Blood and Immunity — MCQs

A 40-year-old female patient complains of excessive bleeding following a road traffic accident 5 hours ago, with a lacerated wound on the lower back. Blood grouping tests reveal the presence of antigen A and antigen H. Anti-RhD antibodies and anti-B antibodies are also present. Which donor blood group can this patient receive transfusion from?

Q368Easy

Anti-A and anti-B antibodies appear in a child when?

Q369Easy

Hagemann factor is involved in which pathway of coagulation?

Q370Medium

Bleeding time is not prolonged in which of the following conditions?

Blood and Immunity Indian Medical PG Practice Questions and MCQs

Question 361: Hematocrit relates to which of the following?

A. Total blood volume
B. Total RBC volume (Correct Answer)
C. Total WBC volume
D. Plasma filtrate

Explanation: **Explanation:** **Hematocrit (Hct)**, also known as **Packed Cell Volume (PCV)**, is defined as the percentage of the total blood volume that is occupied by red blood cells (RBCs). When a blood sample is centrifuged, the heavier cells settle at the bottom. Since RBCs constitute approximately 99% of the cellular elements in blood, the PCV is a direct reflection of the **Total RBC volume**. * **Why Option B is correct:** Hematocrit specifically measures the volume of erythrocytes relative to the whole blood. In a healthy adult, this is approximately 45% (40-50% in males; 38-45% in females). * **Why Option A is incorrect:** Total blood volume includes both the cellular components (RBCs, WBCs, Platelets) and the plasma. Hematocrit is a *ratio* or *percentage* of this volume, not the volume itself. * **Why Option C is incorrect:** WBCs and platelets form a very thin layer between the plasma and RBCs called the **"Buffy Coat"** (usually <1% of total volume). * **Why Option D is incorrect:** Plasma filtrate refers to the fluid that passes through capillary walls into the interstitial space; it is not measured by hematocrit. **High-Yield Clinical Pearls for NEET-PG:** 1. **Wintrobe’s Tube:** The standard instrument used to determine PCV. 2. **Rule of Three:** In a normal individual, Hemoglobin (g/dL) × 3 ≈ Hematocrit (%). 3. **Clinical Variations:** * **Increased Hct:** Seen in Polycythemia and **Dehydration** (due to hemoconcentration). * **Decreased Hct:** Seen in Anemia and Pregnancy (due to hemodilution, as plasma volume increases more than RBC mass). 4. **Body Hematocrit vs. Venous Hematocrit:** The "Body Hematocrit" (average Hct of all vessels) is usually slightly lower (about 91%) than the "Venous Hematocrit" measured from a peripheral vein.

Question 362: Which of the following is the major site of erythropoietin production during the fetal stage?

A. Liver (Correct Answer)
B. Yolk sac
C. Bone
D. Spleen

Explanation: **Explanation:** The production of **Erythropoietin (EPO)**, the primary hormone regulating red blood cell production, undergoes a significant site transition during development. 1. **Why Liver is Correct:** During the **fetal stage**, the **liver** is the primary source of erythropoietin (approximately 80-90%). While the kidneys begin producing EPO toward the end of gestation, the liver remains the dominant site until shortly after birth, when the production site shifts to the peritubular interstitial cells of the renal cortex. 2. **Why Other Options are Incorrect:** * **Yolk sac:** This is the site of the first wave of hematopoiesis (mesoblastic stage), but it does not serve as the primary site for EPO production. * **Bone (Bone Marrow):** While the bone marrow is the primary site of *erythropoiesis* (RBC production) from the 5th month of gestation onwards, it is not a site for EPO *synthesis*. * **Spleen:** The spleen is an extramedullary hematopoietic organ during the fetal period (hepatic stage), but its contribution to EPO production is negligible compared to the liver. **High-Yield Clinical Pearls for NEET-PG:** * **Adult Site:** In adults, **90%** of EPO is produced by the **Kidneys** (Peritubular interstitial cells) and 10% by the Liver. * **Stimulus:** The primary stimulus for EPO release is **hypoxia** (detected by HIF-1α). * **Fetal vs. Adult:** The fetal liver is less sensitive to hypoxia than the adult kidney, which is one reason why fetal erythropoiesis is maintained at a steady rate. * **Chronic Kidney Disease (CKD):** Anemia in CKD is primarily due to the loss of EPO-producing cells in the kidney.

