Blood and Immunity Practice Questions

Q: Which anticoagulant is produced by mast cells?

Heparin. **Explanation:** **Heparin** is the correct answer because it is a naturally occurring anticoagulant synthesized and stored in the secretory granules of **mast cells** and **basophils**. Chemically, it is a highly sulfated glycosaminoglycan. Its primary physiological role is to prevent the formation of fibrin clots by binding to and significantly accelerating the activity of Antithrombin III, which inactivates Thrombin (Factor IIa) and Factor Xa. **Analysis of Incorrect Options:** * **Antithrombin III (A):** This is a plasma glycoprotein synthesized primarily in the **liver**. It is a natural inhibitor of coagulation, but it is not produced by mast cells. * **Protein C (B) and Protein S (C):** Both are Vitamin K-dependent glycoproteins synthesized in the **liver**. Protein C, when activated by the thrombin-thrombomodulin complex, degrades Factors Va and VIIIa. Protein S acts as a cofactor for Protein C. **Clinical Pearls for NEET-PG:** * **Mast Cell Locations:** Mast cells are abundant in tissues exposed to the external environment, particularly the **lungs, liver, and skin**, which explains why these tissues are rich sources of endogenous heparin. * **Antidote:** The anticoagulant effect of heparin can be rapidly neutralized by **Protamine Sulfate** (a positively charged molecule that binds to negatively charged heparin). * **Monitoring:** Unfractionated Heparin (UFH) therapy is monitored using **aPTT** (activated Partial Thromboplastin Time). * **Histology:** Mast cell granules show **metachromasia** (change color) when stained with Toluidine blue due to the high content of heparin.

Q: Which type of white blood cell has the longest lifespan?

Lymphocytes. The lifespan of white blood cells (WBCs) varies significantly based on their function and circulation patterns. **Lymphocytes** are the correct answer because they are the only leukocytes capable of recirculating between the blood and lymphoid tissues. While some effector lymphocytes live only a few days, **memory B and T cells** can persist for several years, and in some cases, decades, providing long-term immunity [2]. **Analysis of Incorrect Options:** * **Neutrophils:** These are the most abundant but shortest-lived WBCs. In the bloodstream, they circulate for only 6–10 hours [3], and once they migrate into tissues to perform phagocytosis, they survive for just 1–4 days. * **Eosinophils:** These cells typically circulate in the blood for about 8–12 hours before migrating into tissues (primarily the respiratory and GI tracts), where they survive for roughly 8–12 days. * **Monocytes:** These circulate for approximately 1–3 days [1]. However, once they enter tissues and differentiate into **macrophages**, they can live for several months [1]. Despite this, they do not match the multi-year longevity of memory lymphocytes. **High-Yield Clinical Pearls for NEET-PG:** * **Recirculation:** Lymphocytes are the only WBCs that return to the blood after entering tissues [2]. * **Order of Lifespan (Shortest to Longest):** Neutrophils < Eosinophils < Monocytes < Lymphocytes. * **Granulocytes vs. Agranulocytes:** Granulocytes (Neutrophils, Eosinophils, Basophils) generally have much shorter lifespans compared to agranulocytes (Monocytes, Lymphocytes).

Q: Which of the following is NOT secreted by eosinophils?

Hydrolytic enzyme. The correct answer is **B. Hydrolytic enzyme**. While eosinophils are granulocytes equipped with various cytotoxic mediators, they are notably deficient in **lysozymes** and certain specific hydrolytic enzymes typically found in neutrophils and macrophages [1]. Their primary function is the extracellular destruction of large parasites rather than the intracellular digestion of bacteria. **Analysis of Options:** * **Major Basic Protein (MBP):** This is the most abundant protein in the eosinophilic cation granules. It is highly toxic to helminths (parasites) and mammalian cells, causing membrane disruption. * **Reactive forms of Oxygen:** Like other phagocytes, eosinophils undergo a "respiratory burst" using the enzyme **Eosinophil Peroxidase (EPO)** to produce superoxide, hydrogen peroxide, and hypobromous acid to kill invading pathogens. * **Eosinophilic Chemotactic Factor (ECF):** Eosinophils release various cytokines and lipid mediators (like Leukotriene C4) that act as chemotactic signals to recruit more eosinophils and inflammatory cells to the site of infection or allergic reaction [1]. **High-Yield NEET-PG Pearls:** 1. **Granule Contents:** Eosinophil granules contain four major proteins: Major Basic Protein (MBP), Eosinophil Cationic Protein (ECP), Eosinophil-Derived Neurotoxin (EDN), and Eosinophil Peroxidase (EPO) [1]. 2. **Charcot-Leyden Crystals:** These are hexagonal, needle-like crystals found in sputum (asthma) or stool (parasitic infections), formed from the breakdown of **Galectin-10** (lysophospholipase) in eosinophils. 3. **Clinical Association:** Eosinophilia is classically seen in **NAACP**: **N**eoplasia, **A**llergy/Asthma, **A**ddison’s disease, **C**onnective tissue disorders, and **P**arasites [1].

