Blood and Immunity Practice Questions

Q: Kupffer cells are a type of?

Macrophages. **Explanation:** **Kupffer cells** are specialized, resident **macrophages** located within the sinusoids of the liver. They form part of the **Mononuclear Phagocyte System (MPS)**. Their primary function is to filter the portal blood, removing bacteria, cellular debris, and aged red blood cells through phagocytosis. They also play a crucial role in innate immunity and iron metabolism by recycling hemoglobin. **Analysis of Options:** * **Option A (Dendritic cells):** While both are antigen-presenting cells (APCs), dendritic cells are specialized for initiating adaptive immune responses by migrating to lymph nodes. Kupffer cells remain stationary in the liver sinusoids. * **Option C & D (B and T cells):** These are **lymphocytes** involved in adaptive immunity. B cells produce antibodies, and T cells are involved in cell-mediated immunity. They are not phagocytic cells like Kupffer cells. **High-Yield NEET-PG Pearls:** * **Location:** They are found on the luminal surface of the endothelial cells in the **hepatic sinusoids**. * **Origin:** Like all macrophages, they originate from **monocytes** (derived from bone marrow hematopoietic stem cells). * **Staining:** They can be visualized using **India ink** or specialized markers like **CD68**. * **Other Tissue-Specific Macrophages (Commonly Tested):** * **CNS:** Microglia * **Lungs:** Alveolar macrophages (Dust cells) * **Skin:** Langerhans cells * **Bone:** Osteoclasts * **Kidney:** Mesangial cells

Q: All statements about lactoferrin are true, except?

It transports iron for erythropoiesis.. ### Explanation Lactoferrin is a multifunctional iron-binding glycoprotein belonging to the transferrin family. Its primary role is **bacteriostatic**—it sequesters free iron, making it unavailable for bacterial growth. **Why Option D is the Correct Answer (The False Statement):** While lactoferrin has a high affinity for iron, it **does not** transport iron for erythropoiesis. That function is exclusively performed by **Transferrin**. Lactoferrin actually competes with bacteria for iron and helps in the sequestration of iron into the Reticuloendothelial System (RES) during inflammation, which is a contributing factor to the "Anemia of Chronic Disease." **Analysis of Other Options:** * **Option A:** Lactoferrin is a major constituent of the **secondary (specific) granules** of neutrophils. It is released into the phagosome and extracellular space during degranulation to inhibit microbial proliferation. * **Option B:** It is found in high concentrations in **exocrine secretions** such as breast milk (highest in colostrum), tears, nasal secretions, saliva, and gastrointestinal mucus, serving as a first-line innate immune defense. * **Option C:** Lactoferrin has an iron-binding affinity approximately **250 times higher** than that of serum transferrin, allowing it to retain iron even at the low pH levels typical of infection sites. ### High-Yield NEET-PG Pearls * **Marker of Inflammation:** Fecal lactoferrin is a sensitive marker used to differentiate Inflammatory Bowel Disease (IBD) from Irritable Bowel Syndrome (IBS). * **Bacteriostatic vs. Bactericidal:** It is bacteriostatic by iron deprivation, but can be bactericidal by directly binding to bacterial lipopolysaccharides (LPS) and disrupting cell membranes. * **Neutrophil Granules:** Remember: Primary granules contain **Myeloperoxidase (MPO)**; Secondary granules contain **Lactoferrin** and **Alkaline Phosphatase**.

Q: Pre-B cells and B cells are produced in which location?