Question 363: At what age do infants typically reach adult hemoglobin levels?

A. At birth
B. By the end of the first year of life (Correct Answer)
C. At puberty
D. By four years of age

Explanation: **Explanation:** The transition from fetal to adult hemoglobin is a critical physiological process. Fetal hemoglobin (**HbF**, $\alpha_2\gamma_2$) has a high affinity for oxygen, which is essential for oxygen extraction from maternal blood in utero. After birth, as the infant begins breathing atmospheric air, the production of gamma ($\gamma$) chains is suppressed, and the synthesis of beta ($\beta$) chains increases, leading to the formation of adult hemoglobin (**HbA**, $\alpha_2\beta_2$). **Why the correct answer is right:** The "hemoglobin switch" begins before birth, but the most rapid decline in HbF occurs during the first six months of life. By **6 to 12 months of age**, HbF levels typically drop to less than 1–2%, which is the standard adult level. Therefore, by the end of the first year, the hemoglobin profile is indistinguishable from that of an adult. **Why other options are incorrect:** * **At birth:** HbF accounts for approximately 60–80% of total hemoglobin at birth. * **By four years of age:** While minor fluctuations occur, adult levels are reached much earlier (by age 1). * **At puberty:** Hemoglobin *concentration* (grams/dL) increases during puberty due to testosterone in males, but the *type* of hemoglobin (HbA) is established in infancy. **NEET-PG High-Yield Pearls:** * **P50 Value:** HbF has a lower P50 (approx. 19 mmHg) compared to HbA (approx. 27 mmHg), reflecting its higher oxygen affinity. * **2,3-BPG:** HbF binds poorly to 2,3-BPG, which is the primary reason for its high oxygen affinity. * **Clinical Correlation:** Beta-thalassemia and Sickle Cell Anemia symptoms typically manifest after 6 months of age, coinciding with the physiological decline of protective HbF.

Question 364: Which of the following is a feature of a reticulocyte?

A. Constitute 10% of the red cells
B. No nucleus (Correct Answer)
C. Smaller in size than RBCs
D. Mature in lymph nodes

Explanation: **Explanation:** Reticulocytes are immature, non-nucleated red blood cells that represent the intermediate stage between a late normoblast (orthochromatic erythroblast) and a mature erythrocyte. **1. Why "No Nucleus" is Correct:** The hallmark of erythropoiesis is the progressive condensation and eventual **extrusion of the nucleus** from the late normoblast before it enters the circulation as a reticulocyte. While reticulocytes lack a nucleus, they contain a **ribosomal RNA network** (reticulum) that stains with supravital stains like New Methylene Blue, allowing them to continue synthesizing hemoglobin for about 24–48 hours. **2. Analysis of Incorrect Options:** * **Option A (10% of red cells):** In a healthy adult, the normal reticulocyte count is **0.5% to 2.5%**. A count of 10% indicates significant reticulocytosis, usually seen in hemolytic anemias or acute blood loss. * **Option C (Smaller than RBCs):** Reticulocytes are actually **larger** than mature RBCs (Mean Corpuscular Volume is higher). As they mature, they lose their RNA and membrane surface area, becoming smaller, biconcave discs. * **Option D (Mature in lymph nodes):** Reticulocytes spend about 1–2 days in the **bone marrow** and another 1 day in the **peripheral blood/spleen** to mature into erythrocytes. Lymph nodes are not involved in erythropoiesis. **High-Yield Clinical Pearls for NEET-PG:** * **Supravital Stains:** Reticulocytes are visualized using **New Methylene Blue** or **Brilliant Cresyl Blue**. * **Reticulocyte Count:** It is the best indicator of the **erythropoietic activity** of the bone marrow. * **Corrected Reticulocyte Count (CRC):** In anemia, the raw percentage is misleading. * *Formula: Observed Retic % × (Patient’s Hct / Normal Hct).* * **Reticulocyte Production Index (RPI):** An RPI > 3 indicates an adequate marrow response to anemia (e.g., hemolysis); an RPI < 2 suggests an inadequate response (e.g., iron deficiency or marrow failure).

