3rd immune cells (1)

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Immunology Lecture 3rd

Cells of Immune System

BY

Dr. Humera Kausar

March 2015



Cells of the Immune System



ImmuneCells

Myeloidcells

Granulocytic

Neutrophils

Basophils

Eosinophils

Monocytic

Macrophages

Kupffer cells

Dendritic cells

Lymphoidcells

T cells

Helper cells

Suppressor cells

Cytotoxic cells

B cells

Plasmacells

NK cells


Leucocytes



Cells of the innate immune system:

• Phagocytes

– Monocytes/macrophages

–

Neutrophils/PMNs/• NK cells

• Basophils and mast cells

• Eosinophils



Phagocytic Cells MononuclearPROMONOCYTES

MONOCYTES MACROPHAGES (Fixed or Free)

Brain ---------Microglial cells

Lungs ------------Alveolar cells

Liver ----------------- Kupffer cells

Connective tisues-----HistocytesKidney ---------------------Mesangial cells

Bones ------------------------ Osteoclasts

Skin ------------------------Langerhans cells



Macrophages

• Characteristic nucleus

• lysosomes

• CD14 membranemarker protein

Macrophage



Macrophages

Activated by variety of stimuli in the course of an

immune response. Activated macrophages are more effective then

resting ones in eliminating potential pathogen.

Activated macrophages secreted various cytotoxicproteins that help to eliminate broad range of targets

including

o virus infected cells

o Tumor cells

o Intracellular bacteria

Also act as antigen presenting cells



Macrophage as an antigen presenting cells



Granulocytes

Neutrophils

Polymorphonuclear (PMN) leukocyte.

Has multilobed nucleus and granulated cytoplasm.

Stains with both acidic and basic dyes.

Constitute 50% to 70% of the circulating

leukocytes.

After release in to the blood, circulates 7 – 10 hours

before migrating in to the tissues.

Life span is few days. (3 days)



Neutrophils (PMNs)

•

CD66 membranemarker protein

Geimsa stains

Neutrophil



Neutrophils

First cells to arrive at the site of inflammation.

In response to many types of infections the bonemarrow releases increased number of circulating

neutrophils called leukocytosis.

Act as phagocytic cells.

GRANULOCYTES



Neutrophils GRANULOCYTES

Lytic enzymes and bactericidal substances in

neutrophils are contained within primary andsecondary granules.

Larger denser primary granules are a type of

lysosome containingperoxidase, lysozyme, various hydrolytic enzymes

Smaller secondary granules contains,

collagenases, lactoferr in, lysozyme

Both primary and secondary granules fuse with

phagosomes.



Neutrophil



Eosinophils

Stain with acid dye eosin red.

Has bilobed nucleus and granulated cytoplasm.

Constitute 1% to 3% of WBC population.

Like neutrophils, motile phagocytic cells that can

migrate from blood into tissues.

Phagocytic role of eosinophils are less significant

than that of neutrophils.

Play a role in the defense against parasitic

organisms by secreting contents of eosinophilic

granules, which damage the parasite membrane.

GRANULOCYTES



Eosinophil



Basophils Basophil has a lobed nucleus and heavily granulated

cytoplasm.

Stains with basic dye methylene blue.

Non phagosytic granulocyte.

Constitute <1% of circulating WBC.

Function by releasing pharmacological active

substances from cytoplasmic granules.

Play a major role in certain allergic responses.

GRANULOCYTES



Basophil



Mast Cells

By hematopoiesis, released into the blood as

undifferentiated cells.

Do not differentiate until they leave the blood and

enter the tissues, including

skin, connecting tissue of var ious organs,mucosal epithel ial tissues of respiratory,

genitour inary & digestive tracts

Like circulating basophils, mast cells have large

numbers of cytoplasmic granules that contains

histamines and other pharmacological active

substances.

Play an important role in the development of allergies.



MEDIATORS RELEASED

Prostaglandin D2 Platelet Activating Factor

Tryptase

Heparin Histamin

IL-4, IL-5, IL-6, IL-8

TNF



CAUSING Vasodilation,

increased vasopermeability,

contraction of smooth muscles, bronchoconstriction,

increased eosinophil, neutrophil & monocyte

chemotaxis,

anticoagulation,

increased fibroblast proliferation,

platelet activation



Dendritic Cells

Activation of T cells and

initiate adaptive immunity

Found mainly in lymphoidtissue

Function as antigen

presenting cells (APC)

Most potent stimulator of

T-cell response



Dendritic Cells



Dendritic Cells

DC covered with long membranous extensions

that resemble the dendrites of nerve cells.

Display class I & class II MHC.