Bone marrow. **Explanation:** The correct answer is **Bone marrow**. In humans, the bone marrow serves as the primary lymphoid organ where B-cell lymphopoiesis occurs throughout life. **Why Bone Marrow is Correct:** The development of B cells is a multi-step process that begins with hematopoietic stem cells. These differentiate into **Pro-B cells**, then **Pre-B cells** (characterized by the presence of cytoplasmic $\mu$ heavy chains), and finally into **immature B cells** (expressing surface IgM). All these stages occur within the microenvironment of the **bone marrow**. Once they express surface IgM and IgD, they become mature (but naive) B cells and migrate to peripheral lymphoid organs. **Why Other Options are Incorrect:** * **Thymus:** This is the primary lymphoid organ for **T-cell** maturation. While T-cell precursors originate in the bone marrow, they must migrate to the thymus to undergo TCR rearrangement and selection. * **Tonsils & GALT:** These are **secondary lymphoid organs**. They are sites where mature B cells encounter antigens, undergo clonal expansion, and perform effector functions (like isotype switching). They do not produce B cells from precursors. **High-Yield NEET-PG Pearls:** * **B-cell maturation site:** Bone marrow (Mnemonic: **B**-cell = **B**one marrow). * **T-cell maturation site:** Thymus (Mnemonic: **T**-cell = **T**hymus). * **Bursa of Fabricius:** In birds, B cells mature in this specialized organ; in humans, the bone marrow is the functional equivalent. * **Negative Selection:** Immature B cells that recognize "self" antigens in the bone marrow are eliminated via apoptosis or undergo **receptor editing** to prevent autoimmunity.

Q: Platelet activation includes:

All of the above. **Explanation:** Platelet activation is a complex, multi-step process essential for **primary hemostasis**. When a blood vessel is injured, platelets undergo a series of rapid functional changes to form a temporary hemostatic plug. 1. **Adhesion (Option A):** This is the initial step. Platelets adhere to the exposed subendothelial collagen. This process is primarily mediated by **von Willebrand Factor (vWF)**, which acts as a bridge between the subendothelial collagen and the platelet surface receptor **Glycoprotein Ib/IX/V (GpIb/IX/V)**. 2. **Secretion/Release Reaction (Option B):** Once adhered, platelets become activated and change shape. They release the contents of their granules: * **Alpha granules:** Contain Fibrinogen, vWF, and Platelet-Derived Growth Factor (PDGF). * **Dense granules:** Contain **ADP**, Calcium, and Serotonin (mnemonic: **SAC**). ADP and Thromboxane A2 (TxA2) further recruit and activate more platelets. 3. **Aggregation (Option C):** This is the final step of activation where platelets stick to each other. ADP and TxA2 cause a conformational change in the **GpIIb/IIIa** receptors, allowing them to bind to **Fibrinogen**, which links multiple platelets together to form the plug. Since all three processes—Adhesion, Secretion, and Aggregation—are integral components of the platelet activation sequence, **Option D** is the correct answer. **High-Yield Clinical Pearls for NEET-PG:** * **Bernard-Soulier Syndrome:** Deficiency of **GpIb** (Defect in Adhesion). * **Glanzmann Thrombasthenia:** Deficiency of **GpIIb/IIIa** (Defect in Aggregation). * **Aspirin:** Irreversibly inhibits Cyclooxygenase-1 (COX-1), preventing the synthesis of **Thromboxane A2**, thereby inhibiting platelet aggregation. * **vWF:** Synthesized in endothelial cells (stored in **Weibel-Palade bodies**) and megakaryocytes.

Q: Which of the following is NOT a function of CD4+ T cells?

Immunoglobulin production. The question asks for the function **NOT** performed by CD4+ T cells (Helper T cells). **Why Option B is correct:** **Immunoglobulin (antibody) production** is the primary function of **Plasma cells**, which are differentiated **B-lymphocytes**. While CD4+ T cells (specifically the Th2 subset) are essential for stimulating B cells to undergo class switching and maturation via cytokine secretion (like IL-4 and IL-5) [1], [2], they do not produce antibodies themselves. **Analysis of Incorrect Options:** * **A. Memory cell formation:** After an immune response, a subset of activated CD4+ T cells differentiates into long-lived **Memory T cells**. these provide a rapid response upon re-exposure to the same antigen. * **C. Macrophage activation:** This is a hallmark function of **Th1 cells** (a subset of CD4+ cells). They secrete **Interferon-gamma (IFN-γ)**, which enhances the microbicidal activity of macrophages to destroy intracellular pathogens like *M. tuberculosis* [2]. * **D. Cytotoxicity:** While classically attributed to CD8+ T cells, a specific subset known as **CD4+ Cytotoxic T Lymphocytes (CTLs)** can directly kill target cells via granzyme and perforin pathways, particularly in viral infections and antitumor responses. **High-Yield Clinical Pearls for NEET-PG:** * **MHC Restriction:** CD4+ cells recognize antigens presented by **MHC Class II** molecules (Rule of 8: 4 × 2 = 8). * **HIV Pathogenesis:** The hallmark of HIV/AIDS is the progressive depletion of **CD4+ T cells**, leading to opportunistic infections. * **Th1 vs. Th2:** Th1 cells produce IL-2 and IFN-γ (Cell-mediated immunity); Th2 cells produce IL-4, IL-5, and IL-13 (Humoral immunity/Allergy) [2].

