MICRO 212: 32-34

Complete each sentence about the steps involved in the molecular events resulting in T-cell activation.

All naïve T cells, whether CD4+ or CD8+ cells, require two signals to be activated into effector cells. Signal 1 occurs when an antigen fragment, presented in an MHC molecule of an antigen presenting cell (APC), fills the appropriate T-cell receptor. In the case of T-helper (TH) cells, antigen is presented by class II MHCmolecules, which triggers CD41 coreceptors on the TH cell to interactwith the antigen-bound MHC molecule. For CD8+ cells to be activated, an endogenous antigen is presented in class I MHC molecules on the APC, and the CD8 coreceptor on the T cell interacts with the antigen-bound MHC molecule on the APC to induce CTL function. In addition to the first signal, both naïve CD4+ and CD8+ cells require a second, co-stimulatory signal to become activated. The most important second signal seems to be the B7 (CD80) protein on the surface of an APC, which binds to the CD28 receptor on the T cell.

How is an antiseptic different from a disinfectant?

An antiseptic is used to remove or kill microorganisms on tissue, whereas a disinfectant is used to remove or kill microorganisms on inanimate objects.

The activation of self-reactive T and B cells that, following stimulation by genetic or environmental triggers, results in actual tissue damage is known as _______ disease

Autoimmune

Which of the following statements is true about immune disorders?

Autoimmune disease results from the activation of self-reactive T and B cells that, following stimulation by genetic or environmental triggers, cause actual tissue damage

Place these types of bacteria in order of their susceptibility to chemical disinfection, from least susceptible to most susceptible

Bacterial endospores: 1 Gram-negative bacteria: 3 Gram-positive bacteria: 4 Acid-fast bacteria: 2

Which of the following represents a direct mechanism of microbiome-pathogen colonization resistance?

Bacteriocins released by Gram-positive bacteria target closely-related species

Which of the following statements is true about the susceptibility of antigens to antibody action?

Because antibodies have at least two antigen-binding sites and most antigens have at least two epitopes, cross-linking can occur, producing large aggregates termed immune complexes.

Choose the correct statement about T cells and their cluster of differentiation receptors.

CD3 is a heterodimeric receptor found on all T cells; it can be one of two possible TCR dimers, either alpha/beta or gamma/delta.

Cytokines are soluble substances that play important roles in communication in the host resistance systems. Match the specific cytokines with the role that they play

Colony-stimulating factors - growth and differentiation of leukocytes Tumor necrosis factors - increase coagulation response Interleukins - produced by one leukocyte to influence another Interferons - increase immunity to viral infection Chemokines - cell recruitment and direction of movement

The human host and its normal microflora produce many different chemicals that have antimicrobial action. Match the host mediator with a specific characteristic of that substance.

Defensin - can stimulate mast cell degranulation Bacteriocin - toxic proteins released by normal bacterial microbiota Cathelicidin - linear, alpha-helical peptides that lack cysteine amino acids Histatin - has antifungal activity

Which of the following statements is not true about the generation of diversity in antibodies?

During somatic mutation, repair of the base pair mismatch is error-free, allowing no further sequence diversity.

A product is defined as a probiotic if it is a compound that enhances the colonization and positive health benefits of the microbiome

False

Both neutrophils and macrophages are active phagocytic cells. When comparing tissue distribution for these two cell types, neutrophils predominantly take up residence in specific tissues once they mature, whereas macrophages remain in the blood until they are stimulated to migrate.

False

T-dependent antigen triggering of a B cell requires previous antigen presentation to the TH2 by a dendritic cell; this presentation must be in conjunction with a MHC class _____ molecule.

II

The immunoglobulin receptor molecules on the B-cell surface associate with other proteins known as the ________.

Ig-alpha/Ig-beta heterodimer proteins

Classify the statements that describe the effect of the gut microbiome on the CNS according to the mechanism they influence

Immune System - Dysbiosis causes LPS to leak across gut and triggers pro-inflammatory cytokines and disease Vagus Nerve - Gut bacteria stimulate enteric neurons providing a connection between the gut and the brain Blood-Brain Barrier - Small-chain fatty acids produced by the microbiota maintain tight junctions between cells

Please choose the method of antimicrobial susceptibility testing that involves measuring and evaluating zones of inhibition around antibiotic disks placed on a culture of bacteria prior to incubation.

