Blood and Immunity Practice Questions

Q: Rh antibodies are:

IgM. **Explanation:** The correct answer is **A. IgM**. **Medical Concept:** Rh antibodies are primarily produced following exposure to Rh-positive red blood cells in an Rh-negative individual (isoimmunization). The **initial immune response** (primary response) to the D-antigen results in the production of **IgM** antibodies. These are pentameric, large molecules that do not cross the placenta. However, upon subsequent exposure or as the immune response matures (secondary response), the body undergoes class switching to produce **IgG** antibodies. While clinical complications like Hemolytic Disease of the Newborn (HDN) are caused by IgG (which crosses the placenta), the fundamental physiological classification of the initial Rh antibody formed is IgM. **Analysis of Incorrect Options:** * **B. IgA:** Found primarily in secretions (colostrum, saliva, tears) and mucosal surfaces; it is not involved in Rh incompatibility. * **C. IgE:** Mediates Type I hypersensitivity reactions (allergies) and defense against helminthic parasites. * **D. IgD:** Primarily acts as an antigen receptor on the surface of B-lymphocytes; its role in serum is minimal and unrelated to blood group antigens. **High-Yield NEET-PG Pearls:** * **ABO Antibodies:** Naturally occurring, predominantly **IgM** (cannot cross placenta). * **Rh Antibodies:** Immune-mediated, initially **IgM**, then predominantly **IgG** (can cross placenta). * **Anti-D (RhoGAM):** Given to Rh-negative mothers to prevent sensitization; it is an IgG preparation that destroys fetal Rh+ cells before the mother's immune system can react. * **Direct Coombs Test:** Detects antibodies already bound to the surface of RBCs (used to diagnose HDN).

Q: All of the following stem cell populations are found within the bone marrow, except?

Myoblast Progenitor cells. ### Explanation The bone marrow is a complex microenvironment (niche) that serves as the primary site for hematopoiesis and houses various multipotent stem cell populations. **Why Myoblast Progenitor Cells are the Correct Answer:** **Myoblast progenitor cells** (satellite cells) are the precursors to skeletal muscle fibers. They are found located between the sarcolemma and the basal lamina of **muscle fibers**, not in the bone marrow. Their primary role is the repair and regeneration of muscle tissue following injury. **Analysis of Incorrect Options:** * **Hematopoietic Stem Cells (HSCs):** These are the most well-known residents of the bone marrow. They are multipotent cells responsible for the constant production of all blood cell lineages (RBCs, WBCs, and platelets). * **Mesenchymal Stem Cells (MSCs):** Also known as marrow stromal cells, these are multipotent cells that can differentiate into non-hematopoietic lineages, including **osteoblasts** (bone), **chondrocytes** (cartilage), and **adipocytes** (fat). * **Endothelial Progenitor Cells (EPCs):** These cells reside in the bone marrow and can be mobilized into the circulation to participate in angiogenesis and the repair of blood vessel linings. **High-Yield Clinical Pearls for NEET-PG:** * **Niche Concept:** The bone marrow "niche" consists of cellular components (osteoblasts, endothelial cells) and humoral factors (CXCL12/SDF-1) that regulate stem cell quiescence and proliferation. * **CD Markers:** HSCs are typically identified by the presence of **CD34+** and **CD117+ (c-kit)**, and the absence of lineage-specific markers (Lin-). * **Transdifferentiation:** While MSCs primarily form bone/cartilage/fat, they are a major focus of regenerative medicine due to their potential to differentiate into various tissues under specific experimental conditions.

Q: Which of the following cell types are classified as large granular lymphocytes?

NK cells. **Explanation:** **Natural Killer (NK) cells** are the correct answer because they are morphologically defined as **Large Granular Lymphocytes (LGLs)**. Unlike small lymphocytes (B and T cells), NK cells possess a more abundant cytoplasm containing prominent azurophilic granules. These granules house cytotoxic proteins like **perforins and granzymes**, which are essential for the innate immune response against virally infected cells and tumor cells. **Analysis of Incorrect Options:** * **B cells and T cells (Options A & C):** These are typically classified as **small, non-granular lymphocytes**. They have a high nuclear-to-cytoplasmic ratio with very little cytoplasm and generally lack visible granules under light microscopy. While a small subset of T cells (specifically activated CD8+ T cells) can exhibit an LGL morphology, the classic and primary definition of an LGL refers to NK cells. * **Plasma cells (Option D):** These are terminally differentiated B cells. Morphologically, they are characterized by an eccentric "cartwheel" nucleus and a prominent perinuclear clear zone (Golgi apparatus), but they are not classified as large granular lymphocytes. **High-Yield Pearls for NEET-PG:** * **Surface Markers:** NK cells are identified by the presence of **CD56 and CD16**, and the absence of CD3 (T-cell marker). * **Function:** They provide the first line of defense and do not require prior sensitization (MHC-independent killing). * **Clinical Correlation:** **LGL Leukemia** is a rare lymphoproliferative disorder that can arise from either NK cells or T cells, often presenting with neutropenia and splenomegaly. * **Chediak-Higashi Syndrome:** A condition where NK cell function is impaired due to defective granule formation/trafficking.