Q: In a person weighing 100 Kgs, what is the estimated blood volume?

8 L. **Explanation:** The correct answer is **8 L**. The total blood volume (TBV) in a healthy adult is approximately **7% to 8% of the total body weight**. For a person weighing 100 kg, the calculation is: $100\text{ kg} \times 0.08 (8\%) = 8\text{ Liters}$. **Why other options are incorrect:** * **A (5 L):** This is the average blood volume for a standard **70 kg male** ($70 \times 0.07 = 4.9\text{ L}$). It is the most common "textbook" value but does not apply to a 100 kg individual. * **B (6 L):** This represents roughly 6% of the body weight for a 100 kg person, which is slightly below the physiological norm for an average adult. * **D (10 L):** This would represent 10% of the body weight. While blood volume can increase in certain states (like pregnancy), 10% is significantly higher than the normal physiological range for a healthy adult. **High-Yield Clinical Pearls for NEET-PG:** 1. **Volume Distribution:** Roughly 55% of blood is Plasma, and 45% is Formed Elements (Hematocrit). 2. **Gender Variation:** Females typically have a slightly lower blood volume per kg (~65-70 ml/kg) compared to males (~70-75 ml/kg) due to a higher percentage of body fat. 3. **Measurement:** The "Gold Standard" for measuring plasma volume is **Evans Blue dye (T-1824)** or **Radio-iodinated albumin**, while RBC volume is measured using **Chromium-51 ($^{51}\text{Cr}$)** labeled RBCs. 4. **Blood Reservoir:** The **systemic veins and venules** contain the largest portion of blood volume (~64%) at any given time, acting as the body's blood reservoir.

Q: Von Willebrand factor is produced by which of the following?

Platelets. **Explanation:** Von Willebrand Factor (vWF) is a large multimeric glycoprotein essential for primary hemostasis. It is synthesized and stored in two specific locations: 1. **Endothelial Cells:** Stored in specialized organelles called **Weibel-Palade bodies**. 2. **Platelets:** Stored in the **$\alpha$-granules** (alpha-granules). When a blood vessel is injured, vWF is released to act as a "molecular bridge" between the exposed subendothelial collagen and the **GpIb receptor** on platelets, facilitating platelet adhesion. **Analysis of Options:** * **Option B (Correct):** Platelets produce and store vWF in their $\alpha$-granules. Upon activation, they release vWF to promote further platelet recruitment and stabilize Factor VIII. * **Option A (Incorrect):** While the **liver** synthesizes most coagulation factors (like Factor II, VII, IX, X, and Fibrinogen), it does **not** produce vWF. This is a common distractor; remember that vWF is the exception to the "liver produces clotting factors" rule. * **Option C & D (Incorrect):** Neither the lungs nor the spleen are primary sites for vWF synthesis. The spleen primarily functions in the sequestration and destruction of old platelets, rather than the production of vWF. **High-Yield Clinical Pearls for NEET-PG:** * **Dual Function:** vWF facilitates platelet adhesion (via GpIb) and acts as a carrier protein to stabilize **Factor VIII** in circulation, preventing its rapid degradation. * **vWD (Von Willebrand Disease):** The most common inherited bleeding disorder. It typically presents with mucosal bleeding and a prolonged **Bleeding Time (BT)**. * **Diagnostic Marker:** Factor VIII levels are often low in vWD because vWF is not available to protect it. * **Desmopressin (DDAVP):** Used in treatment as it triggers the release of vWF from endothelial Weibel-Palade bodies.

