Immunology Exam Flashcards
What are the stages of progression for HIV infection
Acute HIV infection
Clinical latency stage
Symptomatic HIV infection
Acquired Immunodeficiency Syndrome (AIDS)
Explain the Acute HIV infection stage
Occurs within a few weeks after initial exposure to HIV.
Virus replicates rapidly resulting in a high viral load.
Flu-like symptoms; fever, fatigue, sore throat, rash and swollen lymph nodes (some individuals may have mild / no symptoms)
Explain Clinical Latency stage for HIV
(Also known as Chronic or Asymptomatic stage)
Phase can last for several years
virus continues to replicate but at a slower rate
virus is active and can be transmitted
Most do not experience significant symptoms
Explain Symptomatic stage for HIV infection
Immune system gradually becomes weakened
Symptoms such as persistent fever, weight loss, chronic diarrhea and infections begin.
Infections take advantage of weakened immune system = pneumonia, TB, cancer
Explain AIDS stage
Acquired immunodeficiency Syndrome
Most advanced stage of HIV
Occurs when immune system is severely damaged and CD4 count drops below 200 cells per microliter
At this stage, individuals are highly susceptible to opportunistic infections which can be life-threatening
Describe Viral load monitoring for HIV and its importance
Measures the amount of HIV RNA in a person’s blood and is a crucial component of HIV management
Viral load helps determine how effectively antiretroviral therapy (ART) is suppressing the virus and allows clinicians to monitor progression
Describe a method of viral load monitoring for HIV
Polymerase Chain Reaction (PCR): PCR is the most widely used method for HIV viral load monitoring. It amplifies the viral RNA present in a blood sample to detect and quantify the amount of HIV in the bloodstream.
Explain PCR viral load process for HIV
7 Stages
plasma / serum sample is collected
RNA is extracted and isolated from blood using laboratory techniques; this involves breaking open the virus particles
Since HIV is an RNA virus, the viral RNA needs to be converted into cDNA before PCR amplification can occur; this step is called reverse transcriptase.
The cDNA generated from reverse transcriptase serves as a template for PCR amplification
PCR reaction mixture contains cDNA, primers, polymerase enzyme and other necessary components.
Each PCR cycle doubles the amount of DNA, leading to exponential amplification of the target region. After multiple cycles, the target DNA segment (in this case, the HIV viral RNA) is amplified to a detectable level.
In the case of HIV viral load monitoring, fluorescence-based detection techniques are commonly employed. Fluorescent probes that specifically bind to the amplified HIV DNA are used to measure the level of fluorescence, which is proportional to the amount of viral genetic material present in the sample
What are the different phases and periods for HIV infection
(WAS)
Window phase
Acute phase
Seroconversion period
Describe the Window phase for HIV in the context of antibodies
This is the time between HIV infection and the production of detectable HIV antibodies. During this phase, which can last several weeks, standard antibody tests may yield negative results despite the presence of the virus.
However, specialized tests like nucleic acid testing (NAT) can detect the virus directly during this period.
Describe the Acute phase of HIV in the context of antibodies
The acute phase occurs immediately after the window period and typically lasts a few weeks.
high viral load, rapid viral replication, and flu-like symptoms.
Antibodies against HIV start to develop during this phase, leading to seroconversion.
Describe the Seroconversion Period for HIV
Seroconversion refers to the development of detectable HIV antibodies in the blood.
It usually occurs within three to twelve weeks after infection, with an average time of around 25 days.
During seroconversion, individuals may experience symptoms similar to the flu or may remain asymptomatic. Once seroconversion takes place, standard HIV antibody tests become positive, indicating HIV infection.
What is the one distinctive HIV Antigen?
p24 viral protein
p24 viral protein relevance to HIV
Useful in diagnosing primary HIV infection.
High levels of p24 are present in the blood serum of newly infected individuals during the short period between infection and seroconversion
Antibodies to p24 are produced during seroconversion
rendering the p24 antigen undetectable after seroconversion in most cases. Therefore, p24 antigen assays are not reliable for diagnosing HIV infection after its very earliest stages
Define autoimmune disease and what are the outcomes
Autoimmune disease refers to a condition in which the immune system, which normally protects the body against harmful substances, mistakenly attacks healthy cells and tissues.
Instead of targeting foreign invaders like bacteria or viruses, the immune system produces autoantibodies that attack the body’s own cells, tissues, and organs.
This immune response leads to inflammation, tissue damage, and various symptoms specific to the affected organ or system.
Discuss the challenges in diagnosis when it comes to Autoimmune diseases
Vague and overlapping symptoms
Many autoimmune diseases share similar symptoms eg. fatigue, joint pain and inflammation. These symptoms can be nonspecific and may mimic other conditions making it difficult to differentiate between autoimmune diseases and other underlying causes
Lack of specific diagnostic tests
While certain autoantibodies can be detected in some autoimmune diseases, there is often a lack of specific tests for many conditions. Diagnosis usually relies on a combination of clinical evaluation, medical history, physical examination and lab tests.
