microbio exam 4

Nonspecific chemical defenses

Sebaceous secretions, Lysozyme, High lactic acid and electrolyte concentration in sweat

innate defenses

Skin's acidic pH, HCl in stomach, antimicrobial chemical in semen

major histocompatibility complex

The MHC is a set of genes on chromosome 6 essential for acquired immune system to recognize foreign cells. They code for MHC glycoproteins. They distinguish self vs non self.

first line of defense

surface protection: intact skin, mucous membranes and their secretions, normal microbiota, lyzosyme

plasma cells

produce and secrete antibodies

helper t cells

Activate macrophages, B cells and T cells.

clonal deletion

The process of destroying B and T cells that react to self antigens (self specificity)

antigen presenting cells

dendritic cells, macrophages, B cells

Lyzozyme

An enzyme that breaks down pathogens on the skin's surface

Neutralization

antibodies covering surface receptors on a virus or toxin molecule, thereby disrupting their activity

MHC molecules are expressed on

all nucleated cells

Basophil

The rarest leukocyte that has histamine in the granules

keratin defense

creates a physical barrier against pathogens.

Eosinophil

white blood cell containing granules that stain red; associated with parasites

antigen

a foreign molecule that causes a specific immune response

Fc region

AKA the cystallizable fragment, stem of antibody that contains an effector molecule that can fix complements and bind to macrophages and mast cells

sterilization

The process that completely destroys all microbial life, including spores.

disinfection

A process that eliminates many or all microorganisms, with the exception of bacteria spores, from inanimate objects

most resistant microbes

prions and endospores

least resistant microbes

Viruses (enveloped and non enveloped) and gram-positive bacteria

factors that effect cell death rate

number of microorganisms, type of microorganism, temperature, ph, concentration

Cellular targets of physical and chemical agents

cell wall, cell membrane (DNA, RNA), proteins

Bacteriostatic

inhibits bacterial growth

Moist heat

lower temperatures and shorter exposure time; coagulation and denaturation of proteins

Dry heat

moderate to high temperatures; dehydration, alters protein structure; incineration and oxidation

normal microbiota is found in the

skin, upper respiratory system, GI tract, external genitalia, vagina

pathogenicity

ability to cause disease

Virulence

degree of pathogenicity

steps of a microbe causing disease

finding a portal of entry, attaching and negotiating the microbiome, surviving host defenses, causing damage, exiting

Viral adhesion mechanisms

fimbriae, capsules, spikes

endotoxin

A toxic component of the outer membrane of certain gram-negative bacteria that is released only when the bacteria die.

exotoxin

a toxin released by a living bacterial cell into its surroundings.

hemolysins

Toxins that lyse red blood cells.

course of infection

incubation period, prodromal stage, acute phase (height of infection) , convalescence (recovery)

horizontal transmission

disease is spread through a population from one infected individual to another

second line of defense

a cellular and chemical system that comes immediately into play if infectious agents make it past the surface defenses. ex: phagocytosis, inflammation

third line of defense

adaptive immunity, B cells and T cells

markers

Molecules on the surfaces of cells

composed of proteins and/or sugars

Evaluated by cells of the immune system

4 systems involved with first line of defense

skin, mucous membranes, respiratory, genitourinary

Phagocytosis steps

chemotaxis, ingestion, phagolysome formation, destruction, excremtion

Inflammation steps

1. injury: vasoconstriction and mast cell activation 2. vasodilation, clot begins to form 3. neutrophils come and edema occurs 4. scar formation, macrophages and lymphocytes

benefits of fever

Inhibits multiplication of temperature-sensitive microorganisms, impedes nutrition of bacteria by reducing the available iron, increases metabolism and stimulates immune reactions

interferon

Protein that induces the production of proteins that eliminate viral genes and block viral replication

