The Immune System Donna Howell Medical Microbiology Blacksburg High School Unit 13

Overview of Immune System Our immune systems consist of two main types of resistance: 1.Non-specific – body ’ s defense against ANY type of pathogen 2.Specific – body ’ s defense against a SPECIFIC pathogen

The Immune System Lymph nodes: Lymph nodes contain billions of white cells, multiplying rapidly to fight the invading germs. During illness they fill with millions of extra white cells and also dead germs. Bone marrow: Produces all white blood cells. Spleen: An immunologic filter of the blood, the spleen is made up of red and white blood cells. Adenoids: The adenoids are found in the top and back of the throat and help guard against illness by identifying harmful bacteria, fungi, and viruses in food or the air. White blood cells in the adenoids incapacitate the invading germs and help produce antibodies to fight future infections.

Non-Specific Resistance First line of defense: Intact skinIntact skin Mucous membranes & secretionsMucous membranes & secretions Normal flora on bodyNormal flora on body

Non-Specific Resistance Second line of defense: Phagocytic white blood cellsPhagocytic white blood cells Inflammation and feverInflammation and fever Antimicrobial substancesAntimicrobial substances

Specific Resistance Third line of defense: Specialized white blood cellsSpecialized white blood cells AntibodiesAntibodies

Skin & Mucous Membranes Mechanical factors – intact skin, tears, cilia in throat, epiglottis, urine, vaginal secretionsMechanical factors – intact skin, tears, cilia in throat, epiglottis, urine, vaginal secretions Chemical factors – sebum, perspiration, gastric juice, vaginal secretions.Chemical factors – sebum, perspiration, gastric juice, vaginal secretions. Normal flora – normal bacteria act as a barrier to other microbes trying to enter by competing for nutrients and producing toxic substances.Normal flora – normal bacteria act as a barrier to other microbes trying to enter by competing for nutrients and producing toxic substances.

Blood Components There are two main components of our blood: 1.Liquid part – called plasma 2.Cells – 3 types: 1.Red blood cells 2.White blood cells 3.Platelets

Red Blood Cells The purpose of red blood cells is to carry oxygen to our tissues.

Platelets Platelets aid in the clotting of our blood when we are hurt. Platelets

White Blood Cells White blood cells, or leukocytes, are the cells that are part of our immune system. They are the phagocytic cells. This is what pus is made out of. There are 5 main types, and will each be discussed on the next 5 slides.

Neutrophils The purpose of neutrophils is strictly phagocytosis of bacteria, viruses and fungi. Comprise 60-70% of our wbc ’ s.

Basophils Basophils migrate to damaged tissues and release histamine to promote inflammation and heparin to inhibit blood clotting. Make up <1% of our wbc ’ s.

Eosinophils Eosinophils moderate allergic reactions as well as defend against parasitic infections. Make up 2-4% of our wbc ’ s.

Monocytes Monocytes are also phagocytic cells. They comprise 3-8% of our wbc ’ s.

Lymphocytes Lymphocytes are the major players in specific immune reactions, and some produce antibodies. Comprise 20-25% of our wbc ’ s.

Phagocytosis This is the ingestion of a microorganism by white blood cells. 4 stages: 1.Chemotaxis – chemical attraction of wbc to organism 2.Adherence – attachment of wbc to surface of organism 3.Ingestion – pseudopods engulf the organism 4.Digestion – digestive enzymes digest organism

Phagocytosis – The Process

Inflammation Damage to the body ’ s tissues triggers a defensive response called inflammation. 4 signs and symptoms: 1.Redness 2.Pain 3.Heat 4.Swelling

Inflammation The purpose of inflammation is to destroy the invading pathogen, or to limit the effects on the body by confining or walling off the pathogen and it ’ s by- products.

Inflammation 3 stages of inflammation: 1.Vasodilation – blood vessels dilate and become permeable, thus allowing white blood cells to move out of blood stream and into tissue 2.Phagocytosis – white blood cells engulf the pathogen and die, forming pus 3.Tissue repair – body replaces dead and damaged cells Pus Smear

Process of Inflammation

Fever This is the body ’ s response to any injury. High temperatures serve to speed up the body ’ s reactions, thus allowing it to heal quicker.

Antimicrobial Substances The body also produces two main antimicrobial substances: 1.Complement – proteins in blood that participate in the lysis of foreign cells, in inflammation, and in phagocytosis. 2.Interferons – these are antiviral proteins that interfere with viral reproduction

The Immune Response Immunity is a SPECIFIC defensive response by our bodies. Also called acquired immunity because we only acquire it when our bodies encounter a specific pathogen.

Acquired Immunity There are two types of acquired immunity: 1.Naturally acquired – happen through natural exposure to pathogens 2.Artificially acquired – we deliberately expose our bodies to a pathogen, thus stimulating the immune response

Naturally-Acquired Immunity There are two types of naturally-acquired immunity: 1.Active immunity – this is what happens when we are randomly exposed to pathogens. 2.Passive immunity – this is when a mother transfers her antibodies to her fetus across the placenta

Artificially-Acquired Immunity There are two types of artificially-acquired immunity: 1.Active immunity – the type of immunity that is stimulated by vaccination. 2.Passive immunity – when antibodies are produced elsewhere, and injected into a body

Antibodies Antibodies are proteins that are made by the body in response to a specific pathogen. Different pathogens cause our bodies to produce different antibodies. Once antibodies are produced, they remain in our bodies for a long time, so that if we encounter the same pathogen again, we are protected.

Question??? If antibodies remain in our bodies for a long time, how come we get the common cold over and over? Why aren ’ t the antibodies protecting us when we get it again?

Antigens An antigen is any substance that is foreign that gets into our bodies and stimulates our immune system. Ex: bacteria, viruses, pollen, dust, etc.

Immune System Duality The immune system consists of two major mechanisms: 1.Humoral Immunity – involves B cells (wbc ’ s) which produce antibodies against free- floating pathogens 2.Cell-Mediated Immunity – involves T cells (wbc ’ s) that kill intracellular pathogens by phagocytosis

Immune System Duality

Immunization Immunization is to make immune by vaccination. 1.Herd immunity – when a person is not vaccinated, but is protected because everyone around them IS vaccinated. 2.See list of vaccine-preventable diseases in your notes.

Vaccination Schedules

Always remember…

The End! All this talk of blood has made me very thirsty……..