Q: Protein C activation causes which of the following?

Inactivation of factor V. **Explanation:** Protein C is a vitamin K-dependent plasma protein that serves as a natural anticoagulant. Its activation is triggered when **Thrombin** binds to **Thrombomodulin** on the endothelial cell surface. Once activated (forming Activated Protein C or APC), it works alongside its cofactor, **Protein S**, to maintain blood fluidity. **Why Option D is Correct:** Activated Protein C (APC) exerts its anticoagulant effect by proteolytically **inactivating Factors Va and VIIIa**. These factors are essential cofactors in the coagulation cascade: Factor Va is required for the prothrombinase complex (to form thrombin), and Factor VIIIa is required for the intrinsic tenase complex. By inactivating them, Protein C effectively shuts down the amplification of the clotting cascade. **Why Other Options are Incorrect:** * **Option A:** Protein C is an **anticoagulant**, meaning it inhibits clotting rather than promoting it. * **Option B:** Factor II (Prothrombin) is inactivated by direct thrombin inhibitors (like Heparin/Antithrombin III), not by Protein C. * **Option C:** Factor X is an enzyme in the common pathway; Protein C inhibits the *cofactors* (V and VIII) that help activate Factor X, rather than activating it. **NEET-PG High-Yield Pearls:** * **Factor V Leiden:** The most common inherited cause of hypercoagulability (thrombophilia). It involves a mutation in Factor V that makes it **resistant** to inactivation by Protein C. * **Warfarin-Induced Skin Necrosis:** Since Protein C has a shorter half-life than other clotting factors (II, VII, IX, X), starting Warfarin can cause a transient pro-coagulant state, leading to microvascular thrombosis and skin necrosis. * **Mnemonic:** Protein **C** and **S** **C**ut **S**tops (they cut/inactivate the cofactors to stop clotting).

Q: A patient with blood group O can safely receive plasma from which blood group donor?

Group A, B, and AB. ### Explanation The core concept in transfusion medicine is understanding the difference between **Whole Blood/Packed Red Blood Cell (PRBC)** transfusion and **Plasma** transfusion. **1. The Underlying Medical Concept:** * **PRBC Transfusion:** We worry about the **antigens** on the donor's RBCs and the **antibodies** in the recipient's plasma. * **Plasma Transfusion:** We worry about the **antibodies** present in the donor's plasma and how they will react with the **antigens** on the recipient's RBCs. A patient with **Blood Group O** has **no A or B antigens** on their red blood cells. Because there are no antigens for antibodies to attack, they can safely receive plasma containing Anti-A antibodies (from Group B), Anti-B antibodies (from Group A), or both. Therefore, plasma from A, B, or AB donors will not cause hemolysis in a Group O recipient. **2. Analysis of Options:** * **Options A & B:** While Group O can receive plasma from A or B, these options are "incomplete." Since Group O RBCs lack antigens, they are compatible with plasma from any group. * **Option C:** Group AB plasma is the "Universal Donor" for plasma because it contains **no antibodies**. While safe, it is not the *only* safe option for a Group O recipient. * **Option D (Correct):** Since Group O RBCs are "antigen-neutral," they are compatible with any plasma regardless of the antibody content. **3. NEET-PG High-Yield Pearls:** * **Universal Donor (RBCs):** Group O Negative (No antigens). * **Universal Recipient (RBCs):** Group AB Positive (No antibodies). * **Universal Donor (Plasma):** Group AB (No antibodies in plasma). * **Universal Recipient (Plasma):** Group O (No antigens on RBCs to be attacked). * **Landsteiner’s Law:** States that if an antigen is present on RBCs, the corresponding antibody must be absent in the plasma (and vice versa). This law does not apply to Group AB (no antibodies) or Group O (no antigens).

Q: Thrombomodulin I is produced by all of the following EXCEPT?