Q: Which of the following methods is not used for hemoglobin estimation?

Wintrobe method. **Explanation:** The **Wintrobe method** is the correct answer because it is used for the estimation of **Packed Cell Volume (PCV) or Hematocrit**, and the **Erythrocyte Sedimentation Rate (ESR)**, not for hemoglobin estimation. It involves using a Wintrobe tube (110 mm long) to centrifuge blood and measure the volume of packed red cells. **Analysis of other options:** * **Drabkin’s Method (Cyanmethemoglobin method):** This is the **gold standard** and the most accurate method for hemoglobin estimation. It converts hemoglobin into cyanmethemoglobin, which is then measured using a colorimeter at 540 nm. * **Sahli’s Method (Acid Hematin method):** A common bedside/laboratory method where hemoglobin is converted into brown-colored acid hematin by adding 0.1 N HCl. The color is then matched against a standard glass comparator. * **Spectrophotometry:** This is the underlying principle for most automated analyzers and the Drabkin’s method. It measures the light absorbance of a hemoglobin derivative to calculate concentration. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard for Hb:** Drabkin’s method (measures all forms of Hb except sulfhemoglobin). * **Wintrobe Tube:** Length is 110 mm; internal diameter is 3 mm. It can measure both ESR (0–100 mm) and PCV (0–100%). * **Westergren Method:** The preferred and most sensitive method for measuring **ESR** (uses a 300 mm tube). * **Sahli’s Disadvantage:** It does not measure carboxyhemoglobin, methemoglobin, or sulfhemoglobin, making it less accurate than Drabkin’s.

Q: ABO antigens are not present in which of the following?

Cerebrospinal fluid (CSF). **Explanation:** The ABO blood group system is based on the presence of specific carbohydrate antigens (A and B) on the surface of red blood cells. However, these antigens are not restricted to erythrocytes; they are widely distributed throughout the body. **1. Why CSF is the correct answer:** ABO antigens are notably **absent in the Cerebrospinal Fluid (CSF)**. The blood-brain barrier (BBB) and the blood-CSF barrier are highly selective. Since ABO antigens are primarily found on cell membranes or as large glycoconjugates in secretions, they do not cross into the CSF. Furthermore, the central nervous system lacks the expression of these antigens on its parenchymal cells. **2. Analysis of incorrect options:** * **Blood (Option C):** This is the primary site. Antigens are found on RBCs, WBCs, and platelets. * **Saliva and Tears (Options A & D):** In approximately **80% of the population (known as "Secretors")**, ABO antigens are found in a water-soluble form in body fluids. This is governed by the **Se gene (FUT2)**. These secretors will have A, B, or H antigens in their saliva, tears, sweat, semen, and digestive juices. **Clinical Pearls & High-Yield Facts for NEET-PG:** * **Secretor Status:** Controlled by the *Se* gene on chromosome 19. If a person is a "secretor," their blood type can be determined using their saliva—a fact often used in forensic medicine. * **Distribution:** ABO antigens are also found on the surface of vascular endothelial cells and most epithelial cells (except in the CNS). * **Bombay Phenotype (hh):** These individuals lack the H antigen (the precursor for A and B). They will not have A or B antigens in their blood or secretions, even if they possess the A or B genes. * **Universal Rule:** If a question asks where ABO antigens are *absent*, the most common high-yield answers are **CSF and Hair** (except the hair root).

Q: Which of the following is NOT a function of the reticuloendothelial system?