4 antimicrobial products

interferons, complements, antimicrobial peptides, restriction factors

restriction factors

inhibit the multiplication of viruses in host cells

antimicrobial peptides

short peptides (between 12-15 aminos) capable of inserting themselves into bacterial membranes

class I MHC

found on all nucleated cells

class II MHC

found on antigen presenting cells (macrophages, dendritic cells, B cells)

clonal selection

antigens bind to specific receptors, causing a fraction of lymphocytes to clone themselves

immunoglobulins

b cell surface receptor

t cells

mature in the thymus, high concentration in the blood

b cells

mature in the bone marrow, low concentration in the blood, make antibodies

humoral immunity

specific immunity produced by B cells that produce antibodies that circulate in body fluids

cell-mediated immunity

type of immunity produced by T cells that attack infected or abnormal body cells

superantigens

potent T cell stimulators; can provoke a cytokine storm

helper t cells

CD4 only interact with class ii (antigen presenting) mhc cells

cytotoxic t cells

CD8 only interact with class i

epitope

Small, accessible portion of an antigen that can be recognized.

events in b cell activation

1. The B cell engulfs and processes a specific antigen.

2. The B cell uses an MHC class II molecule to present the antigen to the helper T cell.

3. The T cell binds to the MHC class II/antigen complex.

4. The B cell divides and the daughter B cells divide, resulting in plasma cells that produce antibodies.

events in t cell activation

A phagocytic cell processes an antigen and displays an antigen complex on its surface. The cell presents the antigen complex to CD8 cytotoxic T-cells.

active immunity

A form of acquired immunity in which the body produces its own antibodies against disease-causing antigens.

passive immunity

the short-term immunity that results from the introduction of antibodies from another person or animal

natural immunity

acquired as part of normal life experiences

artificial immunity

from medical procedures

Type I Hypersensitivity (immediate)

Immediate allergic reaction mediated by IgE (mast cells, basophils, etc)

Type II Hypersensitivity (antibody mediated)

labeled cytotoxic/ cytolytic & involve IgM or IgG interacting with foreign cells to cause their destruction (cell lysis) ex: incompatible blood groups

Type III Hypersensitivity (Immune Complex)

Type III hypersensitivity occurs when immune complexes, made of antigens and antibodies, build up in tissues. These complexes trigger inflammation and tissue damage. involves IgG

Type IV Hypersensitivity (Delayed)

Tissue damage caused by a delayed hypersensitivity response of T-lymphocytes to antigens. Symptoms arrive one to several days post exposure ex: contact dermatitis

oral inflammatory drugs

block production of IgE and inhibit lymphocyte activity.

atopy

chronic local allergy such as hay fever or asthma

lyse

Cell bursting.

six methods of physical control of microorganisms

heat, cold, desiccation, radiation, filtration, osmotic pressure

TDT (thermal death time)

Time required to kill a specific bacteria at a specific temperature

Thermal death point (TDP)

the lowest temperature required to kill all microbes in a sample in 10 minutes

Boiling water

Disinfection by boiling at 100°C for 30 minutes to destroy non-spore-forming pathogens items can easily be recontaminated

Pasteurization

treating a substance with heat to kill or slow the growth of pathogens, flash method is preferred because it doesn't change flavor and nutrients

Steam sterilization (autoclave)

utilizes moist heat in the form of saturated steam under pressure within an enclosed environment; the most dependable method of sterilization in which all microbes including spores are destroyed

Cold treatment

merely retards the activities of most microbes

lypophilization

method for preserving materials by freezing and then drying them directly from the frozen state

Ionizing radiation (X rays and gamma rays)

destroys DNA through mutations and damages proteins

nonionizing radiation

Atomic excitation leads to the formation of abnormal bonds

pyrimidine dimers

DNA mutations that result from UV exposure, damage to thymine and cytosine

Surfactants

A contraction of surface active agents; substances that allow oil and water to mix, or emulsify.

Degermation

reduces the number of microbes through mechanical means

Sanitization

remove vegetative life forms and debris to reduce contamination to safe levels

examples of surfactants

soaps, detergents, quats

Ethylene oxide

Sporicidal gas used to sterilize surgical instruments and other supplies but is toxic to humans

Halogens

Chlorine, iodine, fluorine, and bromine

Chlorine

Can kill endospores and sterilize, denatures proteind

Iodine

Interfere with metabolic functions and boding . Can be irritating to the skin.

Iodophors

Complex of iodine and alcohol

Have replaced free iodine solutions in medical antisepsis

hydrogen peroxide

Chemical compound of hydrogen and oxygen produces highly reactive free radicals and decomposes to oxygen

The granules of neutrophils contain

digestive enzymes

Pulse Field Gel Electrophoresis

• separation of DNA molecules in several directions