated T cells migrate to site of infection
- Activated T cells proliferate and migrate into peripheral sites to eliminate infection

21
Q

Describe t lymphocyte development in the thymus;

A

1) Positive selection, MHC recognition occurs in thymic cortex
2) Negative selection occurs at the cortical medullar junction

(thymic lobule can be divided into cortex and medulla)

22
Q

What are some primary lymphoid organs?

A

The thymus and bone marrow are primary lymphoid organs b/c they are places where lymphocytes arise and mature.

These are then exported to other lymphoid organs (secondary or peripheral lymphoid organs) where they act in immune responses

23
Q

What are some secondary lymphoid organs?

A

Spleen
Lymph node
Gut Associated Lymphoid Tissue (GALT)
- Tonsils, adenoids, peyers patches

24
Q

Describe the structure of the immune system;

A

Collection of organs connected together by blood vessels and lymphatic vessels.

Cells and molecules of the immune system flow into and out of the lymphoid organs around the body.

These can leave the circulation through the vessel walls and enter the tissues.

Cells, molecules, microbes drain back into the immune system through lymphatic vessels

25
Q

Where to most lymphocytes reside?

A

Mostly in the lymphatic organs, 10% in circulation

26
Q

Describe lymphatic circulation;

A

Cells bathed in nutrient rich interstitial fluid (blood plasma)

Under pressure plasma leaks into the EC space.

90% plasma returns to circulation via venules. 10% drains through tissues and enters the lymphatic capillaries becoming lymph.

Lymphatic capillaries connect to progressively larger vessels. Which in turns connects to the thoracic duct or right lymphatic duct.

Valves maintain lymph flow direction

27
Q

As lymph enters the lymphatic circulation what does it pass through?

A

Passes through lymph nodes (major site of interaction between lymphocytes with antigen during primary adaptive immune response

28
Q

What is the function of the peripheral lymphoid organs then?

A

Specialized to trap antigen bearing DC to allow initiation of adaptive immune responses and provide signals that sustain recirculating lymphocytes.

29
Q

Describe lymphocyte and antigen meeting location…

A

Antigen and lymphocytes encounter each other in the peripheral lymphoid organs

Lymphocytes are continually recirculating through these tissues

Antigen processed and presented via DCs

Adaptive immune response (primary or secondary)

Lymphoid organs generate environment for immune response

30
Q

Whats a key feature of lymphatic circulation?

A

It is dynamic

31
Q

What is lymphocyte recirculation;

A

Lymphocyte recirculation; Process whereby resting T,B cells migrate continually b/w the blood and the secondary lymphoid tissues

32
Q

What does recirculation solve?

A

Getting the lymphocyte to the right place at the right time.

B.c lymphocytes are so specific only a small number of lymphocytes exist to deal with a particular substance.

33
Q

Describe the anatomy of a lymph node;

A 
Afferent lymphatic vessels
Cortex (b cell region) (b cells form follicles)
Paracortex (T cell region)
Medulla
Efferent Lymphatic Vessel

Antigen is distributed to B and T cell areas

34
Q

Describe the anatomy of the spleen;

A

NO afferent lymphatics as spleen acts as a filter

Splanic Art
Trabeculae
Arteriole

B cell follicles
T cells
DC take pathogens from the blood and present them

Splenic vein

MEDSCI 314 (17 decks)

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