Bilirubin metabolism. The **Reticuloendothelial System (RES)**, now more commonly known as the **Mononuclear Phagocyte System (MPS)**, consists of phagocytic cells (monocytes and macrophages) located in reticular connective tissue, primarily in the spleen, liver (Kupffer cells), and lymph nodes. ### **Why "Bilirubin Metabolism" is the Correct Answer** While the RES is responsible for the **formation** of bilirubin (by breaking down hemoglobin from old RBCs), it does **not** perform bilirubin **metabolism** (conjugation). Bilirubin metabolism—specifically the conjugation of unconjugated bilirubin with glucuronic acid—is a metabolic function exclusive to the **hepatocytes** (parenchymal cells of the liver), not the phagocytic cells of the RES. ### **Explanation of Incorrect Options** * **A. Antibody production:** Macrophages in the RES act as Antigen-Presenting Cells (APCs). They process pathogens and present antigens to B-lymphocytes, which then differentiate into plasma cells to produce antibodies. * **B. Destruction of RBCs:** This is a primary function. The "graveyard of RBCs" (the spleen) is a major component of the RES, where macrophages sequester and destroy senescent (old) erythrocytes. * **C. Phagocytosis:** This is the hallmark functional characteristic of the RES. These cells ingest and destroy bacteria, viruses, and foreign particulate matter to clear the circulation. ### **High-Yield Clinical Pearls for NEET-PG** * **Components of RES:** Includes Kupffer cells (liver), Microglia (CNS), Alveolar macrophages (lungs), Mesangial cells (kidney), and Osteoclasts (bone). * **Heme Breakdown:** RES converts Heme → Biliverdin → **Unconjugated Bilirubin**. * **Key Distinction:** RES = Bilirubin *Production*; Hepatocytes = Bilirubin *Conjugation/Excretion*. * **Storage:** The RES also plays a role in iron metabolism by storing iron as ferritin or hemosiderin following RBC destruction.

Q: Arrange the following in the sequential order of appearance during the intrinsic clotting pathway: Phospholipid, Prekallikrein, Activated Factor V, Factor XIII?

Prekallikrein-Phospholipid-Activated Factor V-Factor XIII. To master the coagulation cascade for NEET-PG, it is essential to distinguish between the **Intrinsic**, **Extrinsic**, and **Common** pathways. ### **Explanation of the Correct Sequence** The sequence follows the chronological activation of the clotting cascade: 1. **Prekallikrein:** This is part of the **Contact Activation Phase** (Intrinsic Pathway). When blood contacts a negatively charged surface, Factor XII is activated, a process facilitated by High Molecular Weight Kininogen (HMWK) and Prekallikrein. 2. **Phospholipid:** As the cascade progresses to the activation of Factor IX and X, **Platelet Factor 3 (Phospholipid)** acts as a surface cofactor for the "Tenase" and "Prothrombinase" complexes. 3. **Activated Factor V (Va):** This is a cofactor in the **Common Pathway**. It combines with Factor Xa, Calcium, and Phospholipids to form the Prothrombinase complex, which converts Prothrombin to Thrombin. 4. **Factor XIII:** This is the **final step**. Once Thrombin converts Fibrinogen to Fibrin monomers, Factor XIII (Fibrin Stabilizing Factor) cross-links these monomers to form a stable, insoluble clot. ### **Why Other Options are Incorrect** * **Options B, C, and D** are incorrect because they misplace the hierarchy of the cascade. Prekallikrein must act at the start (Intrinsic), while Factor XIII must always be at the end (Clot stabilization). Factor V cannot precede the contact phase. ### **High-Yield NEET-PG Pearls** * **Rate-Limiting Step:** The activation of Factor X is the point where Intrinsic and Extrinsic pathways converge into the Common Pathway. * **Vitamin K Dependent Factors:** II, VII, IX, X, Protein C, and Protein S. * **Lab Correlation:** The Intrinsic pathway is measured by **aPTT**, while the Extrinsic pathway is measured by **PT/INR**. * **Factor IV:** This is simply Calcium ions ($Ca^{2+}$), required at almost every step except the initial contact phase.

Q: Platelet adhesion to collagen occurs via which of the following?