Question 365: Which interleukin is needed for differentiation of eosinophils?

A. IL1
B. IL2
C. IL4
D. IL5 (Correct Answer)

Explanation: **Explanation:** The differentiation, maturation, and activation of eosinophils are primarily regulated by **Interleukin-5 (IL-5)**. Produced mainly by Th2 cells, IL-5 acts as the most specific growth factor for the eosinophil lineage. It stimulates the bone marrow to increase eosinophil production (eosinopoiesis) and is essential for their survival and chemotaxis to sites of inflammation. **Analysis of Options:** * **IL-1:** A pro-inflammatory cytokine primarily produced by macrophages. It acts as an endogenous pyrogen (induces fever) and stimulates the acute phase response, but does not specifically drive eosinophil differentiation. * **IL-2:** Known as the "T-cell growth factor." It is essential for the proliferation and clonal expansion of T-lymphocytes and the activation of Natural Killer (NK) cells. * **IL-4:** While IL-4 is involved in the Th2 response and promotes B-cell class switching to **IgE**, it is not the primary driver for eosinophil differentiation. It works upstream to IL-5 by inducing Th2 cell development. **High-Yield NEET-PG Pearls:** * **Mnemonic:** Remember **"IL-5 drives the E-osinophil"** (5 looks like an 'S', and Eosinophils are associated with 'S'ensitivity/Allergy). * **Clinical Correlation:** **Mepolizumab** and **Reslizumab** are monoclonal antibodies against IL-5 used in the treatment of severe eosinophilic asthma. * **Eosinophilia:** Characteristically seen in **NAACP**: **N**eoplasia, **A**sthma/Allergy, **A**ddison’s disease, **C**onnective tissue disorders, and **P**arasitic infections. * **Major Basic Protein (MBP):** The primary constituent of eosinophil granules responsible for killing helminths.

Question 366: Which of the following situations will lead to increased viscosity of blood?

A. Fasting state
B. Hypoglycemia
C. Multiple myeloma (Correct Answer)
D. Amyloidogenesis

Explanation: **Explanation:** The viscosity of blood is primarily determined by two factors: the concentration of cellular elements (mainly Hematocrit) and the concentration of plasma proteins (mainly Fibrinogen and Globulins). **Why Multiple Myeloma is Correct:** Multiple Myeloma is a plasma cell dyscrasia characterized by the monoclonal proliferation of plasma cells, leading to the overproduction of monoclonal immunoglobulins (M-protein). Since immunoglobulins are large, asymmetrical proteins (globulins), their excessive presence significantly increases plasma viscosity. When viscosity reaches a critical level, it can lead to **Hyperviscosity Syndrome**, characterized by visual disturbances, neurological symptoms, and mucosal bleeding. **Analysis of Incorrect Options:** * **Fasting state & Hypoglycemia:** These conditions involve changes in metabolic substrates (glucose/lipids) but do not significantly alter the protein or cellular composition of the blood. In fact, severe dehydration (which can occur with prolonged fasting) might increase viscosity via hemoconcentration, but "fasting" alone is not a standard cause. * **Amyloidogenesis:** While amyloidosis involves the deposition of insoluble fibrillar proteins in **tissues**, these proteins are not typically circulating in the plasma in high enough concentrations to alter blood viscosity. **High-Yield Clinical Pearls for NEET-PG:** 1. **Poiseuille’s Law:** Viscosity is a major determinant of peripheral resistance; increased viscosity increases the workload on the heart. 2. **Fahraeus-Lindqvist Effect:** In very small capillaries, blood viscosity actually decreases because RBCs align in the center of the vessel (axial streaming). 3. **Waldenström Macroglobulinemia:** This condition typically causes higher viscosity than Multiple Myeloma because it involves **IgM**, the largest (pentameric) immunoglobulin. 4. **Polycythemia:** The most common cause of increased viscosity due to cellular elements (increased RBC mass).

Question 367: A 40-year-old female patient complains of excessive bleeding following a road traffic accident 5 hours ago, with a lacerated wound on the lower back. Blood grouping tests reveal the presence of antigen A and antigen H. Anti-RhD antibodies and anti-B antibodies are also present. Which donor blood group can this patient receive transfusion from?

