Blood and Immunity Practice Questions

Q: Von Willebrand's factor is synthesized in which one of the following?

Vascular endothelium. **Explanation:** **Von Willebrand Factor (vWF)** is a large multimeric glycoprotein essential for primary hemostasis. It acts as a molecular bridge between the subendothelial collagen and platelets (via the GpIb receptor) and serves as a carrier protein for Factor VIII. **Why Vascular Endothelium is Correct:** vWF is primarily synthesized in two locations: 1. **Vascular Endothelial Cells:** Here, it is stored in specialized secretory organelles called **Weibel-Palade bodies**. 2. **Megakaryocytes:** It is synthesized here and subsequently stored in the **$\alpha$-granules of platelets**. Upon vascular injury, vWF is released from these sites to initiate platelet adhesion. **Why Other Options are Incorrect:** * **Macrophages:** These are phagocytic cells of the immune system and do not synthesize clotting factors. * **Liver:** While the liver is the primary site for the synthesis of most coagulation factors (like Fibrinogen, Prothrombin, and Factors VII, IX, X), it is **not** the source of vWF. This is a common "trap" in exams. * **Eosinophils:** These are granulocytes involved in allergic reactions and parasitic infections; they have no role in vWF production. **High-Yield Clinical Pearls for NEET-PG:** * **vWF and Factor VIII:** vWF stabilizes Factor VIII in circulation, increasing its half-life. In von Willebrand Disease (vWD), Factor VIII levels may also be low. * **Ristocetin Cofactor Assay:** This is the gold standard test for vWF function; Ristocetin induces platelet agglutination only in the presence of vWF. * **Desmopressin (DDAVP):** Used in treatment as it stimulates the release of vWF from Weibel-Palade bodies. * **vWD:** It is the most common inherited bleeding disorder.

Q: Iron absorption is increased in which of the following conditions?

Iron deficiency anemia. **Explanation:** Iron absorption is a tightly regulated process primarily controlled by the hormone **Hepcidin**, which is synthesized in the liver. Hepcidin acts by binding to and degrading **Ferroportin**, the only known cellular iron exporter [2]. **1. Why Iron Deficiency Anemia (IDA) is correct:** In IDA, the body’s iron stores are depleted. Low iron levels and increased erythropoietic activity signal the liver to **decrease Hepcidin production** [4]. Low hepcidin levels allow Ferroportin to remain active on the basolateral membrane of enterocytes, significantly increasing the absorption of dietary iron into the bloodstream [3]. **2. Analysis of Incorrect Options:** * **Pregnancy:** While iron *demand* increases significantly during pregnancy, the physiological state itself does not automatically increase absorption efficiency as much as a diagnosed deficiency state does [1]. However, if a pregnant woman develops IDA, absorption increases via the hepcidin mechanism. * **All types of anemia:** This is incorrect because **Anemia of Chronic Disease (ACD)** is characterized by *decreased* iron absorption. In ACD, inflammatory cytokines (like IL-6) increase hepcidin, which traps iron inside macrophages and enterocytes [3]. * **Malignancy:** Similar to chronic inflammation, malignancy often leads to an increase in hepcidin, causing "iron locking" and reduced intestinal absorption [1]. **NEET-PG High-Yield Pearls:** * **Site of absorption:** Primarily the **Duodenum** and upper Jejunum. * **Form of absorption:** Iron must be in the **Ferrous (Fe²⁺)** state to be absorbed via the DMT-1 transporter. Vitamin C (Ascorbic acid) aids this by reducing Ferric (Fe³⁺) to Ferrous. * **Hepcidin Regulation:** It is an **acute-phase reactant**. It increases in inflammation (decreasing absorption) and decreases in hypoxia or ineffective erythropoiesis (increasing absorption) [4].