Von-Willebrand factor. **Explanation:** Platelet plug formation occurs in three distinct stages: **Adhesion, Activation, and Aggregation.** **1. Why Von-Willebrand Factor (vWF) is correct:** When a blood vessel is injured, the subendothelial collagen is exposed. Platelets cannot bind directly to collagen under high-shear conditions (like in arteries). **Von-Willebrand Factor (vWF)** acts as a molecular bridge. One end of the vWF molecule binds to the exposed **collagen**, while the other end binds to the **Glycoprotein Ib-IX-V (GpIb)** receptor on the platelet surface. This tethering is the critical first step in primary hemostasis. **2. Why the other options are incorrect:** * **Factor VIII:** While vWF acts as a carrier protein for Factor VIII in the circulation to prevent its degradation, Factor VIII itself is a cofactor in the coagulation cascade (intrinsic pathway) and does not mediate platelet adhesion. * **Factor IX (Christmas Factor):** This is a serine protease in the intrinsic pathway of the coagulation cascade. Its deficiency leads to Hemophilia B. * **Fibronectin:** Although fibronectin is involved in cell adhesion and wound healing, it is not the primary mediator for the initial attachment of platelets to the subendothelium in high-flow vessels. **Clinical Pearls for NEET-PG:** * **Bernard-Soulier Syndrome:** Caused by a deficiency of the **GpIb** receptor; results in defective platelet **adhesion** and "Giant Platelets." * **Glanzmann Thrombasthenia:** Caused by a deficiency of **GpIIb/IIIa**; results in defective platelet **aggregation**. * **vWF Source:** It is synthesized and stored in **Weibel-Palade bodies** of endothelial cells and **alpha-granules** of platelets. * **Ristocetin Assay:** Used to test vWF function; ristocetin induces platelet agglutination by activating vWF to bind GpIb.

Question 1

Which anticoagulant is produced by mast cells?

Accepted Answer

Heparin

Answer

Antithrombin III

Answer

Protein C

Answer

Protein S

Question 2

Which type of white blood cell has the longest lifespan?

Accepted Answer

Lymphocytes

Answer

Eosinophil

Answer

Neutrophil

Answer

Monocytes

Question 3

In an ablated animal model, myeloid series cells are injected. Which of the following is observed after an incubation period?

Accepted Answer

RBCs

Answer

Fibroblasts

Answer

T lymphocytes

Answer

Hematopoietic stem cells

Question 4

Which of the following is NOT secreted by eosinophils?

Accepted Answer

Hydrolytic enzyme

Answer

Major basic protein

Answer

Reactive form of oxygen

Answer

Eosinophilic chemotactic factor

Question 5

What is the primary function of hemoglobin regarding oxygen transport?

Accepted Answer

To increase oxygen uptake in the lungs and delivery at tissues.

Answer

To increase oxygen delivery in the lungs and uptake at tissues.

Answer

To increase carbon dioxide delivery at tissues and uptake in the lungs.

Answer

None of the above.

Question 6

Which of the following methods is not used for hemoglobin estimation?

Accepted Answer

Wintrobe method

Answer

Drabkin's method

Answer

Sahli's method

Answer

Spectrophotometry

Question 7

ABO antigens are not present in which of the following?

Accepted Answer

Cerebrospinal fluid (CSF)

Answer

Saliva

Answer

Blood

Answer

Tear

Question 8

Which of the following is NOT a function of the reticuloendothelial system?

Accepted Answer

Bilirubin metabolism

Answer

Antibody production

Answer

Destruction of RBCs

Answer

Phagocytosis

Question 9

Arrange the following in the sequential order of appearance during the intrinsic clotting pathway: Phospholipid, Prekallikrein, Activated Factor V, Factor XIII?

Accepted Answer

Prekallikrein-Phospholipid-Activated Factor V-Factor XIII

Answer

Phospholipid-Activated Factor V-Factor XIII-Prekallikrein

Answer

Factor XIII-Prekallikrein-Phospholipid-Activated Factor V

Answer

Prekallikrein-Factor XIII-Activated Factor V-Phospholipid

Question 10

Platelet adhesion to collagen occurs via which of the following?

Accepted Answer

Von-Willebrand factor

Answer

Factor VIII

Answer

Factor IX

Answer

Fibronectin

Blood and Immunity — MCQs

Blood and Immunity — MCQs

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