Biochemistry
1 questionsWhat is the molecular mass of Immunoglobulin G (IgG) in kilodaltons (kDa)?
NEET-PG 2015 - Biochemistry NEET-PG Practice Questions and MCQs
Question 591: What is the molecular mass of Immunoglobulin G (IgG) in kilodaltons (kDa)?
- A. 150 (Correct Answer)
- B. 400
- C. 1000
- D. 1500
Explanation: **\*Correct Option: 150 kDa\*** - **Immunoglobulin G (IgG)** is the most abundant antibody in human serum and has a characteristic molecular mass of approximately **150 kDa**. - This mass is attributed to its structure, comprising two identical **heavy chains** (~50 kDa each) and two identical **light chains** (~25 kDa each). - IgG represents about **75-80% of total serum immunoglobulins** and is the main antibody involved in secondary immune responses. *Incorrect Option: 400 kDa* - A molecular mass of **400 kDa** is significantly higher than that of a monomeric IgG molecule. - This mass is closer to **IgM pentamers** (~900 kDa) or large protein complexes, but still does not match any standard immunoglobulin structure. *Incorrect Option: 1000 kDa* - A molecular mass of **1000 kDa (1 MDa)** is far too large for a single IgG molecule. - This weight typically corresponds to very large macromolecular structures or aggregates, such as **ribosomes** or large enzyme complexes. *Incorrect Option: 1500 kDa* - A molecular mass of **1500 kDa (1.5 MDa)** is extremely large for an individual antibody. - Such a mass would be characteristic of very large protein assemblies, viral capsids, or cellular components, not a soluble antibody.
Internal Medicine
1 questionsWhich condition is not associated with complement deficiency?
NEET-PG 2015 - Internal Medicine NEET-PG Practice Questions and MCQs
Question 591: Which condition is not associated with complement deficiency?
- A. SLE
- B. PNH
- C. Membranous nephritis (Correct Answer)
- D. Hereditary angioedema
Explanation: Membranous nephritis - Membranous nephritis is associated with immune complex deposition rather than complement deficiencies. [1] - The disease is characterized by thickening of the glomerular basement membrane without significant complement involvement. [1] PNH - Paroxysmal nocturnal hemoglobinuria (PNH) is due to a defect in the GPI-anchor leading to complement-mediated hemolysis. - Complement activation plays a critical role in the destruction of red blood cells in this condition. Hereditary angioedema - Hereditary angioedema is caused by deficiencies in C1 inhibitor, leading to uncontrolled activation of complement. - This results in edema episodes, directly linked to complement pathway dysregulation. SLE - Systemic lupus erythematosus (SLE) involves complement consumption due to autoantibody formation against nuclear antigens. - The disease often presents with hypocomplementemia, indicating complement system involvement.
Microbiology
7 questionsIn the context of diagnosing syphilis, which of the following is an example of a precipitation test?
Haptens are immunogenic when they covalently bind to which type of carrier?
Which human IgG subclass has the highest serum concentration?
Which of the following does not stimulate active immunity?
Which of the following is a specific feature of acquired immunity?
Lattice phenomenon is seen in which of the following?
To which part of an antigen do monoclonal antibodies specifically bind?
NEET-PG 2015 - Microbiology NEET-PG Practice Questions and MCQs
Question 591: In the context of diagnosing syphilis, which of the following is an example of a precipitation test?
- A. Rose waaler test
- B. Widal test
- C. Latex agglutination
- D. Kahn test (Correct Answer)
Explanation: ***Kahn test*** - The Kahn test is a **flocculation** or **precipitation** test used for diagnosing syphilis. - It detects **reagin antibodies** in the patient's serum that react with a non-treponemal antigen (cardiolipin antigen). *Rose waaler test* - The Rose Waaler test is an **agglutination test** used to detect **rheumatoid factor** in patients with rheumatoid arthritis, not syphilis. - It involves sheep red blood cells sensitized with rabbit anti-sheep erythrocyte antibody. *Widal test* - The Widal test is an **agglutination test** used for the diagnosis of **typhoid fever**, detecting antibodies against *Salmonella* O and H antigens. - It is not used for the diagnosis of syphilis. *Latex agglutination* - Latex agglutination is a general type of **agglutination test** where antigen or antibody is coated onto latex particles. - While used in various diagnoses, it is not a specific precipitation test for syphilis in the context of classic methods like the Kahn test.
