Blood and Immunity Practice Questions

Q: Plasma cells are derived from which of the following cell types?

B lymphocytes. **Explanation:** **1. Why B lymphocytes is correct:** Plasma cells are the final functional stage of B cell differentiation. When a **B lymphocyte** encounters a specific antigen and receives signals from helper T cells, it undergoes activation, proliferation, and differentiation. This process transforms the B cell into a **plasma cell**, which acts as an "antibody factory." These cells possess an extensive rough endoplasmic reticulum (RER) to synthesize and secrete large quantities of immunoglobulins (antibodies) into the blood and lymph. **2. Why other options are incorrect:** * **T lymphocytes:** These are responsible for cell-mediated immunity. They differentiate into Helper T cells (CD4+), Cytotoxic T cells (CD8+), or Regulatory T cells, but they never produce antibodies or transform into plasma cells. * **NK cells:** These are large granular lymphocytes that form part of the innate immune system. They kill virally infected or tumor cells directly without prior sensitization and do not differentiate into plasma cells. * **Monocytes:** These are myeloid lineage cells that circulate in the blood and migrate into tissues to differentiate into **macrophages** or dendritic cells, primarily functioning in phagocytosis and antigen presentation. **3. High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** Plasma cells have a characteristic **"Cartwheel" or "Clock-face" appearance** of chromatin in the nucleus and a prominent perinuclear halo (Golgi apparatus). * **Multiple Myeloma:** A plasma cell dyscrasia (malignancy) characterized by the "M-spike" on protein electrophoresis and **Bence-Jones proteins** in urine. * **Russell Bodies:** These are eosinophilic inclusions found in plasma cells representing overloaded immunoglobulin secretions. * **Surface Markers:** While B cells express CD19 and CD20, mature plasma cells typically lose these and express **CD138** (Syndecan-1).

Q: Glucocorticoids lead to an increase in blood levels of which of the following?

Neutrophils. **Explanation:** Glucocorticoids (like cortisol) have a profound effect on the distribution and count of white blood cells in the peripheral blood. **Why Neutrophils increase (Correct Answer):** Glucocorticoids cause **Neutrophilia** primarily through a process called **demargination**. Normally, a significant portion of neutrophils is "marginated" (adhered to the endothelial walls of blood vessels). Glucocorticoids decrease the expression of adhesion molecules (like L-selectin), causing these cells to detach into the main bloodstream. Additionally, they stimulate the release of mature neutrophils from the bone marrow and inhibit their migration into tissues, leading to an overall rise in the peripheral neutrophil count. **Why other options are incorrect:** Glucocorticoids are generally **immunosuppressive and lympholytic**. They cause a decrease in the peripheral levels of: * **Eosinophils (Eosinopenia):** They sequester eosinophils in the spleen and bone marrow and induce apoptosis. * **Basophils (Basopenia):** Similar to eosinophils, their circulating numbers are reduced. * **Lymphocytes (Lymphocytopenia):** Glucocorticoids cause the redistribution of T and B cells from the blood into other lymphoid compartments (like the bone marrow and lymph nodes) and can induce apoptosis in certain lymphocyte subsets. * **Monocytes (Monocytopenia):** Circulating levels also decrease. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic:** Glucocorticoids "drop" the **B-E-L-M** (Basophils, Eosinophils, Lymphocytes, Monocytes) and "raise" the **Neutrophils**. * **Clinical Correlation:** A patient on long-term steroid therapy will often show a high Total Leukocyte Count (TLC) on a CBC, but this is usually a physiological effect (demargination) rather than an active infection. * **Eosinopenia** is a very sensitive marker for hypercortisolism (Cushing’s syndrome).

Q: The Ivy technique is a test used to measure which of the following?

