A&P lecture microbiology and immunology/defense

prokaryotic cell vs eukaryotic cell

prokaryotic has no nucleus or organelles making it smaller, eukaryotic cells have a nucleus and organelles making them much larger and complex.

different types of bacteria

• obligate aerobes

• obligate anaerobes

• facultative anaerobes (can live in anaerobic and aerobic)

• live in extreme conditions

• may form endospores (can survive anything)

bacteria morphology

unicellular but often live in “groups”

good vs bad bacteria

small fraction cause infection or illness, most are harmless. Some are opportunistic pathogens (normally not but can become pathogenic).

normal flora

the bacteria, fungi, and viruses that live in/on our bodies all the time

bacterial cells of normal flora

body contains same amount of human cells as it does bacterial cells but are not found in urine, blood, lymph, or CSF.

locations of bacteria in our body

skin, digestive tract, and respiratory tract act as mini ecosystems to bacteria, providing us with specific benefits.

controlling bacterial infections

• antiseptics and disinfectant can kill bacteria or inhibit their growth.

• Antibiotics and antimicrobial drugs prevent growth but are not toxic to host with minimal side effects (can lead to antibiotic resistance)

antibiotic resistance

one “generation” for bacteria is a short period of time, many generations = more opportunities for random mutations that could make the bacteria resistant to the antibiotics.

viruses structure

• acellular (no cell membrane)

• cant reproduce on their own

• cant make/use their own energy (invades host cells cellular machinery to copy genetic info and make more particles)

• genetic info contained in a “protein coat”

lytic cycle

virus invades host cell, makes new copies of the virus, then causes lysis of the host cell to release the virus.

lysogenic cycle

virus invades host cell, viral DNA gets incorporated into host genome and stays there until a condition changes (can be long time). Can later re-enter the lytic cycle.

control of viral infection

• hand washing

• avoiding germs

• masks

• vaccination

• antiviral medications disrupt but can be harmful to host

fungi structure

• eukaryotic cells but have unique cell wall

• not always microscopic (mushrooms vs yeast)

• part of our normal flora but can be opportunistic pathogens

• common ones: thrush, athletes foot, ring worm

control of fungal infections

• anti fungal medication (sometimes toxic to human cells)

• fungal pathogens develop resistance

protozoa structure

• eukaryotic

• unicellular

• most aren’t pathogenic but some are important pathogens with serious effects on human health

• complex lifestyles involving more than one host

• associated with contaminated drinking water

• typically have locomotion

control of protozoan infection

• avoid contact

• ensure access to clean drinking water

• vaccines

metazoan parasites structure

• eukaryotic

• multicellular (bigger, complex)

• adult form can be large and visible but are often identified by eggs or larval from (microscopic)

• can include pinworm, tapeworm, filariasis

control of metazoan infections

• avoid contact (uncooked meat, skin, fecal-oral route)

• some medications are available

• antibiotics to kill bacteria in the gut of the parasite

ways microorganisms can cause disease

• consuming nutrients/resources in your body

• triggering vomiting/diarrhea

• causing structural damage

• provoking an immune response

• disrupting your normal flora

nosocomial infections

acquired in a clinical setting due to poor hand hygiene, antibiotic resistant strains of bacteria, resistant endospores, patients are more susceptible.

barrier defences

skin forms a tight barrier, mucous traps pathogens, clotting response prevents pathogens from entering.

adaptive responses

lymphocytes are capable of response and cells of the immune system use secreted signals and cell-to-cell interactions to communicate

cells associated with innate defenses

phagocytic cells destroy/engulf pathogens, granular cells harm/kill pathogens, cells of immune system communicate via cytokines

innate immunity (non-specific)

• born with it

• defense against anything foreign/abnormal

• first line of defense

• includes physical barriers, NK cells, inflammation, etc.

adaptive immunity (specific)

• develops after birth, after exposure to antigen

• 4 properties (specificity, versatility, memory, tolerance)

• includes actions of cytotoxic T cells and B cells.

specificity

ability to target specific cells

versatility

ability to respond/build defences against things we don’t know exist and adapt to environment

memory

ready to act quick if exposed again because our body remembers

tolerance

need to destroy other cells but not our normal ones

communication across cell membranes

• antigens are “specific chemical targets” that stimulate immune response and be displayed on surface of cells (MHC)

• body can detect “self” from “non-self” antigens

antigen presenting cells

• pick up and display antigens on their surface without being infected themselves

• have class II MHC proteins on their membranes

• activate helper T cells

• includes dendritic cells, macrophages, microglia.

NK cells

• non-specific

• recognize foreign antigens/abnormal antigens on cells

• release perforins to create holes in target cells and destroy

• destroy body cells infected by viruses (including cancer cells)

T cells/lymphocytes

• cell-mediated immunity (attack by phagocytosis)

• formed in bone marrow but developed in thymus

• T cell receptors and CD markers on membranes

• includes helper T cells, cytotoxic T cells, memory T cells, regulatory T cells

B cells/lymphocytes

• antibody-mediated immunity

• formed in bone marrow

• B cell receptors and class II MHC proteins on membrane

• includes inactive B cells, sensitized B cells, plasma cells, memory B cells

what happens if there is a “breach” in immune response?

innate defenses keep thing under control until specific defenses are ready where they will destroy the specific antigen.

class I MHC

• on all nucleated cells

• communicates with CD8 T cells (cytotoxic T cells)

• results in destruction of infected cell

class II MHC

• on specialized cells (APCs, B cells)

• communicates with CD4 T cells (helper T cells)

• results in stimulation of immune response

IgG antibodies

largest, account for 80% of antibodies, responsible for resistance against viruses, bacteria, and bacterial toxins.

IgE antibodies

attaches as an individual molecule to the exposed surfaces of basophils and mast cells. Causes stimulation of a cell to release histamine.

IgD antibodies

is an individual molecule on the surfaces of B cells where it binds antigens in the extracellular fluid.

IgM antibodies

first class of antibody secreted after an antigen is encountered, circulates as a five-antibody starburst.

IgA antibodies

found in glandular secretions such as mucous, tears, saliva, and semen. Attack pathogens. before they gain access to internal tissues.

primary response

first exposure to specific antigen, takes time to develop; some IgM first then IgG

secondary response

second exposure to same antigen, much more rapid as you are now “immune” to the pathogen. Some IgM but much more IgG

artificially acquired active immunity (vaccines)

antigen is administered triggering immune response, individual will produce antibodies against the antigen so youre ready if ever exposed to the “real” antigen

inflammation

• non-specific defense

• innate

• a response to invasion/infection, tissue damage, or both

• symptoms include redness, heat, swelling, and pain

purpose of inflammation

deliver leukocytes and plasma proteins to site of injury to destroy any invaders, clean up the mess, and facilitate healing/repair

how do cells get to inflammation sites?

mast cells release histamine triggering vasodilation and increased capillary permeability. Neutrophils and monocytes also undergo margination and diapedesis.

immunological surveillance and cancer

any cell may undergo a mutation that affects its cell division, becoming cancerous. cancer cells are “self” but are abnormal so can be recognized by your body defenses.

balance between immunity and autoimmunity

immune response is essential to preventing infection but an overactive immune response could lead to autoimmunity.