Question 592: Haptens are immunogenic when they covalently bind to which type of carrier?
- A. Lipid carrier
- B. Polysaccharide carrier
- C. Protein carrier (Correct Answer)
- D. None of the above carrier
Explanation: ***Protein carrier*** - Haptens are small molecules that are **antigenic** but not **immunogenic** on their own; they acquire immunogenicity when covalently bound to a larger carrier molecule. - **Proteins** are highly effective carriers because their complex structures and multiple epitopes can induce strong T-cell help, which is crucial for a robust antibody response against the hapten. *Lipid carrier* - While some lipids can be antigenic (e.g., glycolipids), they generally do not serve as effective carriers for haptens to induce a strong adaptive immune response, especially T-cell-dependent responses. - **Lipids** are less likely to be processed and presented by MHC molecules in a way that generates potent helper T-cell activation. *Polysaccharide carrier* - Some polysaccharides can be immunogenic themselves (e.g., bacterial capsular polysaccharides) and can induce T-cell-independent antibody responses. - However, for haptens to become immunogenic and induce a **T-cell-dependent antibody response**, a protein carrier is typically required. *None of the above carrier* - This option is incorrect because haptens do require a carrier to become immunogenic, and specific types of carriers are more effective than others. - The type of carrier chosen significantly impacts the **strength and nature of the immune response** to the hapten.
Question 593: Which human IgG subclass has the highest serum concentration?
- A. IgG1 (Correct Answer)
- B. IgG2
- C. IgG3
- D. IgG4
Explanation: ***IgG1*** - **IgG1** constitutes approximately **60-70%** of the total IgG in human serum, making it the most abundant subclass. - Its high concentration reflects its crucial role in **neutralizing toxins**, agglutinating viruses, and opsonizing bacteria for phagocytosis. *IgG2* - **IgG2** makes up about **20-30%** of total IgG and is primarily important in protecting against **polysaccharide-encapsulated bacteria**. - While significant, its serum concentration is notably lower than that of IgG1. *IgG3* - **IgG3** is the least abundant IgG subclass, accounting for only **5-8%** of total IgG, and is characterized by a shorter half-life. - Despite its low concentration, it is highly efficient in activating the **complement system** due to its flexible hinge region. *IgG4* - **IgG4** comprises approximately **3-6%** of total IgG and is unique for its ability to undergo **Fab arm exchange**, leading to bispecific antibodies. - It does not activate complement and is often associated with allergy and protection against parasitic infections, but its concentration is significantly less than IgG1.
Question 594: Which of the following does not stimulate active immunity?
- A. Clinical infection
- B. Vaccination
- C. Transplacental antibody transfer in newborn (Correct Answer)
- D. Subclinical infection
Explanation: ***Transplacental antibody transfer in newborn*** - This is a form of **passive immunity**, where pre-formed **antibodies from the mother** are transferred to the newborn, providing immediate but temporary protection. - It does not involve the newborn's own immune system generating an immune response or creating **memory cells**. *Subclinical infection* - Even without overt symptoms, a **natural infection** exposes the immune system to pathogens, triggering an active immune response and generating **memory cells**. - This leads to **long-term immunity** against future exposures to the same pathogen. *Clinical infection* - A **symptomatic natural infection** involves the immune system actively responding to the pathogen, producing antibodies and **memory cells**. - This process is the basis of **naturally acquired active immunity** and provides durable protection. *Vaccination* - Vaccines contain weakened or inactive forms of pathogens, or their components, which stimulate the immune system to produce **antibodies** and **memory cells** without causing disease. - This is an example of **artificially acquired active immunity**, providing long-lasting protection.
Question 595: Which of the following is a specific feature of acquired immunity?