Delayed onset and variable progression
Autoimmune diseases can have a delayed onset, with symptoms appearing gradually over time. Additionally the progression of these diseases can vary greatly among individuals making it challenging to identify the disease at an early stage
What is coeliacs disease
Coeliac disease is an autoimmune disease triggered by the ingestion of gluten, a protein found in wheat, barley, and rye.
When individuals with coeliac disease consume gluten, it leads to an immune response that damages the lining of the small intestine, resulting in various symptoms and potential long-term complications.
Symptoms of Coeliacs
MSJD
Malabsorption
Skin problems; itchy rash, blistering lesions
Joint and muscle pain
Digestive Issues; Abdominal pain, bloating, diarrhea, constipation, and nausea.
Discuss the diagnostic strategy for Coeliacs disease
The first step is to assess the patient’s symptoms and medical history.
Coeliac disease is often suspected in individuals who experience symptoms such as chronic diarrhea, abdominal pain, bloating, weight loss, fatigue, or deficiencies in certain nutrients like iron or vitamin D.
Serology testing
The next step involves blood tests to detect specific antibodies associated with coeliac disease. The primary antibodies measured are tissue transglutaminase antibodies (tTG-IgA). Elevated levels of tTG-IgA suggest a high likelihood of coeliac disease. Total IgA levels may also be measured to identify potential IgA deficiency, which could affect the reliability of the tTG-IgA test.
Intestinal Biopsy
The definitive diagnosis of coeliac disease usually requires an intestinal biopsy. This involves taking small samples of tissue from the small intestine, typically through an endoscopy procedure. The samples are then examined under a microscope to look for characteristic changes in the intestinal lining, such as villous atrophy, increased intraepithelial lymphocytes, and crypt hyperplasia.
Genetic Testing
Genetic testing is not used to diagnose coeliac disease directly but can be helpful in certain cases. The presence of specific human leukocyte antigen (HLA) genes, such as HLA-DQ2 and HLA-DQ8, is strongly associated with coeliac disease. However, it’s important to note that not all individuals with these genes develop coeliac disease, and their absence does not rule out the condition.
Coeliacs disease diagnosis summary
It’s important to note that for accurate results, patients should be on a gluten-containing diet (containing gluten from wheat, barley, and rye) prior to serology testing and intestinal biopsy. A gluten-free diet can lead to false-negative results and should only be initiated after the diagnostic process is complete.
Overall, the diagnostic strategy for coeliac disease involves a combination of clinical evaluation, serology testing, genetic testing, and intestinal biopsy to establish a definitive diagnosis.
What is the ANA test
ANA test also known as the antinuclear antibody test is used to detect the presence of antinuclear antibodies in the blood.
These antibodies attack the body’s own cell nuclei and can be associated with various autoimmune diseases.
Principle of ANA
Indirect Immunofluorescence (IIF)
In this technique, patient serum is exposed to a substrate (typically human epithelial cells eg. hep-2000 cells) containing a mixture of different antigens in the cell nuclei.
If ANA is present in the patient’s serum, it will bind to these antigens.
After the serum is incubated on a slide containing fixed cells, it is washed to remove any unbound antibodies.
After washing, a fluorescently labelled secondary antibody is added which binds to the ANA if present.
When exposed to specific wavelengths the fluorescence can be visualized as bright green apple staining under a fluorescent microscope.
Common patterns include; homogenous, speckled, nucleolar and centromere
After the detection of ANA, titers are carried out until a weak fluorescent grade of 1 is detected for reporting.
Purpose of ANA
Diagnosis of autoimmune diseases
ANA test is primarily used to help diagnose autoimmune diseases, such as systemic lupus erythematosus (SLE), Sjögren’s syndrome, rheumatoid arthritis, and systemic sclerosis.
Disease monitoring
For individuals who have already been diagnosed with an autoimmune disease, the ANA test may be used to monitor the progression of the disease and the effectiveness of treatment.
Differential diagnosis
The ANA test can assist in distinguishing between autoimmune diseases and other conditions that may have similar symptoms. It is not a definitive diagnostic tool on its own, but it can aid in the overall diagnostic process when combined with other clinical and laboratory findings.
Research purposes
The ANA test is also used in research studies to investigate the mechanisms and patterns of autoimmune diseases, as well as to explore potential new treatments and therapies.
Limitation of ANA test
ANA test result indicates the presence of antinuclear antibodies, it does not provide a definitive diagnosis of a specific autoimmune disease.
Further evaluation, including a comprehensive medical history, physical examination, additional laboratory tests, and consultation with a healthcare professional, is necessary for accurate diagnosis and appropriate treatment.
What is the ENA test
An extractable nuclear antigen test is a laboratory test used to detect specific antibodies against extractable nuclear antigens in the blood.
Extractable nuclear antigens are proteins that are found in the cell nucleus and can be associated with various autoimmune diseases.
The ENA test is a more specific and targeted test compared to the ANA test.
