MBIO 1010 Study Guide - Final Guide: Immunoglobulin G, Thymus, Basophil
31 May 2018
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MBIO 1010 - Summer 2018
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UNIT 5 – IMMUNITY AND HOST DEFENCE
Overview of Immunity
- Immune system can be divided into two major branches
1. Innate (non-specific) immune response
o Exists at birth and always present
o Defends against all invaders equally
o Does not have memory
§ Responds against each invader the same way, every time it is encountered
o Includes physical and chemical barriers, special immune system cells, physiological
processes and molecular defenses.
2. Adaptive (acquired, specific) immune response
o Acts against a specific intruder
o Acquired when a pathogen is encountered for the first time
o Has memory
§ Responds more vigorously the
second time a particular
pathogen is encountered
§ Symptoms are barely felt
o Divided into two branches
§ Humoral (antibody mediated)
immunity
§ Cellular (cell mediated) immunity
Innate Immunity
Physical and Chemical Barriers
1. Skin
o Prevents invasion by microbes
o Protective protein Keratin
o Slightly acidic ~pH 5
o High [NaCl] with periodic drying
§ Fluctuation due to sweating in constantly changing environments
§ Acidic environment is a defence and can be inhibitory to Neutrophiles whose pH
range is between 5.5 - 8.5
o Mucous Membranes
§ Mucous traps microbes
§ Contains antimicrobial secretions
§ Ex. Lysozyme (page 16)
• Specifically cleaves b-1,4 glyosidic bonds in peptidoglycan
§ Ex. Defensins
• Antimicrobial peptides that poke holes in bacterial cell membranes
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2. Respiratory tract
o Mucociliary escalator
§ Ciliated cells line the mucous membranes of the airways
§ Sweeping action moves mucous and microbes away from the lungs
3. Gastrointestinal tract
o Stomach
§ Strong acidity (~pH 2)
§ Proteolytic enzymes
§ Destroys most microbes
o Small Intestine
§ Rapid change in pH (acidic to
basic)
§ Pancreatic enzymes
§ Bile
§ Destroy microbes
o Large Intestine
§ Like one big chemostat where
microbial growth rate is very
large
§ The normal microbiota
§ Microbes that already reside
in and on the human body
§ Take up attachment sites
§ Limited available nutrients
§ Make antimicrobial
compounds
4. Genitourinary tract
o Urine is metabolic waste product that
is toxic to many microbes
o Flushing action is the mechanical
removal of microbes
o Normal microbiota
§ Ex. Vaginal epithelial cells produce glycogen (food of microbiota)
§ Lactobacillus acidophilus ferments the glucose to lactic acid
• ~pH of 3-5
• Causes urine to be bacteriostatic and unfavourable for bacteria
• Without the formation of lactic acid, pH would increase, and yeasts can
start to grow in the urinary tract causing an infection
Cells and Organs of the Immune System
- The Lymphatic System
o A collection of tissues that bring specialized cells (lymphocytes) into contact with foreign
material (antigens)
o Made up of
§ Lymph vessels that carry fluid (lymph)
• Similar to blood, but contains white blood cells (leukocytes) instead of
red blood cells
§ Lymphoid Organs
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Lymphoid Organs
- Primary lymphoid organs
o Bone marrow and thymus
§ Leukocytes are produced and mature
- Secondary lymphoid organs
o Lymph nodes, spleen, MALT
o Contains leukocytes arranged to filter out microbes
and antigens
- Mucosa associated lymphoid tissue (MALT)
o Leukocytes constantly sample their surroundings by
phagocytosis looking for foreign material (early
warning system)
Leukocytes (WBC)
- Cells that circulate in the blood and lymph and reside in the lymphoid organs
- Involved in both branches of the immune response (innate and adaptive)
1. Granulocytes
o Cytoplasm contains granules filled with reactive chemicals
§ Can kill microbes
§ Signal other components of immunity
o 3 types of granulocytes
i. Basophils and mast cells
§ Granules stain with basic dyes
§ Non-phagocytic
§ Circulate in blood (basophils) or reside in mucosal tissue (mast cells)
§ Can be triggered to degranulate
§ Release vasoactive mediators
• Supposed to react to stimulus and trigger inflammation
• Some symptoms are for no reasons such as our allergies
Ø Result from too many basophils/mast cells
• Ex. Histamine
Ø Involved in the allergic response
ii. Eosinophils
§ Granules stain with acidic dyes
§ Non-phagocytic
§ Can leave the blood and enter tissues in areas of inflammation
§ Attack large parasites
• Protozoa and parasitic worms
§ Release reactive oxygen intermediates
• O2-, H2O2, OH∙
• Destroy parasite from the outside since it’s too big for phagocytosis
§ Pretty much circulates in the blood until they find site of inflammation and go
into tissues attacking large parasites through chemical interactions
iii. Neutrophils
§ Granules are filled with digestive enzymes
• Lysozyme
• Defensins
Document Summary
Immune system can be divided into two major branches. Innate (non-specific) immune response: exists at birth and always present, defends against all invaders equally, does not have memory. Responds against each invader the same way, every time it is encountered. Includes physical and chemical barriers, special immune system cells, physiological processes and molecular defenses: adaptive (acquired, specific) immune response, acts against a specific intruder, acquired when a pathogen is encountered for the first time, has memory. Responds more vigorously the second time a particular pathogen is encountered. Symptoms are barely felt: divided into two branches. Physical and chemical barriers: skin, prevents invasion by microbes, protective protein keratin, slightly acidic ~ph 5, high [nacl] with periodic drying. Fluctuation due to sweating in constantly changing environments. Acidic environment is a defence and can be inhibitory to neutrophiles whose ph range is between 5. 5 - 8. 5: mucous membranes. Lysozyme (page 16: specifically cleaves b-1,4 glyosidic bonds in peptidoglycan.
