Chapter 2 Concept, Functions and Types of Immunity

Introduction  Concept and functions of Immunity  Types of Immunity Chapter 2 Concept, Functions and Types of Immunity

Part I Concept and functions of Immunity

I Concept of Immunity 1)Tranditional concept----Immunity refers to protection against infectious diseases. 2)Modern concept---- Immunity is a function of which an individual recognizes and excludes antigenic foreign substances. It is normally beneficial,but sometimes,it is injurious.

II Concept of Immunology 1) Tranditional concept----anti-infection immunity to different types of pathogenic microorganisms. 2) Modern concept----Immunology is an independent subject about composition,functions of immune system; mechanism of immune response and the disease associated with immunity.

III Functions of Immunity  Immune defense  Immune homeostasis  Immune surveillance

Functions and Manifestation of Immunity Functions Normal Manifestation Abnormal Manifestation Immune Anti-infection Hypersensitivity Defense Immunodeficiency Immune Eliminate injured and senile cells immune dismodulation Homeostasis Tolerate to self components Autoimmune disease Immune destroy transformed cells Tumor or Surveillance (anti-tumor ) Persistent virus infection Prevent from persistent infection

Part II Types of Immunity I. Innate Immunity (or native immunity/ non-specific immunity /congenital immunity) II. Adaptive Immunity (or acquired immunity/specific immunity)

I. Innate immunity ( natural immunity/ non-specific immunity ) Innate immunity: Protection against infection that relies on mechanisms that exist before infection,are capable of a rapid response to microbes,and react in essentially the same way to repeated infections.  Exists at birth  Be the first line of defense against infection

1. Characteristics  Exists naturally  Non – specific  No immune memory (innate immunity can ’ t be enhanced by the second stimulation of the same antigen) Immune memory: Exposure of the immune system to a foreign antigen enhances its ability to respond again to that antigen.  Hereditable  No racial difference Innate immunity

2. Composition (1) Barriers  Physical barrier : skin and mucosa  Chemical barrier: antimicrobial substances in secretion of skin and mucosa  Biotic barrier: normal flora existing on the surface of skin and mucosa  Anatomic barrier. blood- brain barrier. blood- placental barrier. blood- tymus barrier

(2) Humoral factors  Complement  Lysozyme  Interferons(IFN)  C-reactive protein

(3)Cells participating in innate immunity  Phagocyte: endocytosis and phagocytosis mononuclear phagocytes ----Monocytes,Macrophages (M Φ)----PRR Neutrophils  Nature killer cells (NK) — KAR/KIR,IgG Fc receptor  Dentritic cells(DC)  γδ T cells  B1 cells  Other cells participating in innate immunity

NK cells Macrophages Neutrophils

Macrophages

Macrophages excluding the pathogen

II.Adaptive immunity ( acquired immunity/specific immunity) Adaptive immunity: The form of immunity that is mediated by T or B lymphocytes and stimulated by exposure to infectious agents.  Take effects after innate immune response  Be the second line of defense against infection

1.Characteristics  Specificity  Acquired (set up after birth )  Immune memory (Adaptive immunity can be enhanced by the second stimulation of the same antigen)  Transferable  Self-limitation

2.Composition  T cell : Cell-mediated immunity (CMI)  B cell : Humoral immunity(HI) or antibody-mediated immunity

3.The process of immune response in adaptive immunity  Recognition of antigens  Activation,proliferation and differenciation of T or B lymphocytes  Effector phase of immune response ----Elimination of antigens

Comparison of Adaptive and Innate Immunity Innate immunity Adaptive immunity Characteristics Exists naturally Acquired by antigen stimulation after birth Responds rapidly in the early develops slowly stage of infection No antigen specificity Has antigen specificity No immune memory Has immune memory Participates in natural defence Participates in specific immune response Cells Neutrophil,Phagocytes,NK cell et al. T cell, B cell, APC Molecules Complement.lysozyme,cytokines et al Antibody,cytokines