The Immune System - Body Defenses Lecture 3 PDF

THE IMMUNE SYSTEM - BODY DEFENSES LECTURE 3 Wednesday, October 4, 2023 10:55 PM INTRODUCTION → Most immune cells don't circulate in the blood → Immunity: is the body's ability to protect itself by resisting or eliminating potentially harmful foreign invaders (e.g. bacteria and viruses...

THE IMMUNE SYSTEM - BODY DEFENSES LECTURE 3 Wednesday, October 4, 2023 10:55 PM INTRODUCTION → Most immune cells don't circulate in the blood → Immunity: is the body's ability to protect itself by resisting or eliminating potentially harmful foreign invaders (e.g. bacteria and viruses) or abnormal cells (e.g. cancer cells) i.e. foreign to the "normal self" - your normal cells → Immune system activities: ○ The reason we're alive ○ Defends against invading pathogens ○ Removes "worn-out" cells and tissue damaged by trauma ○ Identifies and destroys abnormal or mutant cells that have originated in the body called immune surveillance (bad actors) ○ Mounts inappropriate immune responses that lead either to allergies or to autoimmune diseases § Bee stings, allergic reactions are sometimes due to the body overreacting or being misdirected § Immune cells are attacking your own healthy cells IMMUNITY: PATHOGENIC MICROBES → Bacteria: ○ Non-nucleated, single celled microorganisms ○ Primarily cause tissue damage and cause disease by releasing enzymes or toxins (reason for vaccines) § Don't damage bc they want to but bc they divide constantly § Ex: chlamydia, Streptococcus, E.coli, Salmonella → Viruses ○ Consists of either DNA or RNA, (not both) enclosed by a protein coat ○ Cannot carry out metabolism or reproduce without invading a host cell (non-self sustaining entities) ○ Ex: SARS-CoV-2, HIVV, HCV, Influenza, Ebola, Polio (causes paralysis) ○ Most common is respiratory viruses → Fungi, ex: aspergillus, Candida → Parasites ○ Protozoan parasites ex: plasmodium malaria ○ Helminth parasites (worms) → Notion of virulence: the inherent ability of a pathogen to cause disease ○ Not all pathogens have the same capacity ○ Can be strong or weak IMMUNITY: EXTERNAL DEFENSES → Mechanical ○ Major role in preventing pathogens from entering ○ Air / food / water / through genitals are the most common way for pathogens to enter ○ Nasal cilia can trap bacteria ○ In burn victims they go to hospitals not to treat the pain but to stop infection → Chemical ○ We make antimicrobial peptides § Made by epithelial cells § They're always there § Act as protectors → Microbiological ○ Microbiota (bacteria) is found in the gut or skin ○ Compete for same resources - space and food ○ Can make substances that prevent pathogens from multiplying ○ Best kinds are found on FIBER IMMUNITY: INTERNAL DEFENSES → Plan B: position strategically, special delivery system that allow immune cells to move → Lymphoid Tissue: tissues that produce, store, or process lymphocytes, including: ○ Bone marrow - where immune cells are made and divide - Once immune cells are developed they leave and circulate in the blood or lymphatic vessels ○ Thymus - where T cells divide and mature and are made → Lymph nodes - checkpoints, drain the lymph and the cells in it to check for foreign antigens ○ B / T cells check these nodes and circulate with the blood to check for pathogens → Spleen - has patches, white pulp with immune cells → Tonsils - smaller nodes and have higher chance of entry in mouth → Adenoids - in the pharynx → Appendix - has immune function → Peyer's patches or GALT ) gut-associated lymphoid tissue - found in gut and lungs due to higher pathogen exposure → Strategically located to intercept invading microorganisms before they have a chance to spread very far IMUNITY: FUNCTIONS OF LYMPHOID TISSUES IMMUNITY: IMMUNE RESPONSES → Two immune responses: innate and adaptive ○ Innate responses that nonselective (don't care, not specific ) defend against foreign material § First line of defense, "non-specific", rapid but limited response § Defense include the following: □ Inflammation □ Interferons (anti-viral) -> best defense against viruses ( innately ) □ Natural killers cells (NK) □ Complement system - Liver makes compliment protein □ Dendritic cells ® Important ® Don't circulate ® Resident ® Sit in tissue (lungs, liver, skin, spleen) ® Drink large amounts of fluid ® If they drink a pathogen: they get activated the leave go to lymph nodes and activate the T cells ® Non-selective ○ Adaptive responses that selectively target particular invaders § Antibody-mediated immunity (humoral) □ Involves production of antibodies by plasma cells (B-lymphocyte derivatives) □ Mediated by B-cells § Cell-mediated immunity □ Involves production of activated T lymphocytes □ Directly attack unwanted cells □ Mediated by T cells □ Cell to cell action → Pathogen will grow to fast to be attacked, no control → Pathogen can be initially controlled, but you can lose control b/c you can't really clear it → Normal, immune system kicks in and pathogen will cease to exist → Innate: rapid, non-specific, occurs early → Adaptive response: is developed after encountered with pathogen, specific → Remember that some innate immune cells are required to activate the adaptive system