Blood and Immunity Practice Questions

Q: Where does hematopoiesis occur in the first month of life?

Medullary. **Explanation:** The site of hematopoiesis changes dynamically during fetal development and early infancy. By the **first month of life**, the primary site of hematopoiesis is the **bone marrow (Medullary)**. **1. Why Medullary is correct:** The medullary phase begins around the 4th to 5th month of gestation. By the time a full-term infant is born, the bone marrow has taken over as the predominant site of blood cell production. During the first month of life, hematopoiesis is almost exclusively medullary to meet the infant's physiological demands. **2. Why the other options are incorrect:** * **Hepatic (Option B):** The liver is the chief site of hematopoiesis during the **second trimester** (peaking at 3–6 months gestation). While some residual activity may exist at birth, it ceases shortly thereafter under normal conditions. * **Lymphatic (Option C):** Lymph nodes and the spleen contribute to lymphopoiesis, but they are not the primary sites for general hematopoiesis (RBCs, granulocytes, platelets) in the neonatal period. * **Mesoblastic (Option D):** This is the **earliest stage**, occurring in the yolk sac. It begins around the 3rd week of gestation and ends by the 10th–12th week. **High-Yield Clinical Pearls for NEET-PG:** * **Sequence of Hematopoiesis:** Yolk Sac (Mesoblastic) → Liver/Spleen (Hepatic) → Bone Marrow (Medullary). * **Extramedullary Hematopoiesis:** If the bone marrow fails or is overwhelmed (e.g., in Thalassemia major or Myelofibrosis), the liver and spleen can resume hematopoiesis, leading to hepatosplenomegaly. * **Infant Bone Marrow:** In infants, almost all bones contain **red marrow** (active). As the child ages, red marrow is replaced by inactive **yellow marrow** (fatty), starting from the distal bones.

Q: What is the site of RBC formation in a 20-year-old healthy male?

Flat bones. **Explanation:** The site of erythropoiesis (RBC formation) changes dynamically throughout human development. In a **20-year-old healthy male**, the process is restricted to the **red bone marrow** of specific bones. **1. Why "Flat bones" is correct:** By the age of 20, the shaft of long bones (diaphysis) undergoes "fatty metamorphosis," where red marrow is replaced by inactive yellow marrow. Consequently, RBC production becomes confined to the **flat bones** (such as the sternum, ribs, skull, and iliac crest) and the **proximal ends** of the humerus and femur. **2. Analysis of Incorrect Options:** * **Short bones:** While they contain marrow, they are not the primary sites of active erythropoiesis in adults compared to the axial skeleton (flat bones). * **Liver:** This is the primary site of erythropoiesis during the **hepatic stage** (2nd to 7th month of intrauterine life). In adults, the liver only produces RBCs in pathological states (extramedullary hematopoiesis). * **Yolk sac:** This is the **first site** of erythropoiesis (Mesoblastic stage), starting around the 3rd week of gestation and ending by the 3rd month. **High-Yield Clinical Pearls for NEET-PG:** * **Chronology of Erythropoiesis:** Yolk Sac (3wk–3mo) → Liver/Spleen (1mo–9mo) → Bone Marrow (5th month onwards). * **Adult Marrow:** After age 20, the **Iliac crest** and **Sternum** are the most active sites; the iliac crest is the preferred site for bone marrow aspiration/biopsy. * **Extramedullary Hematopoiesis:** If the bone marrow fails (e.g., Myelofibrosis), the liver and spleen may resume RBC production, often leading to hepatosplenomegaly.