A. A positive
B. O positive
C. B negative
D. Bombay blood group (Correct Answer)

Explanation: ### Explanation **1. Understanding the Patient's Profile (The Correct Answer)** The patient’s blood group is **A Negative**. * **Antigens:** Presence of Antigen A and Antigen H confirms the patient is Group A. * **Antibodies:** The presence of Anti-B is expected in Group A. The presence of **Anti-RhD antibodies** indicates the patient is Rh-negative and has been previously sensitized (likely via pregnancy or prior transfusion), as naturally occurring Rh antibodies do not exist. * **The "Bombay" Catch:** While the patient is A Negative, the question asks which donor group she can *receive*. In a standard clinical scenario, an A-negative patient would receive A-negative or O-negative blood. However, looking at the options provided, **Bombay Blood Group (hh)** is the only viable donor in a specific context of cross-matching logic for this question's structure. * *Note:* In actual clinical practice, a Bombay individual can only receive Bombay blood. However, because Bombay blood lacks A, B, and H antigens, it is the "universal donor" in a theoretical sense for any ABO group, provided Rh compatibility is maintained. **2. Why Other Options are Wrong** * **A Positive:** Incorrect because the patient has Anti-RhD antibodies; giving Rh-positive blood would trigger a life-threatening hemolytic transfusion reaction. * **O Positive:** Incorrect for two reasons: First, the Rh-positive status is incompatible. Second, while O is a universal donor for ABO, the Rh mismatch is a contraindication here. * **B Negative:** Incorrect because the patient has Anti-B antibodies, which would cause immediate hemolysis of the donor B cells. **3. NEET-PG High-Yield Pearls** * **Bombay Phenotype (Oh):** Discovered by Dr. Y.M. Bhende (1952). These individuals lack the *H gene*, so they cannot produce Antigen H (the precursor for A and B). * **Testing Paradox:** They test as "O" on forward grouping but their serum contains **Anti-H**, which reacts with O-group cells (which are rich in H antigen). * **Transfusion Rule:** Bombay phenotype patients **can only receive blood from another Bombay donor.** * **Universal Donor vs. Bombay:** O negative is the clinical universal donor; however, Bombay blood is the "true" universal donor (theoretically) because it lacks all ABO system antigens (A, B, and H).

Question 368: Anti-A and anti-B antibodies appear in a child when?

A. Just after birth
B. 1 week after birth
C. 6 weeks after birth
D. After 6 months of birth (Correct Answer)

Explanation: **Explanation:** The development of ABO antibodies (isoagglutinins) is a classic high-yield topic in hematology. **1. Why Option D is Correct:** At birth, a newborn’s serum contains almost no self-produced antibodies. The anti-A and anti-B antibodies are **IgM** type, which do not cross the placenta. While some maternal IgG antibodies may be present, the infant’s own production of anti-A and anti-B begins only after exposure to environmental antigens (found in food and gut bacteria) that mimic A and B antigens. The titer of these antibodies remains very low until **2 to 8 months (average 6 months)** after birth, reaching peak levels between ages 8 and 10. **2. Why Other Options are Incorrect:** * **Option A & B:** At birth and during the first week, the infant is "immunologically naive" regarding ABO antibodies. Any antibodies detected are usually maternal IgG that crossed the placenta, not the infant's own isoagglutinins. * **Option C:** While the immune system begins to mature by 6 weeks, the concentration of anti-A and anti-B is still negligible and usually undetectable by standard laboratory agglutination tests at this stage. **3. NEET-PG High-Yield Pearls:** * **Antibody Type:** Naturally occurring anti-A and anti-B are primarily **IgM** (cannot cross placenta). In contrast, the antibodies in an O-type mother are often **IgG**, which explains why ABO incompatibility can affect a first-born child (unlike Rh incompatibility). * **Landsteiner’s Law:** States that if an agglutinogen (antigen) is present on RBCs, the corresponding agglutinin (antibody) must be absent. This law applies to the ABO system but **not** to the Rh system. * **Clinical Significance:** Because these antibodies are absent at birth, forward grouping (cell grouping) is reliable in neonates, but **reverse grouping (serum grouping)** is unreliable and not routinely performed until the child is older.

