Immuno PPT Flashcards Unit 4
Conventional laboratory diagnosis of parasitic and fungal diseases is determined by observing what? / Morphological features of parasites and culture (in the case of fungi).The antigens for what organisms are often cruder than for viral and bacterial diagnosis and that`s why serological testing is limited? / parasites and fungi
Because the antigens for parasites and fungi are often cruder and serological testing is limited is result of what? / decreased specificity in many diagnostic procedures
Until the emergence of what infection, parasitic infections were uncommon in the United States? / HIV
With the spread of what disease toxoplasmosis, giardiasis, and cryptosporidiosis have become more important problems? / AIDS
With the spread of AIDS, what infections have become more important problems? / toxoplasmosis, giardiasis, and cryptosporidiosis
What parasitic diseases are the most harmful infective diseases afflicting humans worldwide? / malaria, schistosomiasis, and leishmaniosis
When a parasite enters a host no infection may result because of what? / the host’s innate immunity prevents the parasite from establishing an infection
When a parasite enters a host what one of possible result may occur? / Parasite may be killed and eliminated by host defense mechanisms
When a parasite enters a host what one of possible result may occur? / the parasite may overwhelm and kill the host
When a parasite enters a host what one of possible result is a long-lasting infection in which what occurs? / the host begins to eliminate the parasite but cannot remove it completely
When a parasite enters a host what one of possible result may occur? / the host mounts a response that attacks the parasite and host tissues
As a host defends itself, the parasite attempts to what? / evade hast’s defense mechanisms
Large organisms that are very antigenically complex and have complex life cycles are? / Parasites
In various body locations may be found: / Different stages of parasite
Situation in which the host may partially control the infection but not eliminate the parasite is leaded by? / Net result
The parasite is protected in host’s cell when: / parasite becomes sequestered
When the parasites leave these cells and move between other cells, they are: / vulnerable to the host’s defenses
Some parasites disguise themselves by what? / acquiring host antigens
The process of evasion some parasites employ is called: / antigenic variation
The host builds what antibody to reducing the infection? / IgM
How does the parasite respond to making the current antibody ineffective? / by changing its antigen
How long does the process of antigen switching continue for? / Long periods of time
What is another mechanism of escape for parasites? / Antigen shed
Why is the immune response unable to harm the offending organism of the parasite? / The antigen is not attached to the parasite
What may result from molecular mimicry? / Parasitic antigens that are similar to antigens normally found on host tissue
What may molecular mimicry lead to? / Autoimmune problems
Why is the host rarely able to totally eliminate the source of infection? / Parasitic infections can be chronic
Why is the host’s immune system forced to remain active? / Due to the chronic infection
What are the results from the host’s immune system remaining active? / Immunosuppression, disruption of normal B-cell and T-cell functions, and hypersensitivity reactions
Working in concert, which several cell types actively participate in the recognition and elimination of parasites from the host? / B and T lymphocytes, natural killer cells, macrophages, other antigen-presenting cells, granulocytes, and mast cells
Which soluble substances also participate in the host’s defenses? / Immunoglobulins, complement, and cytokines
As part of the innate immune defense, what do neutrophils act as? / Phagocytes to destroy both intracellular and extracellular parasites
What does hydrogen peroxide kill? / Extracellular organisms
What do neutrophilic granules destroy? / Ingested organisms
The gamma interferon produced by natural killer cells inhibits what in the parasites? / Replication of the intracellular parasites
How does complement activation provide protection? / Through the production of chemotactic components, opsonization for enhanced phagocytosis, and lysis of extracellular parasites
What is cellular immunity responsible for? / The production of cytokines and chemokines, which enhance the cytotoxic function of effector cells, increase the numbers of immune cells, and attract immune cells to the site of infection