Q: All of the following are true about Von Willebrand factor except:

Synthesized by hepatocytes. Explanation: 1. Why Option A is correct (The Exception): Von Willebrand Factor (vWF) is not synthesized by hepatocytes. Instead, it is synthesized and secreted by two specific cell types: Vascular Endothelial Cells (where it is stored in Weibel-Palade bodies) and Megakaryocytes (where it is stored in the $\alpha$-granules of platelets). Most other coagulation factors are produced in the liver, making this a high-yield distinction in histology and hematology [1]. 2. Why the other options are incorrect (True statements): * Option B & D: vWF serves as a vital carrier protein for Factor VIII in the plasma [2]. It protects Factor VIII from rapid proteolytic degradation by Protein C. Therefore, a deficiency in vWF leads to a secondary decrease in Factor VIII levels, mimicking or complicating hemophilia-like symptoms [1]. * Option C: vWF acts as a "molecular bridge" during primary hemostasis. It binds to subendothelial collagen and the GpIb receptor on platelets, facilitating platelet adhesion to the site of vascular injury. Deficiency leads to impaired platelet plug formation. Clinical Pearls for NEET-PG: * Weibel-Palade bodies: These are the hallmark electron microscopic features of endothelial cells containing vWF and P-selectin. * vWF Disease: The most common inherited bleeding disorder. * Ristocetin Cofactor Assay: Used to test vWF function; ristocetin induces vWF-induced platelet agglutination. * Desmopressin (DDAVP): Used in treatment as it stimulates the release of vWF from endothelial stores.

Q: Erythropoietin can be produced by which organ?

Kidney. **Explanation:** **Erythropoietin (EPO)** is a glycoprotein hormone that serves as the primary regulator of erythropoiesis (red blood cell production). 1. **Why Kidney is Correct:** In adults, approximately **85-90% of EPO** is synthesized by the **peritubular interstitial cells** (fibroblast-like cells) in the renal cortex. These cells act as oxygen sensors; when they detect hypoxia (low oxygen tension), they trigger the production of Hypoxia-Inducible Factor (HIF-1α), which stimulates the EPO gene to increase hormone production. The remaining 10-15% is produced by the liver (perisinusoidal cells). 2. **Why Other Options are Incorrect:** * **Brain:** While small amounts of EPO mRNA have been detected in the brain (astrocytes) for neuroprotective roles, it is not a primary site for systemic erythropoietin production. * **Bone Marrow:** This is the **target organ** where EPO acts, not where it is produced. EPO binds to receptors on erythroid progenitor cells (CFU-E) in the bone marrow to prevent apoptosis and stimulate maturation. * **Adipose Tissue:** This tissue primarily secretes adipokines (like leptin) and is not involved in the erythropoietic pathway. **High-Yield Clinical Pearls for NEET-PG:** * **Site of Action:** EPO acts specifically on the **CFU-E (Colony Forming Unit-Erythroid)** stage. * **Fetal Life:** In the fetus, the **liver** is the primary source of EPO; the switch to the kidney occurs near birth. * **Clinical Correlation:** Chronic Kidney Disease (CKD) leads to a deficiency of EPO, resulting in **normocytic normochromic anemia**. This is treated with recombinant human erythropoietin (Epoetin alfa). * **Polycythemia:** Renal Cell Carcinoma (RCC) can sometimes produce ectopic EPO, leading to secondary polycythemia.

Q: Which of the following enzymes does the neutrophil use to initiate the production of toxic oxygen compounds that kill bacteria?

NADPH oxidase. ### Explanation The process by which neutrophils destroy bacteria using oxygen-dependent mechanisms is known as the **Respiratory Burst** (or Oxidative Burst). **Why NADPH Oxidase is Correct:** The "trigger" or initiating enzyme for this process is **NADPH oxidase**, located in the membrane of the phagolysosome. It catalyzes the transfer of an electron from NADPH to molecular oxygen ($O_2$), converting it into the **Superoxide anion ($O_2^-$)**. This is the critical first step in the production of Reactive Oxygen Species (ROS). **Analysis of Incorrect Options:** * **Superoxide (D):** This is the *product* of the reaction catalyzed by NADPH oxidase, not the enzyme itself. * **Hydrogen Peroxide (A):** This is a secondary metabolite formed when Superoxide undergoes spontaneous or enzymatic dismutation (via Superoxide Dismutase). It is a precursor to more potent toxins but does not initiate the burst. * **Myeloperoxidase (B):** This enzyme acts later in the pathway. It uses Hydrogen Peroxide and chloride ions to produce **Hypochlorous acid (HOCl)**, which is the active ingredient in household bleach and the most potent bactericidal agent in neutrophils. **High-Yield Clinical Pearls for NEET-PG:** * **Chronic Granulomatous Disease (CGD):** Caused by a genetic deficiency in **NADPH oxidase**. Patients suffer from recurrent infections with **catalase-positive organisms** (e.g., *S. aureus*, *Aspergillus*) because they cannot produce their own ROS. * **Nitroblue Tetrazolium (NBT) Test:** Historically used to diagnose CGD; a positive test (blue color) indicates functional NADPH oxidase. * **MPO Deficiency:** Usually asymptomatic because the preceding ROS (Superoxide and $H_2O_2$) are still produced, though the killing process is slower.