Q: Which coagulation factor is not freely circulating in the blood?

Factor 3. **Explanation:** The correct answer is **Factor 3 (Tissue Factor/Thromboplastin)**. **Why Factor 3 is the correct answer:** Unlike most clotting factors, which are proenzymes synthesized by the liver and secreted into the plasma to circulate freely, **Factor 3 (Tissue Factor)** is a cell-surface glycoprotein. It is constitutively expressed on the adventitia of blood vessels and in the membranes of extravascular cells (like fibroblasts). It only comes into contact with blood following **vascular injury**. Once exposed, it binds to Factor VIIa to initiate the **Extrinsic Pathway** of coagulation. Because it is structurally bound to cell membranes, it does not circulate freely in the blood under physiological conditions. **Why the other options are incorrect:** * **Factor 9 (Christmas Factor):** A vitamin K-dependent serine protease that circulates freely in the plasma. It is a key component of the intrinsic pathway. * **Factor 10 (Stuart-Prower Factor):** A vitamin K-dependent factor that circulates freely. It is the first factor of the **Common Pathway**, where it is activated to Xa. * **Factor 12 (Hageman Factor):** A plasma protein that circulates freely. it is activated upon contact with negatively charged surfaces (like collagen or glass), initiating the intrinsic pathway. **High-Yield Clinical Pearls for NEET-PG:** * **Factor 4:** Refers to **Calcium ions (Ca²⁺)**, which are essential for almost all steps of the coagulation cascade except the initial stages of the intrinsic pathway. * **Labile Factor:** Factor 5 (activity decreases quickly in stored blood). * **Stable Factor:** Factor 7 (has the shortest half-life among all factors). * **Hageman Factor (F12) Deficiency:** Unique because it causes a prolonged aPTT in vitro but does **not** cause clinical bleeding in vivo.

Question 1

A 24-year-old man presents with a broken leg. An initial blood test reveals a WBC count of 22 x 10^3/ml. Five hours later, a repeat blood test shows a WBC count of 7 x 10^3/ml. What is the most likely cause of the elevated WBC count in the initial test?

Accepted Answer

Release of pre-formed, mature WBCs into the circulation

Answer

Increased production of WBCs by the bone marrow

Answer

Decreased destruction of WBCs

Answer

Increased production of selectins

Question 2

Kupffer cells are a type of?

Accepted Answer

Macrophages

Answer

Dendritic cells

Answer

B cells

Answer

T cells

Question 3

What is the best index of platelet function?

Accepted Answer

Clot retraction time

Answer

Bleeding time

Answer

Clotting time

Answer

Prothrombin time

Question 4

All statements about lactoferrin are true, except?

Accepted Answer

It transports iron for erythropoiesis.

Answer

It is present in the secondary granules of neutrophils.

Answer

It is present in exocrine secretions of the body.

Answer

It has a great affinity for iron.

Question 5

Pre-B cells and B cells are produced in which location?

Accepted Answer

Bone marrow

Answer

Thymus

Answer

Tonsils

Answer

Gut associated lymphoid tissue

Question 6

Platelet activation includes:

Accepted Answer

All of the above

Answer

Adhesion

Answer

Secretion

Answer

Aggregation

Question 7

Which of the following is NOT a function of CD4+ T cells?

Accepted Answer

Immunoglobulin production

Answer

Memory cell formation

Answer

Macrophage activation

Answer

Cytotoxicity

Question 8

In a person weighing 100 Kgs, what is the estimated blood volume?

Accepted Answer

8 L

Answer

5 L

Answer

6 L

Answer

10 L

Question 9

Von Willebrand factor is produced by which of the following?

Accepted Answer

Platelets

Answer

Liver

Answer

Lungs

Answer

Spleen

Question 10

Which coagulation factor is not freely circulating in the blood?

Accepted Answer

Factor 3

Answer

Factor 9

Answer

Factor 10

Answer

Factor 12

Blood and Immunity — MCQs

Blood and Immunity — MCQs

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