INTRODUCTION TO IMMUNITY IMMUNOLOGY LECTURE 1 Dr Jayne Powles

By the end of this lecture you should.. Understand what immunity is Know the components of & the role of the immune system Be able to name each of the WBC, know their roles & know how to identify them Know the roles of the lymphoid organs/tissues Have been introduced to the main forms of defence the body employs…

Disease –Damage or injury that impairs normal physiological function. –Invasion by micro-organism, by parasite, by poison, by cancer, hereditary / genetic cause, by diet, etc. Infection –Where micro-organism is established & growing in host –Doesn’t always cause disease / host damage

Immunity If immune to a disease –Does NOT mean cannot contract it –More readily able to fight it as body has been previously exposed to infection or vaccination Unwell –May have contracted a virus, bacteria, etc. that body is fighting but due to “immunity” - symptoms not severe

Immunity Immunity – recognition & removal of non-self (antigen) from self (body) Immune system –Fights disease –Consists of organs, cells & molecules CELLS – white blood cells, some blood components ORGANS – thymus, lymph nodes, spleen, lymphoid tissues

Blood Cellular & extra-cellular (plasma) –Plasma 90% water Proteins - albumin, antibodies, fibrinogen, complement proteins –Red blood cells (erythrocytes) –White blood cells (leukocytes)-many types –Platelets

Leukocytes (WBC) Lymphocytes - recognise and respond to foreign antigens –Contain a large round nucleus that stains with hematoxylin. –Source = bone marrow Lymphoid stem cells –Can replicate Three types: Natural Killer Cells - innate immunity T cells – acquired immunity B cells – produce antibody

Antigen/Antibody Reactions Antigen (Ag) = Non-self –eg.microbe, parasite, foreign body, abnormal cell Antibody (Ab) = Protein –specifically designed to “fit” onto specific Ags & so neutralise them Ag-Ab complex : –Making Ag ineffective, disrupts Ag surface / functions –Attracting more immunity components to help destroy Ag –Exploited to make vaccinations & antiserums

Specific binding

Monocytes – phagocytic (“eating of microbes”) Source = bone marrow Myeloid stem cells Enter tissues few hours after release into general circulation Develop into wandering & fixed macrophages Long life Can multiply Insert picture of monocyte here Leukocytes (WBC)

Granular (cytoplasm filled with granules) Neutrophils Granules do not take up stain Enter tissues few hours after release into general circulation Mature & immature Life expectancy is few days Cannot replicate Phagocytic role Insert picture of neutrophil here

Leukocytes (WBC) Eosinophils Take up acid dyes such as eosin Circulate blood stream 30 mins than enter tissues Involved in allergic responses (Type 1 hypersensitivity) Release molecules that contribute to inflammation Basophils Take up basic dyes such as haematoxylin Generally found in blood stream Contain vasoactive molecules - makes smooth muscle contract in allergic responses Insert picture of eosinophil here Insert picture of basophil here

Primary Lymphoid Organs Provide a site for lymphocytes to develop and mature from a lymphoid stem cell. Thymus T lymphocytes develop in the thymus –Thymus degenerates with age as T-cells can divide so once mature & body has enough, loses its role.

Primary Lymphoid Organs B cells - develop in different organs depending on species, eg. Bone marrow – primates and rodents Intestinal lymphoid tissues (Peyer’spatches) - rabbits, ruminants, pigs Bursa of Fabricius - birds

Secondary Lymphoid Organs Sites where lymphocytes are most active. Help trap antigens for lyphocytes to act on. Enlarge in response to antigenic stimulation. Examples: Spleen Lymph nodes Tonsils Lymphoid tissues (intestinal, respiratory and urogenital tracts)

Immune System Body has 2 main ways of defending itself : –Innate immunity – non-specific, involves barriers, neutrophils & macrophages –Adaptive immunity – highly specific, involves lymphocytes Inflammation –Defence mechanism –Reaction of vascularised living tissue to local injury –White blood cells involved