An anti-idiotypic antibody with fluorescent tag was used for detection of immune cells in tissue sections from a healthy individual specifically by cell surface labeling. Which of the following will have the highest chances of getting detected?
Mature B cells in spleen
Understanding Anti-Idiotypic Antibodies
An anti-idiotypic antibody is a type of antibody that specifically binds to the unique antigen-binding site (also called the idiotype) of another antibody. In this question, an anti-idiotypic antibody with a fluorescent tag is used for cell surface labeling of immune cells in tissue sections. This means the antibody is designed to stick to a specific molecule present on the surface of certain immune cells.
When detecting immune cells via cell surface labeling using an antibody, you are looking for cells that express the target molecule on their outer membrane at a detectable level.
Cell Surface Detection with Anti-Idiotypic Antibodies
Consider what kind of immune cell would likely have a surface molecule that could be targeted by an anti-idiotypic antibody. Antibodies themselves, including the B cell receptor (BCR), are immunoglobulins that have unique variable regions forming their idiotype. The BCR is found on the surface of B cells and is essentially a membrane-bound antibody molecule.
An anti-idiotypic antibody can be generated against the idiotype of a specific antibody or, in this context, the idiotype of the BCR expressed by B cells. Binding of the fluorescently tagged anti-idiotypic antibody to the BCR on the cell surface would allow for the detection and localization of these cells in tissue sections.
Analyzing the Immune Cell Options
Let's examine the options provided:
- Macrophages: These are phagocytic cells of the myeloid lineage. They play a role in antigen presentation but do not express surface immunoglobulins (BCRs) as their primary surface markers for antigen recognition.
- Mature B cells: These lymphocytes express high levels of surface immunoglobulin, specifically the B cell receptor (BCR). The BCR has a unique idiotype. An anti-idiotypic antibody targeting the idiotype of the BCR would bind to the surface of mature B cells, making them highly detectable via surface labeling. Mature B cells are abundant in secondary lymphoid organs like the spleen and lymph nodes.
- Terminally differentiated plasma cells: These cells are derived from B cells and are primarily responsible for secreting large quantities of antibodies. While they originate from B cells, terminally differentiated plasma cells have significantly reduced or absent surface expression of BCRs. Therefore, they are not easily detected by surface labeling using an anti-idiotypic antibody targeting the BCR idiotype.
- Eosinophils: These are granulocytes involved in allergic reactions and defense against parasites. They are part of the innate immune system and do not express surface immunoglobulins or BCRs.
Highest Chances of Detection
Given that the detection method uses an anti-idiotypic antibody for cell surface labeling, the cell type that expresses a significant amount of surface immunoglobulin (which carries an idiotype) is the most likely candidate for detection. Mature B cells fit this description perfectly due to their high surface expression of BCRs. While B cells are found in both lymph nodes and the spleen, the question asks which option has the highest chances of getting detected. Mature B cells in the spleen represent a major population readily detectable by this method.
Therefore, mature B cells in the spleen will have the highest chances of getting detected using a fluorescently tagged anti-idiotypic antibody for cell surface labeling.
Important Questions from Histochemical and Immunotechniques
For a given immunological application [column X], select the type of antibody [column Y] that should be used:
Choose the option with correct matches between terms of Columns X and Y.Column X Column Y A Bacterial agglutination (i) Only monoclonal B Western blotting (ii) Only polyclonal C Detection of a cytokine using a solid phase ELISA (iii) Either monoclonal or
polyclonalD Diagnostic tissue typing In the enzyme-linked antibody used in ELISA, the interaction between the enzyme and antibody is stabilized by
A researcher raised antibodies against sheep red blood cells (SRBCs) and purified the IgG fraction. Some of the IgG antibodies were then subjected to enzymatic digestion to have Fab, Fc and F(ab’)2 fractions. He placed each preparation in a separate tube ( 1 to 3), labeled the three tubes to indicate their contents, and incubated them on ice. After a while he noticed that the label on two of the tubes (1 and 2) had gotten erased. He did a test for tube 1 and found that the preparation in the tube agglutinated SRBCs but did not lyse them in presence of complement. Which preparation was in tube 1?
To investigate the relationship between microtubules and centrioles in fixed HeLa cells using an epifluorescence microscope, a researcher plans to conduct immunostaining using antibodies against tubulin and centrin (centriolar protein). After the incubation with the primary antibodies and wash, she/he plans to use secondary antibodies that bind to the primary antibodies. Below is a list of secondary antibodies carrying various fluorophores (dyes) available to the researcher.
A. Alexa 568
B. FITC
C. Alexa 488
D. Alexa 647
Select the correct combinations of the appropriate dyes that the researcher would typically utilize to observe co‐localization in an epifluorescence microscope?
PBMCs from the blood collected from a tuberculosis (TB) patient were given to four lab technicians to perform ELISPOT assay for interferon γ (IFNγ). While all steps recommended for ELISPOT were followed, the first step was performed differently by the four lab technicians, as detailed below.
A Lab technician 1 coated each well with 250.000 formaldehyde- treated cells and stimulated the cells with TB-specific antigen.
B. Lab technician 2 coated each well with 250,000 cells and did not stimulate the cells with TB-specific antigen.
C. Lab technician 3 depleted T cells from PBMCs completely, coated the wells with monocyte-enriched PBMCs, and stimulated them with TB-specific antigen.
D. Lab technician 4 coated each well with 250.000 cells and stimulated the cells with TB-specific antigens.
Which of the lab technicians assays will yield a correct ELISPOT result for interferon γ?