Q: The Rh factor is a:

Antibody. **Explanation:** The Rh factor (Rhesus factor) refers to a specific group of antigens found on the surface of red blood cells. However, in the context of this specific question (often seen in older physiological classifications), the term "Rh factor" is historically used to describe the **anti-Rh antibodies** (specifically Anti-D) that react with the Rh antigen. 1. **Why 'Antibody' is the correct answer:** In classical immunology nomenclature, a "factor" often refers to the reactive component in the serum. The Rh factor was discovered by Landsteiner and Wiener when they injected Rhesus monkey blood into rabbits; the rabbits produced an **antibody** (the Rh factor) that agglutinated human RBCs. In modern clinical practice, we distinguish between the Rh *antigen* (on the RBC) and the Rh *antibody* (in the serum), but for competitive exams, it is traditionally classified as an antibody. 2. **Why the other options are incorrect:** * **Mucopolysaccharide:** This describes the chemical nature of ABO blood group antigens (which are glycolipids and glycoproteins with carbohydrate side chains). * **Lipoprotein:** Rh antigens are non-glycosylated, hydrophobic proteins, but they are not classified as lipoproteins. * **Glycoprotein:** While many RBC surface markers are glycoproteins (like ABO), the Rh antigens (D, C, c, E, e) are unique because they are **pure transmembrane proteins** with no carbohydrate side chains. **High-Yield Clinical Pearls for NEET-PG:** * **Nature of Rh Antigen:** It is a non-glycosylated protein. * **Inheritance:** Rh antigens are encoded by two genes, *RHD* and *RHCE*, located on **Chromosome 1**. * **Clinical Significance:** Rh antibodies are **IgG** type. Unlike ABO antibodies, they cross the placenta, leading to **Erythroblastosis Fetalis** (Hemolytic Disease of the Newborn). * **Immunogenicity:** The **D antigen** is the most immunogenic of all non-ABO antigens.

Q: Which clotting factor is not affected in liver disease?

Factor VIII. **Explanation:** The liver is the primary site for the synthesis of almost all coagulation factors. However, **Factor VIII (Anti-hemophilic factor)** is the notable exception. While it is produced by various tissues, its primary source is the **vascular endothelial cells** (specifically in the liver sinusoids and other extrahepatic sites), rather than the hepatocytes. Therefore, in chronic liver disease, Factor VIII levels do not decrease; in fact, they often **increase** due to a compensatory mechanism or decreased clearance by the diseased liver. **Analysis of Options:** * **Factor II (Prothrombin):** Synthesized in hepatocytes and is Vitamin K-dependent. Its levels drop significantly in liver failure. * **Factor IV (Calcium):** This is an inorganic ion obtained from the diet and bone metabolism, not synthesized by the liver. However, in the context of "clotting factors synthesized by the liver," Factor VIII is the classic physiological exception taught for exams. * **Factor IX (Christmas Factor):** A Vitamin K-dependent factor synthesized exclusively by hepatocytes. Its deficiency is seen early in liver dysfunction. **High-Yield Clinical Pearls for NEET-PG:** 1. **Vitamin K Dependent Factors:** II, VII, IX, and X (all synthesized in the liver). 2. **Shortest Half-life:** Factor VII has the shortest half-life (4–6 hours), making **Prothrombin Time (PT)** the best early indicator of acute liver cell failure. 3. **Factor VIII and vWF:** Both are produced by endothelial cells (Weibel-Palade bodies) and remain elevated or normal in liver cirrhosis. 4. **Factor V:** Unlike Factor VIII, Factor V is synthesized in the liver. Comparing Factor V and Factor VIII levels can help differentiate between Vitamin K deficiency (Factor V normal) and true liver disease (Factor V low).

Q: Ferritin stores are present in the following sites except?

Intestine. ### Explanation The correct answer is **A. Intestine**. **1. Why Intestine is the correct answer:** Iron is stored in the body primarily in the form of **Ferritin** (soluble) and **Hemosiderin** (insoluble). While the mucosal cells of the small intestine (enterocytes) contain ferritin, it is considered a **"labile" or temporary pool** rather than a storage site. Iron in the intestine is either absorbed into the blood or lost when the mucosal cells are desquamated (sloughed off) every few days. Therefore, the intestine is not a site for long-term iron storage. **2. Analysis of Incorrect Options:** The Reticuloendothelial System (RES) and hepatocytes are the primary long-term reservoirs for iron: * **B. Liver:** The liver is the **primary storage site** for iron. Hepatocytes and Kupffer cells store the majority of the body's ferritin. * **C. Spleen:** Splenic macrophages recycle iron from aged red blood cells and store it as ferritin. * **D. Bone:** Bone marrow macrophages store iron to make it readily available for erythropoiesis (hemoglobin synthesis). **3. NEET-PG High-Yield Pearls:** * **Most sensitive index** for iron deficiency anemia (IDA): **Serum Ferritin** (it decreases before changes in hemoglobin or RBC morphology occur). * **Apoferritin + Iron = Ferritin.** * **Hepcidin:** The "Master Regulator" of iron metabolism; it inhibits iron release by binding to **Ferroportin**. * **Daily Iron Loss:** Approximately 1 mg/day (via desquamation of skin and intestinal cells). * **Site of maximum iron absorption:** Duodenum and upper jejunum.

