NEET-PG 2013 Practice Questions

Q: The BEINGS Model of disease causation does not include which of the following factors?

Spiritual factors. ***Spiritual factors*** - The **BEINGS model** does not include \"Spiritual factors\" as one of its components. - The BEINGS acronym stands for: **B**iological, **E**nvironmental, **I**mmunological, **N**utritional, **G**enetic, and **S**ocial factors. - While spirituality can influence health outcomes, it is not a formal component of this epidemiological model. *Religious factors* - Religious factors, like spiritual factors, are also not explicitly part of the BEINGS model. - However, religious practices and beliefs may be considered as part of **social factors** (the \"S\" in BEINGS) in some contexts. - This option is less clearly excluded than spiritual factors. *Social factors* - The \"**S**\" in BEINGS specifically stands for **Social factors**, not spiritual factors. - Social factors include community networks, socioeconomic status, cultural practices, and social support systems. - These are well-established determinants of health and disease causation. *Nutritional factors* - The \"**N**\" in BEINGS stands for **Nutritional factors**. - Nutrition plays a critical role in disease causation, affecting immunity, growth, and susceptibility to various diseases. - Deficiencies or excesses in nutrition can lead to a wide range of health problems.

Q: Which of the following is a superantigen ?

TSST. ***TSST*** - **Toxic Shock Syndrome Toxin-1 (TSST-1)** is a classic example of a superantigen produced by *Staphylococcus aureus*. - Superantigens **bind directly to MHC class II molecules and T-cell receptors (TCRs)** outside of the antigen-binding groove, leading to non-specific activation of a large percentage of T cells and a massive release of cytokines. *Cholera toxin* - **Cholera toxin** is an exotoxin produced by *Vibrio cholerae* that causes massive fluid secretion in the intestine by **activating adenylate cyclase** in enterocytes. - It functions by **ADP-ribosylating the Gs alpha subunit**, leading to constitutive activation of cyclic AMP production, but it is not a superantigen. *Diphtheria toxin* - **Diphtheria toxin**, produced by *Corynebacterium diphtheriae*, inhibits protein synthesis in eukaryotic cells by **ADP-ribosylating elongation factor-2 (EF-2)**. - This action leads to cell death and the characteristic pseudomembrane formation in diphtheria, but it does not act as a superantigen. *Vero-cytoxin* - **Vero-cytoxin** (also known as Shiga toxin or Shiga-like toxin) is produced by *E. coli* O157:H7 and other Shiga toxin-producing *E. coli* (STEC). - It inhibits protein synthesis by **cleaving ribosomal RNA**, primarily causing damage to intestinal cells and renal endothelial cells, but it is not a superantigen.

Q: Rosette formation with sheep RBCs (SRBCs) indicates functioning of -

T-cells. ***T-cells*** - **T-cells** possess specific receptors, like **CD2** on their surface, that can bind to ligands on sheep red blood cells (SRBCs). - This binding leads to the formation of characteristic **rosettes**, where SRBCs cluster around the T-lymphocytes, indicating functional T-cells. *B-cells* - **B-cells** primarily function in **humoral immunity** by producing antibodies and do not typically form rosettes with sheep RBCs. - While B-cells have surface receptors, they are not CD2 and thus do not facilitate this specific type of rosette formation. *Neutrophils* - **Neutrophils** are **phagocytic cells** involved in innate immunity, primarily combating bacterial and fungal infections. - They lack the specific surface receptors (like CD2) required to form rosettes with sheep RBCs. *Monocytes* - **Monocytes** are precursors to macrophages and dendritic cells, involved in phagocytosis and antigen presentation. - They do not possess the necessary surface markers to form rosettes with sheep RBCs.

Q: Cytolytic activity of membrane attack complex is modulated by ?

Factor S (vitronectin). ***Correct Option: Factor S (vitronectin)*** - Vitronectin (S-protein) is a **plasma protein** that directly modulates the **cytolytic activity of the membrane attack complex (MAC)**. - It binds to the **C5b-7 complex** in the fluid phase, preventing its insertion into target cell membranes and thereby blocking the formation of the complete, functional MAC. - By inhibiting membrane insertion of C5b-7, vitronectin prevents the subsequent binding of **C8 and C9**, which are essential for the cytolytic pore formation. - This is a **direct modulation** of MAC's cytolytic activity at the MAC assembly stage. *Incorrect Option: Factor H* - Factor H is a regulatory protein that controls the **alternative pathway** of complement activation by promoting degradation of **C3b**. - By degrading C3b, Factor H prevents formation of **C5 convertase**, thereby reducing downstream MAC formation. - However, Factor H acts **early in the complement cascade** and does not directly modulate the cytolytic activity of already-formed MAC components. - Its effect is on **preventing MAC formation**, not on modulating MAC's cytolytic function itself. *Incorrect Option: Factor I* - Factor I is a **serine protease** that cleaves and inactivates C3b and C4b, requiring cofactors like Factor H or C4bp. - Like Factor H, it regulates complement activation **upstream** of MAC formation. - It does not directly interact with or modulate the cytolytic activity of the MAC. *Incorrect Option: Factor B* - Factor B is a component of the **alternative pathway C3 convertase** (C3bBb). - It **promotes complement activation** rather than modulating MAC's cytolytic activity. - Factor B functions early in the cascade and has no direct role in regulating MAC function.