Q: All of the following are categorized as secondary lymphoid organs except:

Thymus. ### Explanation The lymphoid system is divided into two functional categories: **Primary (Central)** and **Secondary (Peripheral)** lymphoid organs. **1. Why Thymus is the Correct Answer:** The **Thymus** and **Bone Marrow** are the **Primary Lymphoid Organs**. These are the sites where lymphocytes are generated (lymphopoiesis) and undergo antigen-independent maturation. In the thymus, T-cell precursors from the bone marrow differentiate into mature, immunocompetent T-lymphocytes. Since the question asks for the exception among secondary organs, the Thymus is the correct choice. **2. Analysis of Incorrect Options (Secondary Lymphoid Organs):** Secondary lymphoid organs are sites where mature lymphocytes reside, encounter antigens, and initiate an immune response (antigen-dependent activation). * **Lymph Nodes (Option A):** Filter lymph and are the primary site for neutralizing antigens from local tissues. * **Spleen (Option B):** Filters blood and mounts immune responses against blood-borne pathogens. * **Subepithelial collections (Option D):** These include **MALT** (Mucosa-Associated Lymphoid Tissue), such as Peyer’s patches in the small intestine, tonsils, and appendix. They protect mucosal surfaces. **Clinical Pearls & High-Yield Facts for NEET-PG:** * **Hassall’s Corpuscles:** Characteristic histological feature of the Thymic medulla. * **Thymic Involution:** The thymus is most active in childhood and undergoes fatty replacement (involution) after puberty. * **DiGeorge Syndrome:** Congenital failure of the 3rd and 4th pharyngeal pouches to develop, leading to thymic aplasia and T-cell deficiency. * **B-cell Maturation:** Occurs in the Bone Marrow (Primary), while their activation and proliferation into plasma cells occur in the Germinal Centers of secondary lymphoid organs.

Q: Which of the following factors is NOT involved in the intrinsic pathway of coagulation?

Factor VII. The coagulation cascade is divided into the Intrinsic, Extrinsic, and Common pathways. Understanding which factors belong to each is a high-yield requirement for NEET-PG. ### **Explanation** **Factor VII** is the correct answer because it is the primary component of the **Extrinsic Pathway**. The extrinsic pathway is triggered by "Tissue Factor" (Factor III) following vascular injury, which then activates Factor VII to form the TF-VIIa complex. **Why the other options are incorrect:** The **Intrinsic Pathway** (Contact Activation Pathway) involves factors that are present within the circulating blood. It is triggered when blood comes into contact with collagen or a negatively charged surface. * **Factor XII (Hageman factor):** The starting point of the intrinsic pathway. * **Factor XI:** Activated by Factor XIIa. * **Factor IX (Christmas factor):** Activated by Factor XIa. * **Factor VIII (Anti-hemophilic factor):** Acts as a cofactor for Factor IXa to activate the common pathway. ### **High-Yield Clinical Pearls** * **Memory Aid:** To remember the Intrinsic Pathway factors, think **"TENET"** (Twelve, Eleven, Nine, Eight, Ten). Note that Factor X is where the pathways merge into the **Common Pathway** (Factors X, V, II, I). * **Laboratory Correlation:** * **PT (Prothrombin Time)** measures the **Extrinsic** and Common pathways (specifically Factor VII). * **aPTT (activated Partial Thromboplastin Time)** measures the **Intrinsic** and Common pathways. * **Vitamin K Dependent Factors:** Factors II, VII, IX, and X (Remember: **1972**). Factor VII has the shortest half-life among these.

