Microbiology Exam 4

What ways can a pathogen undermine the host immune response?

Suppress immune function (break down antibodies, infect cells, block signals, inhibit immune production) & Avoid phagocytosis (Capsule, block phagosome, neutralize hydrolytic enzymes, damage phagocytic cells)

What is the 5th step of infection?

A pathogen transmits to a new host to repeat the cycle

What role do symptoms play in the 5th step of infection?

Symptoms can facilitate transmission to others (sneezing/coughing, etc.)

What role do reservoirs play in the 5th step of infection?

Reservoirs allow the pathogen to live/thrive

What are the biosafety levels?

BSL1, BSL2, BSL2 plus, BSL3, BSL4

What are BSL1 agents?

Well characterized

Rarely cause disease

Not a high level threat

What are BSL2 agents?

Infectious agents

Not airborne

Most cause diseases that are preventable by vaccination or treatable by medication

What are BSL2 plus agents?

Level 2 agents

More dangerous

Not airborne

Not vaccine preventable

Ex: HIV virus

What are BSL3 agents?

Serious or lethal human diseases

Many of them are airborne

Some are treatable

Very severe

Only about 2000 facilities across the US

Ex: m. tuberculosis

What are BSL4 agents?

Dangerous and “exotic” pathogens

15 facilities across the US

Ex: Ebola

What are the classes of infection control?

Standard (universal) precautions & transmission precautions

When are standard infection control precautions used?

Used regardless of infection status

What precautions are used in STANDARD precautions?

Hand hygiene

PPE

Regular cleaning of surfaces

Proper clothing

Aseptic techniques

What precautions are used in TRANSMISSION precautions?

Isolation

Droplet precautions

When are transmission infection control precautions used?

When a patient is highly infectious

Immune

Has memory and takes time to build

Susceptible

Likelihood to be infected by a pathogen because we a) haven’t been exposed to the pathogen before and have no immune defenses or b) the pathogen has changed in such a way that our immune system does not recognize the pathogen

How are the adaptive and innate branches of the immune system different?

Innate immune system responds immediately with a general response. Adaptive immune system responds within 4-7 days with a specified response to the specific pathogen

How are the adaptive and innate immune systems alike?

Innate immune system and adaptive immune system work together to eliminate a pathogen

What role do our normal microbiota play in shaping the immune system?

Inducing, training, and calibrating immune responses

What are the first lines of innate immune defense?

Mechanical, Chemical, Physical

What is the role of the mechanical innate immune defense?

Flushing, rinsing, and trapping actions

What mechanical barriers are used in the innate immune defense?

Tears

Urine

Saliva

Mucous membranes

What is the role of the chemical innate immune defense?

Molecules directly attack microbes or generate an environment that limits their survival

What chemical barriers are used in the innate immune defense?

Lysozymes (found in tears, breast milk) & antimicrobial peptides (AMPs) (found in which blood cells, skin, mucous membranes)

What is the role of the physical innate immune defense?

Structurally blockade pathogen entry

What physical barriers are used in the innate immune defense?

Skin

What is the role of the lymphatic system in the innate immune response?

Collect, circulate, and filter fluid/lymph throughout the body tissues that screen for invaders

What are the primary lymphoid tissues?

Thymus and Bone Marrow

What is the role of primary lymphoid tissues?

Thymus: producing white blood cells

Bone Marrow: producing red & white blood cells

What are the secondary lymphoid tissues?

Adenoids, tonsils, lymph nodes, spleen, peyer’s patches, appendix

What is the role of secondary lymphoid tissues?

Screen for lymph invaders, lymph nodes swell if invader detected

Neutrophils

Exist in the largest numbers in relation to any of our white blood cells

First recruits

Release AMPs that destroy microbes and stimulate inflammation

Eosinophils

<5% of the total WBC population

Multi-nucleated

Basophils

<1% of the WBC population

Contain cytoplasmic granules (Histamines: stimulate inflammation)

Combat parasitic infections

Allergic responses occur within our body

Mast Cells

Reside in tissues

Release histamine

Conduct phagocytosis

Common in tissues near body openings

Promote earliest stages of inflammation

What do elevated neutrophils mean?

Bacterial infection

What do elevated eosinophils (Eosinophilia) mean?

Parasitic infection, asthma, or seasonal allergies

When do we see elevated basophils?

In certain types of blood cancer

What are the types of cytokines?

Chemokines, Interleukins, Interferons, Tumor necrosis factors

What role do chemokines play in immune response?

wound healing

formation of blood vessels

repair of blood vessels

developing lymphoid tissues

activate innate and adaptive immune systems

What role do interleukins (ILs) play in immune response?

Activate adaptive and innate immune responses

Stimulate hematopoiesis (process of creating new blood cells and platelets)

What does the IL-1 family do?