Q: Splenectomy is expected to cause what change in the number of platelets?

Increase in the number of platelets. **Explanation:** **1. Why Option A is Correct:** The spleen normally acts as a major reservoir for platelets, sequestering approximately **one-third (30-33%)** of the total body platelet mass at any given time [1]. These platelets are in a state of dynamic equilibrium with the systemic circulation. When the spleen is removed (splenectomy), this sequestration site is lost [2]. Consequently, the platelets that would have been stored in the spleen are released into the peripheral blood, leading to **thrombocytosis** (an increase in platelet count). This rise is often immediate and can be significant, sometimes exceeding 1,000,000/µL in the postoperative period. **2. Why Other Options are Incorrect:** * **Option B & D:** Platelet production occurs in the bone marrow via megakaryocytes, not the spleen. Therefore, removing the spleen does not stop production or cause a decrease; rather, it removes the primary site of platelet destruction and storage. * **Option C:** Because the spleen holds a significant portion of the circulating mass, its removal invariably alters the peripheral blood count. **3. NEET-PG High-Yield Pearls:** * **Post-Splenectomy Blood Picture:** Look for **Howell-Jolly bodies** (nuclear remnants), **Pappenheimer bodies** (iron granules), **Heinz bodies** (denatured hemoglobin), and **Target cells** on the peripheral smear. * **Clinical Risk:** Extreme thrombocytosis post-splenectomy may rarely require hydroxyurea or aspirin if thrombotic events are a concern, though it is usually transient. * **Infections:** Patients are at lifelong risk of **OPSI (Overwhelming Post-Splenectomy Infection)** caused by encapsulated organisms (*S. pneumoniae, H. influenzae, N. meningitidis*). Vaccination is mandatory. * **Splenomegaly:** In cases of massive splenomegaly (e.g., Myelofibrosis), sequestration can increase to 90% [1], leading to peripheral thrombocytopenia.

Q: Respiratory burst is related to:

Sharp increase in O2 uptake and metabolism in neutrophils. **Explanation:** **Respiratory Burst** (also known as oxidative burst) is a rapid increase in oxygen consumption and metabolic activity within phagocytes, primarily **neutrophils and macrophages**, during the process of phagocytosis. 1. **Why Option C is Correct:** When a neutrophil encounters a pathogen, it activates the enzyme **NADPH oxidase**. This enzyme transfers electrons from NADPH to molecular oxygen ($O_2$), producing the **superoxide anion** ($O_2^-$). This sudden surge in oxygen uptake is not for cellular respiration (ATP production) but for generating **Reactive Oxygen Species (ROS)** like superoxide, hydrogen peroxide, and hypochlorous acid (via myeloperoxidase). these ROS are lethal to ingested bacteria and fungi. 2. **Why Other Options are Incorrect:** * **Option A & B:** These describe physiological breathing patterns related to the chemical control of respiration (chemoreceptors). Hyperventilation after apnea is a compensatory mechanism to wash out $CO_2$, while apnea after hyperventilation occurs because low $PaCO_2$ levels temporarily remove the stimulus to breathe. Neither is termed "respiratory burst." **High-Yield Clinical Pearls for NEET-PG:** * **Chronic Granulomatous Disease (CGD):** A high-yield genetic defect caused by a deficiency in **NADPH oxidase**. Patients cannot mount a respiratory burst, leading to recurrent infections with **catalase-positive organisms** (e.g., *S. aureus*, *Aspergillus*). * **Diagnostic Test:** The **Nitroblue Tetrazolium (NBT) test** or Dihydrorhodamine (DHR) flow cytometry is used to diagnose CGD by assessing the respiratory burst capability. * **Key Enzyme:** NADPH oxidase is located in the phagosome membrane.