Cerebral circulation. **Explanation:** Thrombomodulin is a high-affinity transmembrane receptor for thrombin, primarily expressed on the surface of vascular endothelial cells. Its primary physiological role is to convert thrombin from a procoagulant enzyme into an anticoagulant activator. When thrombin binds to thrombomodulin, it activates **Protein C**, which then inactivates Factors Va and VIIIa, thereby inhibiting clot formation. **Why Cerebral Circulation is the Correct Answer:** While thrombomodulin is expressed by the endothelium of most blood vessels throughout the body (including the splanchnic, skin, and muscle beds), it is **notably absent or expressed at extremely low levels** in the microvasculature of the **brain (cerebral circulation)**. This regional deficiency is a critical physiological feature; it is believed that the brain relies on different mechanisms for hemostasis, and the lack of thrombomodulin may contribute to the high risk of fibrin deposition and thrombosis in certain cerebrovascular pathologies. **Analysis of Incorrect Options:** * **Splanchnic, Skin, and Muscle circulation:** These are major systemic vascular beds where endothelial cells express high levels of thrombomodulin to maintain a thromboresistant surface and prevent intravascular coagulation under normal physiological conditions. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Thrombin + Thrombomodulin complex → Activates Protein C → Inactivates Factors Va & VIIIa (with Protein S as a cofactor). * **Soluble Thrombomodulin:** Can be measured in plasma as a marker of widespread endothelial damage (e.g., in DIC or severe sepsis). * **Location Exception:** Remember that the **Cerebral microvessels** and the **Placental syncytiotrophoblasts** (in specific contexts) are the high-yield exceptions regarding standard endothelial expression patterns.

Q: What is the half-life of factor VIII?

8-12 hours. ### Explanation **Correct Answer: B. 8-12 hours** **Medical Concept:** Factor VIII (Anti-hemophilic factor) is a critical glycoprotein in the intrinsic pathway of the coagulation cascade. It acts as a cofactor for Factor IXa in the activation of Factor X. In the circulation, Factor VIII is non-covalently bound to **von Willebrand Factor (vWF)**, which stabilizes it and protects it from rapid proteolytic degradation. The biological half-life of Factor VIII in a healthy individual is typically **8 to 12 hours**. This duration is clinically significant as it dictates the dosing frequency (usually twice daily) for replacement therapy in patients with Hemophilia A. **Analysis of Incorrect Options:** * **A. 2-4 hours:** This is too short for Factor VIII. However, the half-life of Factor VII (the shortest of all clotting factors) is approximately 4–6 hours. * **C. 6 minutes:** This is extremely short and does not correspond to any major clotting factor. For comparison, the half-life of Epinephrine in plasma is roughly 1–3 minutes. * **D. 60 days:** This is far too long for plasma proteins. This duration is more characteristic of the lifespan of certain cells or the half-life of specific drugs/isotopes. **High-Yield Clinical Pearls for NEET-PG:** * **Shortest Half-life:** Factor VII (4–6 hours). This is why the Prothrombin Time (PT) is the first to prolong in acute liver failure or Vitamin K deficiency. * **Longest Half-life:** Factor XIII (approx. 5–10 days) or Fibrinogen (3–5 days). * **Site of Synthesis:** Unlike most clotting factors synthesized solely in the liver, Factor VIII is primarily produced in the **sinusoidal endothelial cells** of the liver and extrahepatic endothelial cells. * **Hemophilia A:** An X-linked recessive deficiency of Factor VIII. Replacement therapy aims to maintain trough levels above 1% to prevent spontaneous bleeding.

Q: The eosinophil count in the peripheral blood smear is increased in which of the following conditions?

Allergic conditions. **Explanation:** **1. Why Allergic Conditions is Correct:** Eosinophilia (increased eosinophil count) is a hallmark of Type I hypersensitivity reactions and parasitic infections. In **allergic conditions** (such as bronchial asthma, hay fever, and urticaria), mast cells and basophils release **Eosinophil Chemotactic Factor of Anaphylaxis (ECF-A)**. This attracts eosinophils to the site of inflammation. Eosinophils then release enzymes like histaminase and arylsulfatase to degrade inflammatory mediators (histamine and leukotrienes), acting as a "modulator" to limit the allergic response. **2. Why Other Options are Incorrect:** * **Anaemia:** This refers to a decrease in red blood cell count or hemoglobin levels. It does not typically affect the differential leukocyte count unless it is part of a broader bone marrow pathology (like aplastic anemia, which causes pancytopenia). * **Polycythemia:** This is an increase in the total red blood cell mass. While Polycythemia Vera (a myeloproliferative disorder) may show a general increase in all cell lines (panmyelosis), it is not a specific cause for isolated eosinophilia. * **Typhoid Fever:** Classically, typhoid fever is associated with **eosinopenia** (disappearance of eosinophils) and leukopenia. The return of eosinophils in a typhoid patient is often considered a sign of recovery. **High-Yield Clinical Pearls for NEET-PG:** * **Normal Eosinophil Count:** 1–4% of total WBC count (approx. 150–450 cells/µL). * **Causes of Eosinophilia (Mnemonic: NAACP):** **N**eoplasm, **A**llergy (Asthma), **A**ddison’s disease, **C**onnective tissue disorders (Churg-Strauss), **P**arasitic infections (Strongyloides, Ascariasis). * **Eosinopenia:** Occurs during acute stress, Cushing’s syndrome, and administration of **ACTH or Corticosteroids** (which sequester eosinophils in the lungs and spleen).