How are many protozoan parasite effectively reduced and eliminated? / By macrophages that are activated by sensitized T cell-generated cytokines such as interferon-gamma and the migration inhibitory factor
The immunoglobulin response to parasites include the formation of which antibodies? / IgM, IgG, IgA, and IgE
In regards to serological response to parasitic and fungal infections, what effects does the specific antibody have? / Antibody can damage protozoa, neutralize parasites by blocking attachment to the host cell, prevent the spread of the parasite, promote complement-mediated lysis, and enhance phagocytosis and destruction of the parasites through antibody-dependent cellular cytotoxicity
What happens with masts cells hen specific antigen-antibody combinations occur? / Mast cells degranulate and release chemotactic factors, histamine, prostaglandins, and other mediators
What is one of the most important chemotactic mediators and what is its function? / Eosinophil chemotactic factor and attracts eosinophils to the infected areas
How can eosinophils destroy helminths? / By degranulation or through antibody-dependent cellular cytotoxicity
What’s the correlation between antibodies to parasites and the prognosis of disease? / Although antibodies are detectable in serum and may be useful guides when diagnosing diseases caused by parasites, they have little or no correlation with the course or prognosis of the disease
What is true about protection from reinfection by a parasite? / Later protection from reinfection by the parasite cannot be predicted on the basis of circulating antibody levels, nor can any other useful information be gained by measuring cellular responses
How are serologic tests used to identify parasites? / Serologic tests can be used to identify parasites present in organs or other deep tissues such as the brain or muscle and that are not recoverable in blood, urine, or feces
Toxoplasmosis results from infection with which parasite? / Toxoplasma gondii
What is Toxoplasma gondii and how does it infect humans? / It is a ubiquitous protozoan parasite that infects humans by ingestion of infective cysts (oocysts)
What are the symptoms of Toxoplasma gondii? / This disease is nearly always asymptomatic or may present with a mild lymphadenopathy
Toxoplasma gondii infection is commonly seen in patients with infection? / AIDS
How long can the cysts of the Toxoplasma gondii remain viable for? / These cysts may remain viable for years, so immunosuppressed patients can exhibit symptoms long after initial infection
What is the greatest concern of the Toxoplasma species? / It can cross the placenta
T. gondii is capable of replicating inside which human cell? / The human macrophage
Why can T. gondii survive indefinitely in the human macrophage? / Because the organism can prevent the fusion of lysosomes with phagosomes
Antibody-coated Toxoplasma organisms can trigger what? / Phagocytosis, which ultimately destroys the organism
What is a fact that further confirms the role played by antibody in controlling the disease with T. gondii? / Immunocompromised patients often experience severe problems with infection with T. gondii
Why does serological testing pay an important role in diagnosing toxoplasmosis? / Because isolation of the organism requires tissue biopsy
What is considered diagnostic with Toxoplasma? / A fourfold increase in the titer of IgG, or high levels of IgM and IgG antibodies
What makes determination of an acute infection difficult for Toxoplasma? / Detectable elevations of IgM may persist for months to years
What assays are available and should be performed when congenital toxoplasmosis is suspected? / Enzyme immunoassay (EIA) for IgM, IgG, or IgA and indirect fluorescent antibody (IFA) assays for IgG
What is the testing method of choice for Toxoplasma, compared to IFA, and why? / EIA is the method of choice, as it is more sensitive, less difficult to perform, and easier to interpret
Are there any useful serological procedures for diagnosing CNS infection in immunocompromised patients? / No
What is the method of choice to detect T. gondii DNA in CSF? / PCR
Why are serum antibody studies not used to identify several protozoa? / Because conventional methods of identification are easier to perform and provide more definitive results
Which five protozoa are identified by microscopic examination of specimens? / Entamoeba histolytica, E. histolytica/dispar, Cryptosporidium parvum, Giardia lamblia, and Trichomonas vaginalis
Feces are tested for which four parasitic infections? / E. histolytica, E. histolytica/dispar, C. parvum, and G. lamblia.
