INTRODUCTION TO IMMUNOLOGY CLS 245

The eradication of smallpox was a major success of immunotherapy.

IMMUNOLOGY AND THE IMMUNE SYSTEM Immunology – Study of the components and function of the immune system Immune System – Molecules, cells, tissues and organs which provide non- specific and specific protection against Microorganisms Microbial toxins Tumor cells – Immune system is crucial to human survival

Organs of the Immune System

Levels of defense against pathogens

Body lines of defences 1.First line of defence – non-specific barriers 2.Second line of defence – innate immunity 3.Third line of defence – adaptive immunity

First line of defence – non-specific barriers These are a combination of physical and chemical barriers that prevent all types of foreign agents from penetrating the outer layer of the body. No specific foreign agent is targeted at this level. The barriers are: The skin – excellent barrier to pathogens. Mucous membranes – line the entrances to the body such as in the respiratory tract entrances. Mucus produced by these membranes traps foreign particles and directs them out of the body. Hair – (nasal hair) trap dust and dirt. Gastric juice, vaginal secretions and urine – acidic fluids that have a protective function. Tears, sweat and saliva – body fluids which possess some anti-bacterial properties. Cerumen (ear wax) – produced in the ear canal and protects the canal by trapping dirt and dust particles.

Figure illustriting non-specific barriers in human

Definitions: Antigen (Ag) – Foreign substance that, when introduced into the body, is capable of stimulating an immune response Antibody (Ab) / also called immunoglobulin (Ig) – A protective protein produced by the immune system in response to the presence of a foreign substance, called an antigen – There are 5 types of anibody (IgM, IgA, IgG, IgE, IgD) Antibiotics – Antibiotics are powerful medicines that fight bacterial infections – Overuse of antibiotics can weaken the efficiency of the immune system

Immune response to infection involves: 1- RECOGNITION – locate and identify the pathogen 2- DEFENSE – repel and destroy the pathogen

THE IMMUNE RESPONSE AND IMMUNITY Immune response – Innate (non-specific) – Adaptive (specific) Immunity – State of non-specific and specific protection Acquisition of Immunity – Natural Examples: 1- Antibodies in the breast milk of mothers. 2- Overcome an infection ex. Chicken pox – Artificial Example: vaccination

DEFENSE MECHANISMS OF THE HUMAN HOST Innate Mechanisms (Innate immunity) – Second line of defense – Non-specific Adaptive Mechanisms (Adaptive immunity) – Third line of defense – Highly specific with memory Cooperation between mechanisms

WHAT ARE STEM CELLS?

Stem cells have the remarkable potential to develop into many different cell types in the body during early life and growth.

Innate Immune Response at sites of Infection

Examples of Cells participate in innate immunity 1.Phagocytes o Macrophage (MΦ) o Neutrophil 2. Natural killer cell (NK Cell) 3. Mast cell

Adaptive immunity Adaptive immunity refers to antigen-specific immune response. The adaptive immune response is more complex than the innate. The antigen first must be processed and recognized. Once an antigen has been recognized, the adaptive immune system creates an army of immune cells specifically designed to attack that antigen. Adaptive immunity also includes a "memory" that makes future responses against a specific antigen more efficient.

CONTINUE antigen-presenting cell (APC) like Dendritic cells and some Macrophages play the role of linking between the innate and adaptive immune systems

Cells of the adaptive immune system Cells that make up the adaptive (specific) immune system include the B and T lymphocytes. After exposure to antigen, B cells differentiate into plasma cells whose primary function is the production of antibodies. Similarly, T cells can differentiate into either T cytotoxic (Tc) or T helper (Th) cells

PRIMARY AND SECONDARY ANTIBODY RESPONSE Primary Response – Following exposure to an antigen, there is a slow rise in IgM followed by a slow rise in IgG Secondary Response – Following exposure to previously encountered antigen, there is a rapid rise in IgG and slow or no rise in IgM Memory or anamnestic response

Innate immunity Adaptive immunity

DISORDERS OF THE IMMUNE SYSTEM Hypersensitivity Reactions – Over-reaction of adaptive immune response to harmless antigens – Four Types of reactions (I,II,III and IV) Autoimmunity – Misdirected adaptive immune response – Results from a loss of self-tolerance – Three Types (II, III, IV) of reactions Immunodeficiencies – Components of immune system either absent or defective (example: acquired immune deficiency syndrome AIDS) – Genetic or acquired etiology