- A. Immunological memory (Correct Answer)
- B. Affected by genetic makeup
- C. No antigen exposure
- D. Immediate response
Explanation: ***Immunological memory*** - A key characteristic of **acquired immunity** is the ability to "remember" previous encounters with specific pathogens. - This memory leads to a more rapid and robust immune response upon subsequent exposure to the same pathogen. - This is the **defining feature** that distinguishes acquired immunity from innate immunity. *Affected by genetic makeup* - While genetic makeup can influence the *efficiency* of the acquired immune system, it is not a **specific feature** that distinguishes it from innate immunity. - **Both innate and acquired immunity** are affected by genetic factors, determining baseline resistance and immune response capability. *No antigen exposure* - **Acquired immunity** is specifically characterized by its *dependence* on antigen exposure to develop specific responses. - The phrase "no antigen exposure" describes how the **innate immune system** functions, providing immediate, non-specific protection without prior contact with a pathogen. *Immediate response* - **Innate immunity** provides an immediate, non-specific response to pathogens. - **Acquired immunity** takes time to develop (days to weeks) after initial antigen exposure, but provides a faster response upon re-exposure due to immunological memory.
Question 596: Lattice phenomenon is seen in which of the following?
- A. Complement fixation test
- B. Precipitation test (Correct Answer)
- C. None of the options
- D. Neutralization reaction
Explanation: ***Precipitation test*** - The **lattice phenomenon** describes the formation of an interconnected network of antigen-antibody complexes, which is essential for visible precipitation to occur. - This phenomenon dictates that optimal precipitation requires a specific **antigen-to-antibody ratio**; an excess of either can lead to false-negative results due to soluble immune complexes (prozone or postzone effects). *Complement fixation test* - This test relies on the **binding of complement** to antigen-antibody complexes, leading to the lysis of indicator red blood cells if complement is not fixed. - It is a **two-stage test** that measures the consumption of complement, not the direct observation of a lattice. *None of the options* - This option is incorrect because the **precipitation test** clearly demonstrates the lattice phenomenon. - The formation of a visible precipitate is a direct result of antigen-antibody lattice formation. *Neutralization reaction* - Neutralization involves antibodies binding to toxins or viruses, **blocking their biological activity** rather than forming a visible precipitate. - It is a **functional assay** that measures the ability of antibodies to inhibit harmful effects, not the formation of large immune complexes.
Question 597: To which part of an antigen do monoclonal antibodies specifically bind?
- A. None of the options
- B. Specific epitope on the antigen (Correct Answer)
- C. Both the epitope and the paratope
- D. Part of the antibody that binds to the epitope
Explanation: ***Specific epitope on the antigen*** - Monoclonal antibodies are designed to recognize and bind to a **unique, specific region** on an antigen, known as an **epitope**. - This high specificity is crucial for their clinical applications, such as targeted therapies and diagnostic tests. *Both the epitope and the paratope* - The **epitope** is the part of the antigen, while the **paratope** is the part of the antibody that binds to the epitope. - An antibody binds to an epitope, not to both itself and its own binding site. *None of the options* - This option is incorrect because there is a correct answer among the choices provided, which accurately describes the binding site of monoclonal antibodies. *Part of the antibody that binds to the epitope* - This describes the **paratope**, which is the antigen-binding site on the antibody, not the part of the antigen to which the antibody binds. - The question specifically asks about the part of the antigen.
Obstetrics and Gynecology
1 questionsIgM appears in fetus at what gestational age -
NEET-PG 2015 - Obstetrics and Gynecology NEET-PG Practice Questions and MCQs
Question 591: IgM appears in fetus at what gestational age -
- A. 10 weeks
- B. 20 weeks (Correct Answer)
- C. 30 weeks
- D. at birth
Explanation: ***20 weeks*** - The fetal immune system begins to develop around **20 weeks of gestation**, at which point the fetus starts producing its own **IgM antibodies**. - **IgM** is the first antibody isotype produced by the developing fetal **B lymphocytes** and is important for early immune responses. *10 weeks* - While some components of the immune system may start to differentiate earlier, **IgM production** at a functional level is not yet established at **10 weeks of gestation**. - At this early stage, the fetal immune system is still primarily in its **developmental phase**, with major organogenesis occurring. *30 weeks* - By **30 weeks**, the fetus has already been producing IgM for several weeks, and the immune system is more mature, capable of a more robust **antibody response**. - While **IgG** levels are significantly increasing due to maternal transfer at this stage, **IgM production** began earlier. *at birth* - At birth, a neonate has circulating **IgM antibodies**, which are indicative of prior fetal immune activation and are measurable in umbilical cord blood. - However, the initial production of **fetal IgM** occurs much earlier in gestation, not at the time of birth.