IMMUNITY HMIM BLOCK 224 Dr. ShaikhMujeeb Ahmed Assistant Professor AlMaarefa College
Objectives • General overview of the immune system • Different components of innate & acquired immunity. • Phases of immune response.
What is Immunity ? Immunity is the body’s ability to resist or eliminate potentially harmful foreign materials or abnormal cells.
What are the types of immunity • Innate (natural) immunity • Acquired (adaptive) immunity
What is meant by innate immunity ? • Nonspecific responses • Inherent (innate or built-in) defense mechanisms • Nonselective defend against foreign or abnormal material of any type, even on initial exposure to it.
What is it includes? • Barriers • Physical • Chemical • Defensive cells • WBCs • Macrophages • Natural killer cells (NK) • Chemical defenses • Complement system
Barriers • Integumentary system • Mucus membrane & lysozyme
Cells • Langerhans cells • Phagocytes • Natural killer cells • Basophils and mast cells
Chemicals • Interferon: (are named after their ability to "interfere" with viral replication) • Complement system: (helps or “complements” the ability of antibodies and phagocytic cells to clear pathogens from an organism) • Inflammation: (biological response of vascular tissues to harmful stimuli)
Interferon • α, β, and γ interferon • By infected cells • Function by blocking viral reproduction
Innate Immunity Mechanism of Action of Interferon in Preventing Viral Replication
Complement System Series of ~ 20 proteins Activated by microorganisms Will coat the microorganisms Adherence reactions phagocytic cells have receptors for C3 Biological active fragments produce reactive oxygen intermediates Membrane lesions Activate mast cells
Acquired (adaptive) immunity • specific immune responses selectively targeted against a particular foreign material to which the body has already been exposed. • The foreign material may be an antigen or a hapten (is a small molecule that can produce an immune response only when attached to a large carrier such as a protein)
Immune Response Antigen • Antigen – “any substance when introduced into the body stimulates the production of an antibody” • Bacteria, fungus, parasite • Viral particles • Other foreign material • Pathogen – an Antigen which causes disease
Immune Response Antibodies • Antibody– “a Y-shaped protein, found on the surface of B-Cells or free in the blood, that neutralize antigen by binding specifically to it” • Also known as an Immunoglobulin Antigen
Hapten • Not antigenic by itself • When combines with protein it become an antigen
Adaptive immunity • Two types • Active immunity – direct encounter with the antigen. • Passive immunity – without encounter with the antigen • Antibodies transferred from mother to the fetus. • Immunization by injecting antibodies
Active immunity • Cell mediated immunity (T cell immunity) • Antibody mediated (humoral/ B cell) immunity
Origins of B and T lymphocytes After early childhood most new lymphocytes are derived from peripheral lymphocyte colonies rather than from bone marrow
Interactions between T- and B-Cells T- memory Cell T-supressor Pre-T Cell T8-ctotoxic T-Cell T4-helper Bone Marrow Pre-B Cell Plasma Cell B-Cell B- memory Cell IgG IgA IgD IgM IgE
Phases of immune mechanism • Initial phase • Entry of antigen and its contact with the specific receptor on lymphocytic membrane. • Central phase • Cooperation among different subset of lymphocytes that proliferate and differentiate to form T & B lymphocyte + memory cells • Effector phase • Inactivation of antigen by sensitized T & B lymphocytes
References • Human physiology by Lauralee Sherwood, seventh edition • Text book physiology by Guyton &Hall,11th edition • Text book of physiology by Linda .s contanzo, third edition