What specimens are tested for T. vaginalis? / Urine or vaginal discharge
What two kits are available for testing E. histolytica, E. histolytica/dispar, C. parvum, and G. lamblia, T. vaginalis? / Direct fluorescent antibody (DFA) and enzyme linked immunosorbent assay (ELISA)
How do the direct fluorescent antibody (DFA) methods work? / Use monoclonal antibody labeled with fluorescein isothiocyanate (FITC) against the parasite’s cell wall to visualize the initial antibody-parasite complex
How do EIA and ELISA methods work? / EIA and ELISA methods employ enzyme conjugated to either antigen or antibody, depending on the assay being performed
PCR techniques have been developed to identify which species of parasites? / Plasmodium, Toxoplasma, Giardia, Trypanosoma, Leishmania, Cryptosporidium, Entamoeba, Microsporidia, Babesia, and Cyclospora
This method has the further advantage of providing the ability to genotype the parasites identified: / PCR
The FDA has recently approved which test for malaria, which can derive results in approximately 15 minutes: / Rapid EIA diagnostic test
This assay allows the differentiation of Plasmodium falciparum from less virulent malarial parasites / EIA assay
Other rapid tests are available for the diagnosis of which parasitic infections: / Cryptosporidium, Giardia, Cyclospora
What is also true of rapid tests? / Are useful in diagnosing foodborne and waterborne illnesses and can help limit the spread of disease
Phagocytosis by which two cells can destroy larval stages of helminths? / Macrophages and neutrophils
Eosinophils and IgE-coated mast cells play an important role in the defense against what? / Tissue parasites such as helminths
Why are intestinal helminth infections relatively simple to diagnose? / Because eggs, adult round worms, and segments of tapeworms are easily recovered from stool specimens
What is true of larvae or embryos of some tapeworm species? / They can exit the host’s intestine and migrate to other tissues
The pathology produced by these wandering parasites depends on what? / The damage caused to the invaded organ or tissue
Why is it difficult to identify the parasite as the causative agent? / Because symptoms are often vague or mimic other disease processes
These kinds of tests can be helpful information when parasites are hard to identify as causative agents: / Serodiagnostic tests
Serodiagnostic tests can be especially helpful in the recognition of what two organisms? / Cysticercosis and Echinococcosis
These are the current serodiagnostic methods for cysticercosis and echinococcosis: / IFA tests; slide, tube, and precipitin tests; complement fixation; particle agglutination tests; and enzyme-linked immunoassays, among others.
Most commercial kit systems are based on what kind of system? / An ELISA system
These are used in immunoblot methods at the Centers for Disease Control and Prevention (CDC) to diagnose cysticercosis, echinococcosis, paragonimiasis, and schistosomiasis: / DNA probes
It is important to consider which factors when choosing a procedure for serologic testing in parasitic infection testing? / Specificity and sensitivity
No external proficiency testing program is currently offered in the area of parasitic diagnostic except for which two parasites? / Toxoplasma and Babesia microti
Why do individual laboratories develop their own methods using antigen purchased from various sources? / Because commercial kits for the diagnosis of some parasitic diseases are not available
What is a problem affecting the choice of a procedure in the course of each individual patient’s infection? / Timing
What is true regarding antibody production against a certain stage in a parasite’s life cycle? / The antibody may not be recovered by a given procedure
Since a particular antibody produced by a parasite’s life cycle can’t be recovered, what must be considered? / The possible formation of cross-reacting antibodies
What is the most important factor for a rapidly growing population of immunocompromised individuals? / The prevalence of immunodeficiency diseases such as AIDS
What is true regarding fungi normally considered nonpathogenic? / They may cause mild to very severe pathology immunocompromised individuals
What are other factors for a rapidly growing population of immunocompromised individual? / Increased use of medications such as broad-spectrum antibiotics for bacterial infections and immunosuppressive agents for treatment of cancer and transplantation patients
Why are mycoses now a serious health problem? / Because of the immunocompromised status of these individuals, a substantial increase in the prevalence of fungal infections has occurred
What is one of the most common opportunistic diseases in patients with AIDS? / Pneumocystis carinii
Why was Pneumocystis carinii now designated as a fungus and not a parasite? / Because it has a greater gene sequence homology with fungi than with parasites
What are fungi? / Eukaryotic cells with nuclei and rigid cell walls
What are the two fundamental structural forms of fungi? / Filamentous molds or yeasts
What are molds composed of? / Hyphae and conidia
Although most fungi are monomorphic, some exhibit what characteristic? / Thermal dimorphism
Dimorphic fungi reproduce as molds at what temperature range? / 25-30 degrees C
Dimorphic fungi reproduce as yeasts at what temperature range? / 35-37 degree C
What is true of the thermal dimorphs that are the etiologic agents of serious systemic mycoses? / They can be life threatening
Of the greater than 80,000 species of fungi that have been identified, how many are considered pathogens? / Less than 400
What is true of those fungi that are etiologic agents of human infection? / They are normally soil saprophytes that have been traumatically introduced into body tissues or accidentally inhaled into the lungs
What types of organisms can cause infection when the host defense is deficient for only a brief period? / Endogenous
How are mycoses usually clinically classified? / Superficial, cutaneous, subcutaneous, and systemic