Q: What is the primary use of the Hybridoma technique?

Monoclonal antibodies. ***Monoclonal antibodies*** - The **hybridoma technique** is primarily used to produce **monoclonal antibodies (MAbs)**, which are highly specific antibodies derived from a single B-cell clone. - These antibodies recognize a **single epitope** on an antigen, providing exceptional specificity and uniformity. - The technique involves **fusing a B-lymphocyte** (antibody-producing cell) with a **myeloma cell** (immortal cancer cell) to create a hybridoma that continuously produces identical antibodies. - This is the **gold standard** for producing large quantities of identical, highly specific antibodies for diagnostic and therapeutic use. *Specific antibodies* - While monoclonal antibodies are indeed specific, this term is **too vague** and could refer to any antibody with specificity, including polyclonal antibodies. - **Polyclonal antibodies** are also specific but are produced through conventional immunization, not the hybridoma technique. - The defining characteristic of the hybridoma technique is that it produces **monoclonal** (single clone) antibodies, not just "specific" ones. *Antigen* - An **antigen** is a molecule that elicits an immune response and is used to immunize animals during antibody production. - However, antigens are the **input** for antibody production, not the **product** of the hybridoma technique. *Cytokines* - **Cytokines** are signaling molecules involved in immune cell communication and regulation. - They are not produced by the hybridoma technique, which is specifically designed for **antibody production**.

Q: Which immunoglobulin is primarily secreted by the intestine?

IgA. **IgA** - **Secretory IgA** is the dominant immunoglobulin in mucosal secretions, including those of the intestine. - It plays a crucial role in providing **local immunity** by preventing microbial adherence and neutralizing toxins on mucosal surfaces. *IgG* - **IgG** is the most abundant immunoglobulin in serum and plays a major role in systemic immunity, including opsonization and complement activation. - While some IgG is found in secretions, it is not the primary immunoglobulin secreted by the intestine. *IgM* - **IgM** is a pentameric immunoglobulin, primarily found in blood and lymph, where it is very effective in activating the complement system and agglutinating antigens. - Although it can be found at mucosal surfaces in small amounts, it is not the principal secreted antibody in the intestine. *IgD* - **IgD** is primarily found on the surface of naive B lymphocytes, where it functions as a B cell receptor. - Its role in secreted form is minimal, and it is not significantly secreted into the intestine or other bodily fluids.

Q: ABO isoantibodies are of which class?

IgM. ***IgM*** - Naturally occurring **ABO isoantibodies** are predominantly of the **IgM class**. - These **pentameric antibodies** are highly effective at causing **agglutination** of incompatible red blood cells, which is crucial in transfusion reactions [1]. *IgG* - While IgG antibodies can be formed against ABO antigens (e.g., in hemolytic disease of the newborn), the **naturally occurring isoantibodies** are primarily IgM. - IgG antibodies are **monomeric** and can cross the **placenta**, which is a key difference from the primary IgM ABO antibodies. *IgD* - **IgD** antibodies are primarily found on the surface of **B cells** and play a role in B cell activation. - They are **not a primary mediator** of ABO isoantibody response or red blood cell agglutination. *IgA* - **IgA** antibodies are predominantly found in **mucosal secretions** and play a role in mucosal immunity. - While some IgA may be present, it is **not the predominant class** for naturally occurring ABO isoantibodies involved in transfusion reactions. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 154-155.

Q: Which of the following statements about interleukin-1 is false?

IL-1 inhibits IL-2 production by T-cells.. ***IL-1 inhibits IL-2 production by T-cells*** - This statement is false because **IL-1** actually **enhances the production of IL-2** by T-cells, which is crucial for T-cell proliferation and immune response. - **IL-1 acts synergistically with IL-6 and TNF-α** to promote inflammation and immune cell activation, where IL-2 plays a key role. *The primary source of IL-1 is the monocyte-macrophage system* - This statement is true; **monocytes and macrophages** are the main producers of **IL-1α and IL-1β** upon activation by various stimuli. - Other cells, such as neutrophils, dendritic cells, and endothelial cells, can also produce IL-1, but monocytes and macrophages are the predominant source. *IL-1 is an endogenous pyrogen* - This statement is true; **IL-1** is a potent **endogenous pyrogen** that acts on the hypothalamus to induce fever, a hallmark of the acute phase response. - It triggers prostaglandin synthesis in the hypothalamus, leading to an elevation in the body's thermoregulatory set point. *IL-1 promotes acute phase protein synthesis in the liver* - This statement is true; **IL-1** is a key mediator that stimulates **hepatocytes** to produce **acute phase proteins**, such as C-reactive protein and serum amyloid A. - This hepatic response is part of the innate immune system's effort to control infection and inflammation.

