BIO CHP 28

Any foreign substance that elicts an immune system response

• Generally proteins or carbs from an invading organism
• "antibody generator"

• EXAMPLES:
• pollen and other allergens,
• bacteria
• viruses
• poison ivy (oil)
• etc.

All different varieties of white blood cells

• Proteins can:
• -Destroy antigens
• Mark antigens for destruction
• OR
• -communication molecules

• The immune system has two primary defensive strategies:
• --Nonspecific defenses: do not discriminate between one invader or the next
• --Specific defenses: provide protection against particular invaders

• Set of barriers
• -like skin cells
• and secretions produced by the barriers

• EXAMPLE:
• antimicrobial properties of skin, acid secretions in stomach, sweat, oils, tears, saliva, cilia on lungs

• mount a coordinate action:
• the inflammatory response

• Invovles cells and proteins that kill invaders
• and substances that increase blood flow and blood vessel permeability near injury site (like histamine)

Immunity that results from coming into contact with an antigen

Passively acquired immunity: from transmission of disease-fighting antibodies produced by another individual

• Actively acquired immunity: develops from natural or deliberate exposure to an antigen
• --Can be from getting an immunization shot or by catching a disease (like chicken pox)

• Two Major Divisions:
• 1. Antibody-mediated: works by production of proteins called antibodies
• --Bind to a particular antigen and can be:
• *Receptors on the surfaces of B cells
• *Free-standing proteins: secreted by B cells

2. Cell-mediated immunity: cells destroy body's infected cells

• White blood cells
• ~b-lymphocyte cell (B cell): central to antibody-mediated immunity
• ~T-lymphocyte (T cell): central to cell-mediated immunity and helps initiate-mediated immunity
• so, critial in both forms

• B and T cells found throughout lymphatic system
• ~vessels captures fludis leaked from bloodstream
• ~subjects these fluids to scrutiny by immune system cells, then returns them to bloodstream

• Antibodies limit infectious attacks:
• -binding with antigens keeps antigen from binding with anything else
• -can bind to invaders in a way that macrophages can bind wiht the invaders and kill them

• Provides Protection when the body's own cells infected by an invader
• -viruses and some bacteria can infect the body's cells and remain inside them, so no antibodies can't access

• Central player: THE T CELL
• 3 varieties

• 3 varieties
• ~Helper T cells: reognizes viral structures displayed on body cell's surface
• ~Cytoxic (or killer) T Cell: kills body's own infected cells
• ~Regulatory T cells: protects body's own tissue from attack

• When white blood cells (many kinds) kill cell invaders...
• -they display protein fragments from them on their cell surfaces
• -fragments now serve as antigens
• -any cell that plays does this in an antigen-presenting cell (APC)

• The immune system can attack the body's own healthy tissues
• -Mistake body's tissues ("self") for foreign substances ("nonself")

• EXAMPLES:
• Rheumatoid arthritis: attack connective tissue
• multiple sclerosis: attack nerve tissue
• Type 1 Diabetes: attack insulin-producing pancreas cells

Immune system overreaction to a foreign substance (allergen)

Causes relase of infectioin-fighting compound histamine

• Inflammatory response ranges..
• -from small and harmless (sneezing and sniffling)
• -to large and life-threatinging (asthma or anaphylatic shock)

caused by HIV: Human Immunodeficieny Virus

• VIrus is devastating for several reasons:
• -Attacks the immune system itself
• -Invasion leads to a harmful infection rapidly
• -its genetic material mutates rapidly

the virus itself changes shape at a rapid rate and can invade the immune system undetected.

Once inside, virus inserts copy of its own genetic material into T cell's DNA

• can stay inactive for extended periods of time dieen from immune system.
• -genes are still replicating with T cell genome

• Also, can use infected cell's metabolic machinery to make its own proteins and genetic material
• -that is, make more viruses
• -which leave cell to go infect others
• -T cells eventually die

• T cells are central to immunity
• -under attack from HIV, many die
• -leaving body vulnerable to other invaders
• -AIDS diagnosed when lymphocyte count is below 200 per micro liter of blood
• -AIDS victims don't die of AIDS exactly but from a common infection (cold, flu, etc.)

• Very difficult to develop a vaccine to prevent AIDS
• -would have to prevent infection of all T cells
• -its constantly changing
• -perhaps an AIDS vaccine will only slow down replication of HIV

• Multiple Stages:
• Initial infection: rapid viral spread, antibody production, flu-liek symptoms
• asymptomic phase: # free virus decreases, last few months to several years
• disease progression: virus increases again, muatates
• -Eventually patient succumbs to opportunistic infection

• •High-risk category
• –Unprotected
• sex
• –Anything
• involving passage of blood, vaginal fluid, semen
• –Transmission
• from mother to child before birth

• •Intermediate-risk
• –Protected
• sex
• –Mother
• to child: through breast milk
• –Blood
• transfusions & organ transplants before 1987

• •Low-risk
• –Sharing
• razors/toothbrushes
• –Tatooed/Pierced by
• un-researched source

• •Very low/No-risk
• –Shaking
• hands, sharing a toilet, sneezed on, being in same room, mosquito transmission

• •Originated
• in Sub-Saharan Africa in late 19th/Early 20th
• Century

• –Lots
• of urbanization/colonization going on
• –Evolved
• from primate virus: Simian Immunodeficiency Virus (SIV)

• •Probably
• from blood exchange while hunting or butchering: “bushmeat”

• •But
• SIV does not appear fatal for primates

25+ million deaths between 1981-2005

• -most in Sub-Saharan African
• -Asia = 2nd

• Reasons:
• - First found in U.S. among intravenous drug uses and gay men who developed rare skin cancer.