Cells and tissues of the immune system

Lisbeth N. FinkNutritional Immunology Group – CBS - DTU

Protecting borders to the outside world

Challenges1) Discrimination between self and non-self

– bacteria– fungi– vira– parasites– (transplants)

2) Evolution

3) Dealing with non-pathogenic factors

First lines of defense

An

ato

mica

l

Skin

Mucosae

Ciliae

Physio

logica

lTemperature

pH

Lysozyme

Lymphoid organs and lymphatics

Second line of defense: Humoral factors

Humor = liquid (From greek, 4 humors controlling health and mood: blood, phlegm, yellow and black bile)

Antibodies – specific pathogen recognition

Complement system – non-specific recognition

Reactive oxygen species (ROS) – bactericidal activity

Inflammation – recruitment of cells

Third line of defense: Immune cells

Haematopoieisis

Adaptive/SpecificInnate/Non-specific

Leukocytes/White blood cells

Red blood cells

Lymphocytes

Characteristics of the two parts

T cellsB cells

AntibodiesMemory

MHC - HLADiversitySomatic

hypermutationPolymorphism

Granulocytes Monocytes

MacrophagesDendritic cells

NK cellsNK T cells

ComplementPattern recognition

Adaptive/Specific Innate/Non-specific

Characteristics of the two parts

T cellsB cells APCAntibodiesMemory

MHC - HLADiversitySomatic

hypermutationPolymorphism

Granulocytes APCMonocytes APC

Macrophages APCDendritic cells APC

NK cellsNK T cells

ComplementPattern recognition

Adaptive/Specific Innate/Non-specific

Antigen uptake - phagocytosis

Phagocytic cells:

GranulocytesMonocytes MacrophagesDendritic cells

Antigen uptake

Preference for ”opsonized” bacteria

MHC I and II

Tc TH

T cells

Helps:B-cellsT cells

Macrophages

Kills:Infected cellsTumour cells

Recognizes MHC II on APC

Recognizes MHC I on all cells

T cell receptor

Antigen presentation

3. Signal

Cytokines ↔ Cytokine receptors

Activation + Proliferation + Help or Killing

B cells – plasma cells

T cell help for B cell activation

B cells – memory cells

Meeting places (B – T – APC)

What about ’endogenous’ challenges?

Cancer cells – tumor antigens

Immune reactions within self-tissues: autoimmunity

Discontinuation of immune responses

…and reactions to harmless environmental factors: allergy (to food, pollen, fur etc.)

Immunity vs. Tolerance