B and T lymphocytes are the mediators ofimmunity, but their function is under the

control of dendritic cells.

Dendritic cells in the periphery capture and

process antigens.



Dendritic Cells

Express lymphocyte co-stimulatory molecules,

(B7, CD40)

Migrate to lymphoid organs and secrete

cytokines to initiate immune responses. They not only activate lymphocytes, they also

tolerize T cells to antigens that are innate to the

body (self-antigens), thereby minimizingautoimmune reactions.



Dendritic cells initiate antigen-

specific immune responses

• most efficient of all APCs

• high MHC class I, II & costimulators

•

efficient cross presentation• stimulate naïve T cells (CD4, CD8)

initiate Ag-specific immune responses

All immunization strategies must target DCs



Immature:

antigen

capture

Mature:

antigen

presentation



Cells of the immune system:

APC• Cells that link the innate and adaptive arms

– Antigen presenting cells (APCs)

• Heterogenous population with role in innate immunityand activation of Th cells

• Rich in MHC class II molecules

– Examples

• Dendritic cells

• Macrophages

• B cells

• Others (Mast cells)



Cells of Adaptive Immune

System

T cells and B cells



Cells of the Adaptive Immune System:

• Lymphocytes (Lymphoid Cells)

– B cells

• Plasma cells (Ab producing)

• Memory cells

– T cells

• Cytotoxic (CTL)

• Helper (Th)

– Th1

– Th2

– Null cells (NK cells)



Lymphoid Cells

Contributes 20-40% of body’s WBCs, Naïve or unprimed cells are small, motile, non-

phagocytic cells.

Can not be distinguished morphologically. Resting cells are in G0 phase of cell cycle.

Small lymphocytes are 6 um in diameter.

Cytoplasm barely covers the rim aroundnucleus.



Lymphoid Cells

Have,

o densely packed chromatin

o

few mitochondriao poorly developed endoplasmic reticulum

o Golgi apparatus

Life span of effector cell is few days to few

weeks.

B L h



B-Lymphocytes

Derived its name from its site of maturation in the

Bursa of fabricius in birds and Bone marrow in humans

• Plasma cells (Ab producing)

• Memory cells



B-CELL RRECEPTORS

Membrane bond Ig molecules

i.e.,1.5 x 105 molecules/cell

CD 45 (Marker B220) MHC II (Antigen Presenting

receptor)

CD35 (Complement receptor) CD21 (Complement receptor)

CD32 (Fc RII)



T-CELL RRECEPTORS

TCR

Thy 1 (1st receptor remainsthroughout life span of the cell)

CD4 (T- helper cell)

CD8 (T- cytotoxic cell)

Ratio of Th : Tc = 2:1



Specificity of adaptive immune

response

• Resides with Ag

Receptor on T and B

cells

•TCR and BCR

– both

specific for only ONE

antigenic determinant

• TCR is monovalent

• BCR is divalent

T cellTCR Ag

B cellBCR



T-Lymphocytes

T- helper cell vs T cytotoxic cell)



T helper cells and (TH) Class II MHC proteins

Specialized TH cell involved in

the inflammatory response

Cell-cell interaction mediated

by the TCR and the class II

MHC-antigen complex activates

The TH cell which produces

cytokinesTNF-alpha (tumor necrosis factor)

IFN-gamma (interferon)

GM-CSF (granulocyte-monocyte

colony stimulating factor)

These cytokines further stimulate

macrophages to increase phagocytic

activity and to in turn produce cytokines

that promote inflammation



Cytotoxic T cells (Tc) and Class I MHC proteins

The cell-cell interaction betweenthe infected cell and the Tc

cell is mediated by the

MHC/antigen complex and TCR

The Tc cell produces cytotoxic proteins

perforins — produce holes or pores in the

target cell and granzymes enter the

virus infected cell causing apoptosis or

programmed cell death

The cytotoxic proteins only affect those

cells to which the Tc cell has specifically

interacted



NATURAL-KILLER CELLS

A A C S



NATURAL-KILLER CELLS

Fails to express membrane molecules that

distinguished B and T cells.

Fails to express antigen binding receptors.

Constitute 5% - 10% of lymphocytes in humanperipheral blood.

NK cells have ability to recognize tumor or

virus infected cells.

NK cells express membrane receptor CD16 for

a specific region of antibody molecule (ADCC).



Human red blood cells

(red), activated platelets

(purple) and white blood

cells - monocyte (green)

and T lymphocyte

(orange).

Colorized-SEM

(scanning electron

micrograph)

Magnification:-1200x--(Based on an image

size of 1 inch in the

narrow dimension)




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3rd immune cells (1)

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