Dr. Shaikh Mujeeb Ahmed Assistant Professor AlMaarefa College IMMUNITY HMIM BLOCK 224 Dr. Shaikh Mujeeb 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 Defensive cells Chemical defenses 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 Inactivated---specific inhibitory proteins if complement doesn’t bind quickly then ecome inactivated

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

T and B Lymphocytes

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 T-Cell T8-ctotoxic T4-helper Bone Marrow Pre-B Cell B-Cell Plasma Cell B- memory Cell IgG IgA IgM IgD 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