Cells and tissues of the immune system Lisbeth N. Fink Nutritional Immunology Group – CBS - DTU

Protecting borders to the outside world Challenges 1) Discrimination between self and non-self –bacteria –fungi –vira –parasites –(transplants) 2) Evolution 3) Dealing with non-pathogenic factors

First lines of defense Anatomical Skin Mucosae Ciliae Physiological Temperature 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 cells B cells Antibodies Memory MHC - HLA Diversity Somatic hypermutation Polymorphism Granulocytes Monocytes Macrophages Dendritic cells NK cells NK T cells Complement Pattern recognition Adaptive/SpecificInnate/Non-specific

Characteristics of the two parts T cells B cells APC Antibodies Memory MHC - HLA Diversity Somatic hypermutation Polymorphism Granulocytes APC Monocytes APC Macrophages APC Dendritic cells APC NK cells NK T cells Complement Pattern recognition Adaptive/SpecificInnate/Non-specific

Antigen uptake - phagocytosis Phagocytic cells: Granulocytes Monocytes Macrophages Dendritic cells

Antigen uptake Preference for ”opsonized” bacteria

MHC I and II TcTc THTH

T cells Helps: B-cells T cells Macrophages Kills: Infected cells Tumour 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