بسم الله الرحمن الرحيم

An Introduction to Immunology Prof. Dr. Ezzat M Hassan

I- Historical perspective II- Functions of the Immune System

I- Historical Perspectives Smallpox Chinese: protection provided by sniffing the powder made from crusts of smallpox pustules. Egyptians: powder from crusts of smallpox pustules or vesicle fluid applied to skin and the surface scratched - variolation. (Variolation is the process of taking fluid from pustules and scratching the fluid onto skin) Lady Montague: introduced variolation to Europe by having her children protected from smallpox by this process.

I- Historical Perspectives (cont.) Edward Jenner: (1749-1823) Observed that milkmaids who had suffered from cowpox did not contract smallpox. Protected a young boy from smallpox by deliberate immunisation with cowpox and then challenging him with smallpox. The term vaccination (vacca = latin for cow) was introduced to describe the process. In 1980 the WHO declared the world free of smallpox as a result of widespread vaccination programs.

I- Historical Perspectives (cont.) Louis Pasteur: (1822 -1895) Studied attenuation of organisms and their subsequent use for vaccination eg. Chicken cholera and rabies. Sterilisation of milk by pasteurisation. Fermentation of wine due to action of micro-organisms.

I- Historical Perspectives (cont.) Elie Metchnikoff: (1845 - 1916) Observed the phenomenon of phagocytosis in starfish larvae. Extended this observation to humans and described two types of phagocytic cells circulating in the blood, noted that some fixed cells were also capable of phagocytosis. Called all of these cells phagocytes. Proposed a cellular theory of immunity.

I- Historical Perspectives (cont.) Paul Ehrlich: (1854 -1915) In 1900 proposed a theoretical framework to explain the specificity of antigen-antibody reactions. Proposed the ‘side chain theory’ of antibody receptors on cells with which antigens reacted. From work of Ehrlich, Landsteiner and others, a humoral theory of immunity was developed.

I- Historical Perspectives (cont.) Karl Landsteiner: (1868-1943) In 1901 defined the ABO blood group system. Studied the chemical nature of antigens by creating chemically defined antigens. Coined the term hapten. Awarded the Nobel prize in 1930 for discovery of first blood group.

I- Historical Perspectives (cont.) Niels Jerne: (1944) Clonal selection theory (specificity resides in antibodies) Network theories of immune regulation. Macfarlane Burnet: Clonal selection theory (specificity resides in lymphocytes) Tolerance and the ‘forbidden clone’.

I- Historical Perspectives (cont.) Peter Medawar: (1944) Experimental proof for the deletion of self- reactive clones of lymphocytes during early lymphoid maturation resulting in tolerance. Principles of transplantation. Charles Owen: (1945) Tolerance induction in twin calves (chimera).

I- Historical Perspectives (cont.) Astrid Fagraeus: (1948) Demonstrated that the plasma cell is responsible for the production of antibodies. Robert Porter, Gerald Edelman, Alfred Nisonoff: In 1959, defined the structure of the immunoglobulin molecule by using monoclonal gammopathy proteins (myeloma and macroglobulinaemia) and protein digestion techniques.

I- Historical Perspectives (cont.) Jean Dausset, George Snell: (1944) Identified antigens on leucocytes which determine histocompatability between genetically different individuals. HLA human leucocyte antigens H2 murine (mouse, rat) leucocyte. Paul Terasaki: Microlymphocytotoxicity testing for HLA These three scientists have been awarded Nobel prizes for their discoveries.

I- Historical Perspectives (cont.) Ralph Zinkernagel & Peter Doherty: In 1975 demonstrated the need for self recognition in effector role of cell mediated immunity (CMI). Received the Nobel Prize in 1997 for this work which was carried out in the John Curtin School for Medical Research at the Australian National University in Canberra.

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II-Structure and Functions of the Immune System New Concept of immunity Functions of the immune System

1. New Concept of immunity .Traditional concept: Anti-infection .New concept :The ability of the immune system to recognize and eliminate the antigenic non-self substances and maintain HOMEOSTASIS     .recognize “self” from “non self” . normally beneficial .sometimes injurious

Means protection from disease, especially infectious disease. Immunity: Is derived from the Latin word immunitas which means exemption from civic duties and prosecution. Means protection from disease, especially infectious disease. Cells and molecules involved in such protection constitute the immune system and the response to introduction of a foreign agent is known as the immune response

2. Functions of immune system The chief function of the immune system is to distinguish between self and non-self.

2. Functions of immune system 1)  Immune defense: Protection from harmful environmental antigens. 2) Immune homeostasis: Regulate and maintain the steady state of organisms. 3) Immune surveillance: Search and destroy neoplastic cells.

Health : effective elimination or control of health-threatening agents (Hyporeactivity) (Hyperreactivity) Immunodeficiency Health Immunopathology /\ Control of infectious agents and tumors is required for healthy life.

(Hyporeactivity) Health Immunopathology Hypo-reactivity (immunodeficiency): inability to recognize and control health-threatening agents (Hyperreactivity) (Hyporeactivity) Health Immunopathology Immunodeficiency /\ Neutrophil Disorders Antibody Deficiency Complement Deficiency T & B Cells Dysfunction

Immunodeficiency Health (Hyperreactivity) Hyper-reactivity : aberrant (exaggerated) immune responses (Hyporeactivity) Immunodeficiency Health (Hyperreactivity) Immunopathology /\ Systemic Autoimmunity Organ-Specific Autoimmunity Allergies and Asthma Immunopathology

The immune system consists of two overlapping compartments: 1-the innate (inborn) immune system and 2-the adaptive (acquired) immune system.

Nomenclature of Immune Cells and their locations

Next Lecture : 1- Cells and Organs of the immune system 2- Innate Immunity