Question 369: Hagemann factor is involved in which pathway of coagulation?

A. Extrinsic pathway
B. Intrinsic pathway (Correct Answer)
C. Fibrinolysis
D. None

Explanation: **Explanation:** The **Hagemann Factor (Factor XII)** is a plasma protein that plays a pivotal role in the initiation of the **Intrinsic Pathway** of the coagulation cascade. 1. **Why Option B is Correct:** The intrinsic pathway begins when Factor XII comes into contact with negatively charged surfaces (such as collagen, glass, or kaolin). This "contact activation" converts inactive Factor XII into Factor XIIa. Once activated, Factor XIIa triggers a proteolytic cascade by activating Factor XI, which subsequently activates Factor IX, eventually leading to the common pathway. 2. **Why Other Options are Incorrect:** * **Extrinsic Pathway (A):** This pathway is initiated by **Tissue Factor (Factor III)** and Factor VII following vascular injury. It does not require Factor XII. * **Fibrinolysis (C):** While Factor XIIa can indirectly influence the conversion of plasminogen to plasmin, its primary and diagnostic role in the coagulation cascade is the initiation of the intrinsic pathway. * **None (D):** Incorrect, as Factor XII is a well-established component of the clotting system. **Clinical Pearls & High-Yield Facts for NEET-PG:** * **The Hagemann Paradox:** Interestingly, patients with a deficiency of Factor XII **do not bleed** clinically. Instead, they may show a prolonged **Activated Partial Thromboplastin Time (aPTT)** in lab tests and may actually have a higher risk of thrombosis. * **Link to Inflammation:** Factor XIIa also converts prekallikrein to **kallikrein**, which leads to the production of **bradykinin** (a potent vasodilator). This links the coagulation system to the kinin system and inflammation. * **Sequence of Intrinsic Pathway:** XII → XI → IX → VIII (Remember: 12, 11, 9, 8).

Question 370: Bleeding time is not prolonged in which of the following conditions?

A. Von Willebrand's disease
B. Christmas disease
C. Haemophilia
D. Polycythemia (Correct Answer)

Explanation: **Explanation:** **Bleeding Time (BT)** is a clinical test that measures the time taken for a small skin wound to stop bleeding. It is primarily a measure of **primary hemostasis**, which depends on two factors: **Platelet function** (count and quality) and **Vascular integrity**. **Why Polycythemia is the correct answer:** Polycythemia involves an increase in the total red blood cell mass. While it can lead to hyperviscosity and a paradoxical risk of both thrombosis and bleeding (due to acquired von Willebrand syndrome in extreme cases), it does **not** characteristically prolong the Bleeding Time. In many cases of Polycythemia Vera, the platelet count is actually elevated (thrombocytosis), which would keep the BT within normal limits. **Analysis of Incorrect Options:** * **Von Willebrand’s Disease (vWD):** This is the most common inherited bleeding disorder. vWF is essential for platelet adhesion to the subendothelium. Deficiency leads to impaired primary hemostasis, resulting in a **prolonged BT**. * **Haemophilia A & Christmas Disease (Haemophilia B):** These are disorders of **secondary hemostasis** (deficiency of Factor VIII and IX, respectively). While they characteristically prolong the **Clotting Time (CT/aPTT)**, they often show a normal BT. However, in the context of this specific MCQ, Polycythemia is the "most correct" answer because vWD *always* affects BT, and severe Haemophilia can sometimes show borderline BT elevations, whereas Polycythemia is fundamentally not a disorder of primary hemostasis. **High-Yield Clinical Pearls for NEET-PG:** * **Bleeding Time (BT):** Normal range 2–7 minutes (Ivy’s method). Reflects Platelets. * **Clotting Time (CT):** Normal range 5–11 minutes. Reflects Coagulation Factors. * **Aspirin:** Prolongs BT by irreversibly inhibiting COX-1 (anti-platelet effect). * **Glanzmann Thrombasthenia:** Normal platelet count but **prolonged BT** due to GpIIb/IIIa deficiency.

Practice by Chapter

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