Kirby-Bauer test

Many different components play a role in the mammalian host immune system. Match the components of an immune response with a description of the role that they play.

Lysozyme - an antimicrobial chemical Antigen - a foreign substance that provokes an immune response Leukocytes - function in both innate and adaptive immunity Antibody - glycoprotein that binds to a specific antigen

What is the primary role of the MALT?

MALT is in place to defend underlying tissue from potential pathogens in contact with the lumen.

When a host organism rejects transplanted tissue, the most important target is the _________ molecules (found on all nucleated cells) present on the transplanted tissue

MHC class I

Drag the labels to complete each of the sentences that discuss the interconnectedness of the innate and specific immune responses.

Macrophages and {dendritic} cells play a crucial role in bridging the innate immune responses with adaptive immunity. Both cell types have membrane-bound {pattern recognition molecules} (PRMs), which bind to the microbe-associated molecular patterns (MAMPs) of pathogen {macromolecules}. Once a pathogen is recognized by the phagocytic cell, the process of {phagocytosis} ends with the antigenic remains of the microbe being presented on the surface of the cell where it is carried to the {lymphoid} tissue. There, the antigens are presented to naïve {T lymphocytes}, which respond by stimulating additional lymphocytes to recognize that specific antigen and retain a {memory} of its antigenic signature.

Leukocytes, or white blood cells, are the cells responsible for the innate defenses. Match the different leukocytes with a key characteristic

Monocyte - mature into macrophages Neutrophil - principal phagocytic responder in blood Basophil - a granulocyte that contains histamine Macrophage - the largest phagocytic cell in the body Dendritic cell - present antigens to lymphocytes Mast cell - vasoactive mediators Eosinophil - important in defense against protozoan and helminth parasites

Which type of antibiotic is most likely to target the pathogen without causing a decrease in the normal microbiota?

Narrow spectrum

Recent reports confirm the impact of normal microbiota on human health and the presence of a relatively high number of gut firmicutes is strongly correlated with type 2 diabetes and _______.

Obesity

Which of the following statements is true about clonal selection of lymphocytes?

Once a lymphocyte has been released from its primary development site and is exposed to its specific antigen, it proliferates to form a clone (a population of identical cells derived from a single parent cell).

The process by which microorganisms or other foreign particles are coated with antibody or complement and thus prepared for "recognition" and ingestion by phagocytic cells is known as ________.

Opsonization

After a B cell is activated by its specific antigen, the first type of antibody secreted is the _________ form of IgM.

Pentameric

To distinguish between self and non-self, each cell must express _______ on its surface that mark it as a resident of that host; these are encoded by the major histocompatibility gene complex.

Proteins

Which of the following molecules can serve as antigens?

Proteins, nucleoproteins, polysaccharides, and glycolipids

Dendritic cells are found in these locations of the human host. (Check all that apply.)

Skin Mucous membranes of the intestines Brain

Which two types of bacteria listed below are moderately resistant to microbial control methods?

Staphylococcus aureus E. coli Pseudomonas aeruginosa Mycobacterium tuberculosis

Which of the following statements about activation of B cells is correct?

The T-independent antigens tend to be polymeric; that is, they are composed of repeating sugars or amino acids, and the resulting antibody generally has a relatively low affinity for antigen.

Which of the following statements is correct about the types of molecules that can serve as antigens?

The ability of a molecule to function as an antigen depends on its size, structural complexity, chemical nature, and degree of foreignness to the host.

Which of the following statements is correct about antigen presentation by class I and class II MHC molecules?

The class I MHC molecule is presented on the surface together with its endogenous antigen, enabling the host cell to present the antigen to a subset of T cells known as cytotoxic T lymphocytes.

How should the zone of inhibition be measured?

The diameter of the zone (in mm) is measured, from one edge of the zone, across the disk, to the other edge of the zone.

Select all statements that accurately describe results obtained through the human microbiome project and other human microbiome studies

The human microbiome varies significantly among individuals. Autoimmune disease is determined entirely by the genes one inherits Obesity is associated with limited microbial diversity in the gut. The gut microbiome is essential in stimulating immune system maturation.