Q: Dicumarol therapy would decrease the plasma concentration of which of the following procoagulants?

Prothrombin. Explanation: Dicumarol is a natural anticoagulant that functions as a Vitamin K antagonist, similar to Warfarin. It inhibits the enzyme Vitamin K Epoxide Reductase (VKOR), which is essential for recycling Vitamin K. [2] 1. Why Prothrombin is Correct: Vitamin K is a necessary cofactor for the gamma-carboxylation of glutamic acid residues on specific clotting factors. [1] This post-translational modification allows these factors to bind calcium and phospholipids, making them functional. The Vitamin K-dependent factors are II (Prothrombin), VII, IX, and X, as well as Proteins C and S. [2] By inhibiting Vitamin K recycling, Dicumarol leads to the production of dysfunctional factors and a decrease in the plasma concentration of active Prothrombin (Factor II). [3] 2. Why Incorrect Options are Wrong: * Fibrinogen (Factor I): Synthesized in the liver but does not require Vitamin K for its synthesis or activation. [3] * Factor VIII: A cofactor in the intrinsic pathway. It is not Vitamin K-dependent and is primarily produced by sinusoidal endothelial cells (not just hepatocytes). [3] * Factor V: A cofactor in the common pathway. While synthesized in the liver, its production is independent of Vitamin K. [3] High-Yield Clinical Pearls for NEET-PG: * Mnemonic for Vitamin K factors: "1972" (Factors 10, 9, 7, 2). [2] * Monitoring: Warfarin/Dicumarol therapy is monitored using PT (Prothrombin Time) and INR, as Factor VII has the shortest half-life and is affected first. * Antidote: For immediate reversal of Dicumarol/Warfarin overdose, use Fresh Frozen Plasma (FFP) or Prothrombin Complex Concentrate (PCC). For non-emergent reversal, use Vitamin K1 (Phytonadione). [1]

Question 1

Where does hematopoiesis occur in the first month of life?

Accepted Answer

Medullary

Answer

Hepatic

Answer

Lymphatic

Answer

Mesoblastic

Question 2

How do haemopoietic stem cells differ from committed progenitor cells in bone marrow?

Accepted Answer

Ability to provide long-term reconstitution of bone marrow

Answer

Presence of elaborate growth factors

Answer

Ability to alter receptor to protein binding

Answer

Capacity to provide permanent structure

Question 3

The Bombay blood group contains which of the following antibodies?

Accepted Answer

Anti A, Anti B, and Anti H

Answer

Anti H

Answer

Anti A and Anti B

Answer

H antibody along with H antigen

Question 4

What is the site of RBC formation in a 20-year-old healthy male?

Accepted Answer

Flat bones

Answer

Short bones

Answer

Liver

Answer

Yolk sac

Question 5

The Rh factor is a:

Accepted Answer

Antibody

Answer

Mucopolysaccharide

Answer

Lipoprotein

Answer

Glycoprotein

Question 6

Which clotting factor is not affected in liver disease?

Accepted Answer

Factor VIII

Answer

Factor II

Answer

Factor IV

Answer

Factor IX

Question 7

Ferritin stores are present in the following sites except?

Accepted Answer

Intestine

Answer

Liver

Answer

Spleen

Answer

Bone

Question 8

Splenectomy is expected to cause what change in the number of platelets?

Accepted Answer

Increase in the number of platelets

Answer

Decrease in the number of platelets

Answer

No change in the number of platelets

Answer

Complete absence of platelets

Question 9

Respiratory burst is related to:

Accepted Answer

Sharp increase in O2 uptake and metabolism in neutrophils

Answer

Hyperventilation after a period of apnea

Answer

Apnea after a period of hyperventilation

Answer

None of the above

Question 10

Dicumarol therapy would decrease the plasma concentration of which of the following procoagulants?

Accepted Answer

Prothrombin

Answer

Fibrinogen

Answer

Factor VIII

Answer

Factor V

Blood and Immunity — MCQs

Blood and Immunity — MCQs

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