Q: Which of the following cells is derived from the colony-forming unit-erythroid (CFU-E)?

Red blood cell. **Explanation:** The process of hematopoiesis begins with the **Pluripotent Hematopoietic Stem Cell (PHSC)**, which differentiates into two main lineages: the Common Lymphoid Progenitor and the **Common Myeloid Progenitor (CMP)**. **1. Why Red Blood Cell is Correct:** The CMP further differentiates into the **CFU-GEMM** (Granulocyte, Erythrocyte, Monocyte, Megakaryocyte) lineage. From here, the erythroid line progresses as follows: * **BFU-E** (Burst-Forming Unit-Erythroid): The earliest committed erythroid precursor. * **CFU-E** (Colony-Forming Unit-Erythroid): Derived from BFU-E, these cells are highly sensitive to **Erythropoietin (EPO)**. * CFU-E then matures into the **Proerythroblast**, which eventually leads to the formation of the mature **Red Blood Cell (Erythrocyte)**. **2. Why Other Options are Incorrect:** * **Lymphocytes:** Derived from the **Common Lymphoid Progenitor (CLP)**, not the myeloid line. * **Platelets:** Derived from **CFU-Meg** (Megakaryocyte), which matures into megakaryocytes that fragment into platelets. * **Neutrophils:** Derived from **CFU-GM** (Granulocyte-Monocyte) and subsequently **CFU-G**. **NEET-PG High-Yield Pearls:** * **Erythropoietin (EPO)** primarily acts on the **CFU-E** stage to stimulate proliferation and prevent apoptosis. * The **Proerythroblast** is the first morphologically identifiable cell in the erythroid series. * **Reticulocytes** are the immediate precursors to mature RBCs; an elevated reticulocyte count indicates active bone marrow erythropoiesis (e.g., in hemolytic anemia). * The transition from Proerythroblast to mature RBC takes approximately **7 days**.

Question 1

Rh antibodies are:

Accepted Answer

IgM

Answer

IgA

Answer

IgE

Answer

IgD

Question 2

All of the following stem cell populations are found within the bone marrow, except?

Accepted Answer

Myoblast Progenitor cells

Answer

Endothelial Progenitor cells

Answer

Mesenchymal stem cells

Answer

Hematopoietic stem cells

Question 3

Which of the following cell types are classified as large granular lymphocytes?

Accepted Answer

NK cells

Answer

B cells

Answer

T cells

Answer

Plasma cells

Question 4

Protein C activation causes which of the following?

Accepted Answer

Inactivation of factor V

Answer

Promotion of clotting

Answer

Inactivation of factor II

Answer

Activation of factor X

Question 5

A patient with blood group O can safely receive plasma from which blood group donor?

Accepted Answer

Group A, B, and AB

Answer

Group A only

Answer

Group B only

Answer

Group AB only

Question 6

Thrombomodulin I is produced by all of the following EXCEPT?

Accepted Answer

Cerebral circulation

Answer

Splanchnic circulation

Answer

Skin circulation

Answer

Muscle circulation

Question 7

What is the half-life of factor VIII?

Accepted Answer

8-12 hours

Answer

2-4 hours

Answer

6 minutes

Answer

60 days

Question 8

All endothelial cells produce thrombomodulin except those found in which circulation?

Accepted Answer

Cerebral circulation

Answer

Hepatic circulation

Answer

Cutaneous circulation

Answer

Renal circulation

Question 9

The eosinophil count in the peripheral blood smear is increased in which of the following conditions?

Accepted Answer

Allergic conditions

Answer

Anaemia

Answer

Polycythemia

Answer

Typhoid fever

Question 10

Which of the following cells is derived from the colony-forming unit-erythroid (CFU-E)?

Accepted Answer

Red blood cell

Answer

Lymphocyte

Answer

Platelet

Answer

Neutrophil

Blood and Immunity — MCQs

Blood and Immunity — MCQs

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