Q: Which of the following antiretroviral drugs is not associated with peripheral neuropathy?

Indinavir. ***Indinavir*** - **Indinavir** is a **protease inhibitor** that can cause side effects such as **nephrolithiasis** (kidney stones) and **hyperbilirubinemia**, but it is generally *not associated with peripheral neuropathy*. - It works by blocking the viral protease enzyme, preventing the cleavage of viral polyproteins into functional proteins, which disrupts viral replication. *Stavudine* - **Stavudine** is a **nucleoside reverse transcriptase inhibitor (NRTI)** notorious for causing dose-dependent **peripheral neuropathy**. - This toxicity is due to its interference with **mitochondrial DNA synthesis**, leading to nerve damage. *Zalcitabine* - **Zalcitabine** (ddC) is another **NRTI** strongly associated with a high incidence of **peripheral neuropathy**. - Its mechanism of action and side effect profile are similar to those of stavudine in causing **mitochondrial toxicity**. *Didanosine* - **Didanosine** (ddI) is an **NRTI** known to cause several adverse effects, including **peripheral neuropathy**, particularly at higher doses. - Like other dideoxynucleoside analogs, its toxicity is linked to **mitochondrial dysfunction**.

Q: The best agent for increasing HDL cholesterol is?

Nicotinic acid. ***Nicotinic acid*** - **Nicotinic acid** (niacin) is known to significantly increase **high-density lipoprotein (HDL) cholesterol** levels by reducing its catabolism. - It also has beneficial effects on other lipid parameters, such as lowering **triglycerides** and **LDL cholesterol**. *Statin* - **Statins** (HMG-CoA reductase inhibitors) are highly effective at lowering **LDL cholesterol** and moderately lowering triglycerides. - While they can cause a modest increase in HDL cholesterol, their primary role is not HDL elevation. *Gugulipids* - **Gugulipids**, derived from the gum resin of the _Commiphora mukul_ tree, have been used in traditional medicine to lower cholesterol. - Evidence for their efficacy in significantly increasing HDL cholesterol is weak and not clinically recommended. *Fibrates* - **Fibrates** primarily work to lower **triglyceride levels** and can modestly increase HDL cholesterol. - Their effect on HDL is generally less pronounced compared to nicotinic acid.

Question 1

The BEINGS Model of disease causation does not include which of the following factors?

Accepted Answer

Spiritual factors

Answer

Religious factors

Answer

Social factors

Answer

Nutritional factors

Question 2

Which of the following is a superantigen ?

Accepted Answer

TSST

Answer

Cholera toxin

Answer

Diphtheria toxin

Answer

Vero-cytoxin

Question 3

Rosette formation with sheep RBCs (SRBCs) indicates functioning of -

Accepted Answer

T-cells

Answer

B-cells

Answer

Neutrophils

Answer

Monocytes

Question 4

Cytolytic activity of membrane attack complex is modulated by ?

Accepted Answer

Factor S (vitronectin)

Answer

Factor I

Answer

Factor B

Answer

Factor H

Question 5

What is the primary use of the Hybridoma technique?

Accepted Answer

Monoclonal antibodies

Answer

Antigen

Answer

Specific antibodies

Answer

Cytokines

Question 6

Which immunoglobulin is primarily secreted by the intestine?

Accepted Answer

IgA

Answer

IgG

Answer

IgM

Answer

IgD

Question 7

ABO isoantibodies are of which class?

Accepted Answer

IgM

Answer

IgG

Answer

IgD

Answer

IgA

Question 8

Which of the following statements about interleukin-1 is false?

Accepted Answer

IL-1 inhibits IL-2 production by T-cells.

Answer

IL-1 is an endogenous pyrogen.

Answer

The primary source of IL-1 is the monocyte-macrophage system.

Answer

IL-1 promotes acute phase protein synthesis in the liver.

Question 9

Which of the following antiretroviral drugs is not associated with peripheral neuropathy?

Accepted Answer

Indinavir

Answer

Stavudine

Answer

Zalcitabine

Answer

Didanosine

Question 10

The best agent for increasing HDL cholesterol is?

Accepted Answer

Nicotinic acid

Answer

Statin

Answer

Gugulipids

Answer

Fibrates

NEET-PG 2013

Community Medicine

Microbiology

Pathology

Pharmacology