Q: Oedema occurs when plasma protein level is below which value?

5 mg/dl. **Explanation:** The development of oedema is primarily governed by **Starling’s Forces**, which regulate fluid exchange between capillaries and the interstitium. The two main opposing forces are Capillary Hydrostatic Pressure (pushing fluid out) and **Plasma Colloid Osmotic Pressure (COP)** (pulling fluid in). **Why 5 mg/dl is correct:** Plasma proteins, specifically **Albumin** (which contributes 70-80% of the COP), are responsible for maintaining an oncotic pressure of approximately 25-28 mmHg. When total plasma protein levels fall below **5 g/dl** (specifically when albumin falls below **2.5 g/dl**), the COP decreases significantly. This allows hydrostatic pressure to dominate, leading to the excessive filtration of fluid into the interstitial space, resulting in clinical oedema. **Analysis of Incorrect Options:** * **A & D (8 mg/dl & 10 mg/dl):** These values are within or above the normal range for total plasma proteins (Normal: 6–8 g/dl). At these levels, oncotic pressure is sufficient to prevent fluid leakage. * **B (2 mg/dl):** While oedema certainly occurs at 2 g/dl, this is a state of severe hypoproteinemia (often seen in advanced Nephrotic syndrome or Kwashiorkor). The threshold or "critical level" at which oedema *begins* to manifest is 5 g/dl. **High-Yield Clinical Pearls for NEET-PG:** * **Hypoproteinemic Oedema:** Characteristically presents as **pitting oedema** and is often first seen in lax tissue like the eyelids (periorbital oedema) or dependent parts (feet). * **Albumin vs. Globulin:** Albumin is more important for COP than globulin because it has a lower molecular weight (more molecules per unit weight) and a higher concentration. * **Mnemonic:** Remember the **"Rule of 5 & 2.5"**—Oedema occurs when Total Protein < 5 g/dl or Albumin < 2.5 g/dl.

Question 1

Von Willebrand's factor is synthesized in which one of the following?

Accepted Answer

Vascular endothelium

Answer

Macrophages

Answer

Liver

Answer

Eosinophils

Question 2

Iron absorption is increased in which of the following conditions?

Accepted Answer

Iron deficiency anemia

Answer

Pregnancy

Answer

All types of anemia

Answer

Malignancy

Question 3

All of the following are true about Von Willebrand factor except:

Accepted Answer

Synthesized by hepatocytes

Answer

Its deficiency can cause a Factor VIII defect

Answer

Its deficiency can cause problems with platelet adhesion

Answer

It serves as a carrier for Factor VIII

Question 4

Which of the following WBCs is important for mucosal immunity?

Accepted Answer

Lymphocytes

Answer

Neutrophils

Answer

Basophils

Answer

Eosinophils

Question 5

Failure of clot retraction indicates which of the following?

Accepted Answer

Low platelet count

Answer

Factor VIII deficiency

Answer

Factor XIII deficiency

Answer

Fibrinogen deficiency

Question 6

Erythropoietin can be produced by which organ?

Accepted Answer

Kidney

Answer

Brain

Answer

Bone marrow

Answer

Adipose tissue

Question 7

Which of the following enzymes does the neutrophil use to initiate the production of toxic oxygen compounds that kill bacteria?

Accepted Answer

NADPH oxidase

Answer

Hydrogen peroxide

Answer

Myeloperoxidase

Answer

Superoxide

Question 8

All of the following are categorized as secondary lymphoid organs except:

Accepted Answer

Thymus

Answer

Lymph nodes

Answer

Spleen

Answer

Subepithelial collections of lymphocytes

Question 9

Which of the following factors is NOT involved in the intrinsic pathway of coagulation?

Accepted Answer

Factor VII

Answer

Factor VIII

Answer

Factor IX

Answer

Factor XII

Question 10

Oedema occurs when plasma protein level is below which value?

Accepted Answer

5 mg/dl

Answer

8 mg/dl

Answer

2 mg/dl

Answer

10 mg/dl

Blood and Immunity — MCQs

Blood and Immunity — MCQs

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