Immunodiagnostics Flashcards
(19 cards)
What are the educational objectives of immunodiagnostics?
- Understand how humoral and cell mediated immune responses can be measured
- Understand how antibodies can be used to detect pathogens
- Discuss the clinical utility of immunodiagnostic assays
- Interpret infectious serology results to establish the timing of an infection
Educational objectives provide a framework for understanding the importance of immunodiagnostics in clinical practice.
What is the primary challenge in detecting infectious agents?
Difficult to culture bacteria, viruses, fungi or parasites
Culturing these agents can be time-consuming and may not always be successful.
What are the three key questions addressed by immunodiagnostics regarding infection?
- Is the patient infected?
- Did infection occur recently?
- Is the patient immune to infection?
These questions help in diagnosing and understanding the patient’s immune status.
What does an immune response against self antigens indicate?
Autoimmunity
Autoimmunity refers to the body’s immune system attacking its own cells.
What does an immune response against innocuous environmental antigens indicate?
Allergy
Allergies occur when the immune system mistakenly identifies harmless substances as threats.
What is the significance of histocompatibility in transfusion and transplantation?
Determines if the donor and recipient are compatible
Histocompatibility reduces the risk of rejection in transplant procedures.
How can we measure antigen and the immune response?
- Detection of infectious agents (Antigen)
- Detection of immune response (Antibody or T cell response)
These measurements are essential for diagnosing infections and immune conditions.
What are some methods for measuring antigen and antibody?
- Agglutination
- Immunofluorescence
- Neutralization
- Enzyme immunoassay
- Immunochromatographic test
Each method has specific applications in detecting antigens or antibodies.
What is the purpose of direct immunofluorescence?
Detection of antigen
Direct immunofluorescence directly labels antigens in a sample for visualization.
What is the purpose of indirect immunofluorescence?
Detection of antibody
Indirect immunofluorescence uses a secondary antibody to detect antibodies bound to antigens.
What does a Rapid Plasma Reagin (RPR) test detect?
Non-treponemal tests for antibodies against damaged cell wall components
RPR tests are commonly used to screen for syphilis.
What does an IgM positive and IgG negative result indicate?
Recent infection
This combination suggests that the infection is acute.
What does IgG avidity refer to?
Accumulated strength of multiple affinities
Avidity is a measure of the overall strength of binding between an antibody and its antigen.
What is the typical time frame for IgM to appear after an infection?
10-14 days
IgM is often the first antibody produced in response to an infection.
What does a high titre of anti-dsDNA antibodies indicate?
> 8 IU/mL = high titres largely confined to cases of SLE
This measurement is significant for diagnosing Systemic Lupus Erythematosus (SLE).
What is the role of the QuantiFERON-TB Gold In-Tube assay?
Measures interferon-gamma release in response to TB antigens
This test is used for diagnosing latent tuberculosis infection.
What does a wheal-and-flare reaction indicate in skin prick testing?
Type I hypersensitivity: IgE-mediated
This reaction is a common response to allergens in allergy testing.
What is a characteristic of Type IV hypersensitivity?
Cell-mediated response
This type of hypersensitivity is delayed and involves T cells.
What is the significance of class switching in antibodies?
Allows the immune system to produce different classes of antibodies (IgM, IgG, IgA, etc.)
Class switching enables the immune response to adapt to different pathogens.