Examine microbial communities comprising the normal flora of the human body to understand the causes and consequences of colonization by completing each sentence.

The many microorganisms that live in close association with humans are termed normal human microbiota or microflora. The skin harbors resident bacteria that normally grow on skin and transient bacteria that are only temporarily present. The skin surface is dry and salty, and glands release enzymes such as lysozyme as well as antimicrobial peptides called cathelicidins The most common skin bacteria include members of the Staphylococcus genus, namely S. aureus and S. epidermidis. Staphylococcus also are found in the nasopharynx, along with a group of nonpathogenic diphtheroids that resemble Corynebacterium. The lower respiratory tract is not sterile but has limited microbiota, since mucus, ciliated epithelial cells, and alveolar macrophages are all utilized for protection from microbial invasion. The genitourinary tract harbors some organisms with the major organism Lactobacillus of the vagina being important in lowering pH and preventing fungal growth.

Which of the statements is false concerning the role of the spleen in immune function?

The spleen is a primary lymphoid organ

Which of the following steps in a disk diffusion test for antimicrobial sensitivity is completed first?

The test microorganism is spread over the surface of an agar plate.

Complete each sentence about the localization of B and T cells during development

To begin, B- and T-cell {progenitor cells} (maybe) develop in the embryonic bone marrow and relocate to specialized tissue sites, called microenvironments, for maturation. The {B cells} relocate to microenvironments within the bone marrow, leaving to seed secondary tissue sites when they are fully mature. The T-cell progenitors initially leave the bone marrow and migrate to the {thymus}, where they develop into at least four subsets of T cells. They also populate secondary {lymphoid} (maybe) tissue sites once they mature. Mature B cells and T cells are induced to elicit an {effector} response when a foreign, nonself material is detected. A successful response either eliminates the {foreign} material or renders it harmless to the host.

Which of the following statements about cluster of differentiation (CDs) molecules is correct?

Unfortunately, the presence of various CDs on the cell's surface cannot be used to determine the cell's identity. or CDs have both biological and diagnostic significance. They can be measured in situ and from peripheral blood, biopsy samples, or other body fluids. (I think this one)

Erythroblastosis fetalis can occur when _________.

a Rh− mother is pregnant with a second Rh+ fetus and she has not had an injection of RhoGAM

The ability to recognize a specific antigen and remember it in the future is a characteristic of the ________.

adaptive immune response

A chemical compound, regardless of its source (either natural or synthetic), that is capable of killing or inhibiting microorganisms is referred to as

an antimicrobial.

The presence of a granuloma is an indication of ________.

chronic inflammation

Due to the acidic environment of the stomach, gastric juices ________.

contain a few viable bacteria per milliliter: maybe

Digestion of a pathogen within a phagolysosome involves all of the following EXCEPT _________.

high pH in the phagolysosome that denatures pathogen proteins: maybe

The importance of the human gut microbiota on metabolism is that ________.

human cells metabolize relatively few molecules into usable calories; most of our cellular energy is derived from microbial metabolism

A fundamental pathology of metabolic syndrome stems from __________.

insulin resistance

Bifidobacteria are an essential component of host defense against pathogens and are required for ________.

normal development of GALT

On the skin, Propionibacterium acnes converts lipids secreted by the oil glands to unsaturated fatty acids, such as ________ ________, that have strong antimicrobial activity against Gram-negative bacteria and some fungi.

oleic acid

Leukocytes detect the presence of pathogens by looking for ________.

pathogen-associated molecular patterns (PAMPs)

An example of a molecule that acts as a hapten is ________.

penicillin

The broad basis of the relationship between microbes and cancer in the human host is __________.

the ability of microbes to disrupt the normal cell cycle and to damage or mutate DNA

The _________ regions of antibodies have different amino acid sequences, and these regions fold together to form the antigen-binding sites.

variable

Humans are holobionts; they contain approximately three times as many microbial cells as human cells. Recent metagenomic investigations reveal that human microbial flora is extremely diverse and is best described as ________.

vital to our survival

The clear area devoid of bacterial growth around an antiseptic or disinfectant disk is referred to as the

zone of inhibition.