IMMUNITY CELL MEDIATED IMMUNITY Dr Ahrsia V F

IMMUNITY CELL MEDIATED IMMUNITY Dr. Ahrsia V F Department of Physiology 21/9/18

Contents • Definition and classification of Immunity. • Mechanisms of innate immunity • Development of cellular immunity.

DEFINITION • Immunity is defined as the ability to resist pathogens and their toxic products that tend to damage the tissue or organs.

CLASSIFICATION • Non specific immunity/ Innate immunity. • Specific immunity / acquired immunity. Active immunity Natural Artificial Passive immunity Natural Artificial

ACTIVE IMMUNITY • Acquired by synthesis of antibodies and production of immuno-competent cells by individuals own immune system in response to antigenic stimulus. • Natural- clinical/ subclinical infections. • Artificial- vaccines

PASSIVE IMMUNITY • Immunity is transfered in an ready made form. • Natural- mother to fetus. • Artificial- injecting ready made antibodies.

DIFFERENCES BETWEEN ACTIVE AND PASSIVE IMMUNITY Active immunity Passive immunity • Produced by body’s own immune system. • Latent period varying from few days to weeks. • Immunological memory is present. • Long lasting. • More effective and confers better protection. • Not useful in immunodeficient individuals. • Administration of antibodies into the host. • No latent period. • No immunological memory. • Lasts for short duration. • Less effective. • Useful in immuno-deficient hosts.

INNATE IMMUNITY

MECHANISMS OF INNATE IMMUNITY. Mechanical defence. Chemical defence. Defence by NK cells. Defence by phagocytic cells. • Defence through inflammation and fever. • •

ANTIGEN Any foreign molecule that can trigger a specific immune response against itself or cell bearing it. Properties of antigen: • Immunogenicity. • Reactivity. • Complete antigen. • Hapten- lacks immunogenicity. Epitope/ antigenic determinant

Major histocompatibility complex (MHC antigen) Human leucocyte associated antigens (HLA antigen) • MHC I antigen • MHC II antigen Significance: • Histocompatability • Immunity • Paternity test

DEVELOPMENT OF CELL MEDIIATED IMMUNITY

Origin and development of T cell • Pluripotent stem cells • Thymus gland • Lymphocytes

CELLULAR IMMUNITY T cells • Cytotoxic T cells/ CD 8 cells. • Helper T cells/ CD 4 cells. . • Suppressor T cells. • Memory T cells. Mechanism of cell mediated immunity. • Antigen recognition, processing and presentation. • Activation and proliferation of T cells. • Degradation of intruder

PRESENTATION TO CYTOTOXIC T CELLS Vander, Human Physiology, The Mechanisms of Body Function, 7 e (1998)

ANTIGEN RECOGNITION, PROCESSING AND PRESENTATION • Antigen presenting cells (APCs) Antigen appear on plasma membrane complexed with MHC Protein of host cell. • Macrophage, B lymphocytes, dendritic cells.

LYMPHOKINES • Interleukin 2, 3, 4, 5, 6. • Granulocyte- monocyte colony stimulating factor. • Interferon-ɣ.

Proliferation & Differentiation of T cells • Stimulation of growth and proliferation of cytotoxic T cells, Memory T cells and suppressor T cells. Mainly by IL-2, and less potent actions by IL-4 and 5. • Stimulation of growth of B cell and differentiation to form plasma cells and antibodies. IL-4, 5, 6 – also called as B-cell growth factors. • Positive feedback effect on Helper T cells.

Vander, Human Physiology, The Mechanisms of Body Function, 7 e (1998)

Elimination of intruder

Suppressor T cells • Regulatory T cell. • Suppresses the functions of cytotoxic and helper T cells. Helper T cell ++ Suppressor T cell Cytotoxic T cell

Memory T cell

Thank you