Cells In Immunology

Question 1

Role of the immune system

Answer 1

-Role of immune system is to protect the body from damage caused by microorganisms.

-This is achieved by white blood cells (AKA Leukocytes) and various accessory cells found throughout the body particularly in the lymphoid organs

Question 2

Lymphoid organs

Answer 2

-Lymphoid organs include BONE MARROW, THYMUS, SPLEEN, and mucosa-associated lymphoid tissue
-Lymphoid organs are strategically placed to protect different areas of the body from infection
-Cells move between the tissues via the bloodstream and lymphatic system. Whilst they do this, they interact with each other to generate coordinated immune responses, in order to eliminate pathogens or minimise the damage they cause.

Question 3

List the different type of immune cells

Answer 3

-lymphocytes
-antigen -presenting cells
-accessory cells

Question 4

Different types of immune cells

Answer 4

-lymphocytes
-antigen -presenting cells
-phagocytes
-accessory cells

Question 5

Lymphocytes

Answer 5

-Important cells controlling the immune response
-Achieve this by recognizing molecules produced by
pathogens
- Can recognise molecules on cells of body, but do not normally react against the body’s own tissues (unless in autoimmune disease)
- Molecules recognized by lymphocytes are called ANTIGENS
- Recognize foreign material by specific cell-surface antigen receptors
- The receptors are extremely diverse so that they can recognize any potential molecule encountered during individual’s lifetime
-Each lymphocyte makes only 1 type of antigen receptor- i.e. they are specific (part of ADAPTIVE IMMUNITY)

Question 6

What are the 3 types of lymphocytes

Answer 6

-B cells/B lymphocytes which produce ANTIBODIES
-T cells/T lymphocytes which have several roles (see below)
-Natural killer cells role in antiviral defense (much less common than B and T cells)

Question 7

Function of T cells

Answer 7

-Helping B cells to produce antibody
-Recognizing and destroying cells that have become infected with intracellular pathogens
-Activating phagocytes to destroy pathogens that they have taken up
- Regulating the level and quality of the immune response

Question 8

Lymphocytes characteristics (b and T cells)

Answer 8

-20-40% in peripheral blood
-round nucleus which is large and produces a dark staining
-scanty cytoplasm which is barely visible,pale eosinophilic,thin rim around the nucleus

Question 9

B cells

Answer 9

-recognise the enemy which is a b cell receptor
-receive signal fro activation:
>show antigen to CD4 T cells (antigen presenting)
>recognise multiple crosslinking(thymus independent activation)
-transform into:
>plasma cells which secrete antibodies
>memory b cells for faster recognition of the same enemy in the future

Question 10

Killer T cells

Answer 10

-expressed cd8 glycoprotein
-killing strategy
>recognise antigen combined with class 1 Mhc
>receive signal for activation:
=with cd4 T cell help:cytokines
=without help:activation by potent APCs
-release cytotoxic proteins
+perforin which forms a pore for delivering of granzymes
+granzymes which programmes cells to die
+granulysin which stabs the cells(creates holes in target membrane and destroys it)

Question 11

List cytotoxic proteins released by killers cells

Answer 11

Perforin
Granzymes
Granulysin

Question 12

T helper cells

Answer 12

-ExpressesCD4 glycoprotein (CD4+ T cells)
-Th1 cells
Activates:
• Macrophages
• Killer T cells
• b cells
Secretes;
IFN-Y
IL-2
TNF-a

-Th2 cells
Activates:
• Eosinophils
• Mast cells
• basoonlis
Secrets;
IL-4
IL-5
IL-13

-Treg cells
+Inhibits dendritic cells
+Prevents autoimmunity
+Suppresses T cell
-Th17 cells
Recruits:
• Neutropnis
Secretes:
• IL-17
-Teh cells
Activates b cells for
• Isotype switching
•affinity maturation

Question 13

Natural killer cells

Answer 13

-expresses cd16 glycoprotein,cd56 glycoprotein
-recognise antigen combined with class 1 mhc
-Signal for activation:IFN-A,AFN-B,IL-12
-release cytotoxic proteins:
+perforin which form a pore for delivery for granzymes
+granzymes:programmes cell to die

Question 14

Phagocytes

Answer 14

-Ingest (PHAGOCYTOSE) pathogens, antigens and cell debris and break them down
- Antibodies and other recognition molecules help in this process
- Phagocytes include blood monocytes, macrophages and neutrophils
- Macrophages can also process and present antigens so that they can be recognized by T cells

Question 15

Phagocytes:neutrophils

Answer 15

-count 40-60% in peripheral blood
-cytoplasmic granules which are neutrally staining and are pink in colour
-multyilobed nucleus’s
-killing strategy is
>chemotaxis
>recognise enemy(igG AND C3b receptors)
>phagocytosis

Question 16

Phagocytes:monocytes

Answer 16

-count 1-6% peripheral blood
-abundant cytoplasm which is pale blue and a granular
-kidney-bean shaped nucleus
-killing strategy
>chemotaxis
>phagocytosis
>transform into larger phagocytise cells,the macrophage

Question 17

Accessory cells

Answer 17

-Accessory cells include granulocytes (eosinophils and basophils), mast cells, platelets and antigen-presenting cells (APCs)
-APCs include B cells, macrophages, dendritic cells* (*most important) in presenting antigen to NAÏVE T cells

Question 18

Accessory cells:esinophils

Answer 18

-1-3% in peripheral blood
-bilobed nucleus which is spectacle shaped
-cytoplasmic granules bright pink in colour,small in size
-killing strategy
>chemotaxis
>recognise target via Fc receptors
>phagocytosis
>chemical attack(release toxic contents of granules)

Question 19

Accessory cells:basophils

Answer 19

-count less than 1% in peripheral blood
-biolbed nucleus which is long band ribbon-like,less distinct indentations
-cytoplasmic granules which are purple in colour
-killing strategy ;
>chemotaxis
>recognise target(cross-linkage of receptor bound igE molecules by antigen
>degranulation(explode)

Question 20

Accessory cells:mast cells

Answer 20

-located in mucosal tissues and connectives tissue
-has two types of nucleus:multi globular,large eccentric
-cytoplasm which is a large granule purple in colour
-killing strategy
>matures in tissues
>recognises target (vrooms-linkage of receptor igE molecules by antigen)
>deregulation

Question 21

Antiugen -presenting cells :dendritic cells

Answer 21

-expresses Hugh Levels of mgc class 2
-long cytoplasmic processes for efficient antigen presentation
-killing strategy
>phagocytosis
>Ingest ECF an contents(macropinocytosis
>Antigen presentation
>Activates them via co-stimulators signals