Involved in inflammation

help stimulate adaptive and innate immune response

Stimulation fever

What does the IL-2 family do?

Responsible for the development of T cells

Responsible for self tolerance

Trigger apoptosis

What role do interferons (IFs) play in immune response?

Send out signals when they detect a pathogen or tumor cell

Interfere with viral replication

Fight off bacteria, parasites, etc.

Trigger apoptosis of any neighboring cells that are already infected

Activate white blood cells

What role do Tumor necrosis factors (TNFs) play in immune response?

Stimulate inflammation In parts of the body where they detect damage

Kill tumor cells

Stimulate fever

What is the role of iron binding factors?

Provides vital nutrients to cells

What are the 3 outcomes of the complement cascade?

Opsonization, Cytolysis, Inflammation

What is the role of inflammation in healing?

Recruits immune defenses to the area

Limit the spread of infectious agents

Deliver oxygen, nutrients, and chemicals that help our tissues recover

What are the signs of inflammation?

Redness, pain, localized heat (not fever), swelling, loss of function

Why is chronic inflammation negative?

Not useful or protective

Exacerbates tissue’s injury and causes further damage to tissues

Promotes atherosclerosis, certain cancers, and progressive neurodegenerative disorders

What is the role of fever in the innate immune response?

Increases antiviral effects, increases efficiency of clearing invaders, enhances production of white blood cells, limits growth of pathogens, promotes tissue repair

Humoral Branch of adaptive immunity

Produces antibodies made by activated B cells

Cellular branch of adaptive immunity

Uses T cells

Steps of the adaptive immune response

1. Antigen presentation

2. Lymphocyte activation

3. Lymphocyte proliferation and differentiation

4. Antigen elimination and memory

What happens during step 1 of the adaptive immune response, antigen presentation?

Antigen presenting cells will take an antigen from a pathogen and present it to the T and B cells, who will recognize the particular antigen

Role of T cells in the adaptive immune response

Mobilize against diverse antigens

Role of B cells in the adaptive immune response

Produce antibodies

Hapten

Incomplete antigens

Epitope

Parts of the antigen that are recognized by our B and T cells

How do B cells recognize diverse epitopes?

B cell receptors bind directly to the epitope of the antigen

How do T cells recognize diverse epitopes?

Antigen presenting cells present the epitope to the T cell receptors

Cytotoxic T cell

Directly destroy infected cells, cancer cells, and transplanted tissues

Helper T cell

Release cytokines that can stimulate or suppress other white blood cells. Don’t directly go after the invader, activate t cytotoxic cells and B cells

Role of MHC I

Present intracellular antigens to T Cytotoxic cells

Role of MHC II

Presenting extracellular antigens to T helper cells

Why do we have two different types of MHC?

Antigens can exist in two locations (intracellular - MHC I, extracellular - MHC II)

T-independent activation path for B cells

B cell will bind to different epitopes of antigens on multiple different B cell receptors

T-dependent activation path for B cells

1. Antigen binds directly to the b cell

2. Antigen interacts with MHCII

3. T helper cell binds to the antigen and releases cytokines which secondarily activate B cells

Plasma cells

B effector cells that make antibodies

Role of plasma cells in the adaptive immune system

neutralize antigens, activate complement, increase phagocytosis

How do antibodies eliminate pathogens?

Neutralize toxins/antigens by binding to them, complement cascades (lead to cytolysis, opsonization, or increase phagocytosis)

Structure of antibodies

“Y”-shaped molecule. Stem portion that has antigen binding sites

Isotope switching

Altering which class of antibody we are making based on constant region

IgG

Found in blood, all bodily fluids

If detected in a patient to a particular antigen of interest, at some point that patient has been exposed to that particular antigen (whether they know it or not)

IgA

Second most abundant

Found in mucus, mucous membranes, all bodily secretions (tears, saliva, sweat, etc.)

IgM

Found mostly in blood

Antibody that is made early in an infection during a primary antigen exposure

IgE

Found in really low concentration

Found in lungs, skin, mucous membranes

Plays a role in allergies (causes some of the cells of our innate immune system to release molecules in response to allergy)

IgD

Very sparsely represented

Found on the surface of b cells

Not well understood

What happens with immunoglobins on a primary antigen exposure?

IgM is present after about 4 days, IgG is present after about 7

What happens with immunoglobins on a secondary antigen exposure?

Both IgG and IgM are present immediately after exposure, but IgG levels are much higher and long-lived than IgM and IgG during primary exposure

Naturally acquired active immunity

Immunity from a previous infection

Naturally acquired passive immunity

Antibodies passed across the placenta

Artificially acquired active immunity

Vaccination triggers immune response

Artificially acquired passive immunity

Antivenom neutralized toxins