Bleeding time. **Explanation:** The **Ivy technique** is the standardized clinical method used to measure **Bleeding Time (BT)**. Bleeding time is a functional test of **primary hemostasis**, which depends on two main factors: the integrity of the vascular wall and, most importantly, **platelet function** (both number and quality). 1. **Why Option B is correct:** In the Ivy method, a blood pressure cuff is inflated to 40 mmHg on the upper arm to maintain constant capillary pressure. A standardized incision is made on the volar aspect of the forearm, and the time taken for the bleeding to stop (via the formation of a temporary platelet plug) is recorded. The normal range is typically 2–9 minutes. 2. **Why Option A is incorrect:** **Clotting Time (CT)** measures secondary hemostasis (the coagulation cascade and fibrin formation). It is typically measured using the **Lee-White method** or Capillary Tube method. 3. **Why Options C & D are incorrect:** BT and CT assess different phases of the clotting process. While they are often ordered together, the Ivy technique is specific only to the assessment of platelet plug formation. **High-Yield Clinical Pearls for NEET-PG:** * **Duke’s Method:** An older, less standardized method for BT involving an earlobe prick. * **Prolonged BT:** Seen in **Thrombocytopenia** (low count), **Glanzmann Thrombasthenia** (defective aggregation), **Bernard-Soulier Syndrome** (defective adhesion), and **von Willebrand Disease** (vWD). * **Note:** In vWD, both BT and aPTT may be prolonged, but BT is the primary screening tool for platelet-related dysfunction. * **Aspirin:** Irreversibly inhibits COX-1, prolonging Bleeding Time for the life of the platelet (approx. 7–10 days).

Q: What is the primary reason for the buffering action of hemoglobin?

Imidazole group of histidine. **Explanation:** The buffering capacity of hemoglobin (Hb) is primarily attributed to the **imidazole group of the amino acid histidine**. **1. Why the correct answer is right:** Hemoglobin contains 38 histidine residues per molecule. The imidazole group of histidine has a **pKa of approximately 6.8**, which is very close to the physiological pH of blood (7.4). According to the Henderson-Hasselbalch principle, a buffer is most effective when its pKa is near the pH of the medium. This allows the imidazole group to reversibly bind or release hydrogen ions ($H^+$), effectively neutralizing metabolic acids. Furthermore, deoxygenated hemoglobin (Deoxy-Hb) is a better buffer than oxyhemoglobin because its pKa increases, making it more basic and allowing it to carry more $H^+$ ions (the **Haldane Effect**). **2. Why the incorrect options are wrong:** * **Heme & Porphyrin:** These are the prosthetic groups responsible for oxygen binding. While they are structural components of hemoglobin, they do not possess the ionizable side chains necessary for significant pH buffering. * **Histidine group of imidazole:** This is a play on words. Imidazole is a chemical functional group *within* the amino acid histidine, not the other way around. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Most important intracellular buffer:** Hemoglobin (due to its high concentration and histidine content). * **Most important extracellular/plasma buffer:** Bicarbonate ($HCO_3^-$) system. * **Isohydric Principle:** All buffer systems in a compartment (like blood) are in equilibrium with the same $[H^+]$; therefore, a change in one system affects all others. * **Bohr Effect:** Increased $H^+$ (acidity) decreases Hb's affinity for $O_2$, shifting the dissociation curve to the right.

Q: Tissue macrophages are derived from which cell lineage?

Monocyte. **Explanation:** **1. Why Monocyte is Correct:** Tissue macrophages are part of the **Mononuclear Phagocyte System** (formerly known as the Reticuloendothelial System). Monocytes are produced in the bone marrow and released into the peripheral blood, where they circulate for about 10–20 hours. Once they migrate into various tissues, they undergo morphological and functional changes to become **Tissue Macrophages**. These cells are larger, contain more lysosomes, and possess a high capacity for phagocytosis and antigen presentation. **2. Why Other Options are Incorrect:** * **Neutrophils (A):** These are "microphages." While they are professional phagocytes and the first responders to acute inflammation, they are short-lived (hours to days) and do not transform into permanent tissue macrophages. * **Eosinophils (B):** These are specialized granulocytes primarily involved in allergic reactions and defense against helminthic (parasitic) infections. They do not differentiate into macrophages. * **All of the above (D):** This is incorrect because the lineage is specific to the monocyte-macrophage cell line. **3. High-Yield Clinical Pearls for NEET-PG:** * **Specific Tissue Macrophages (Must-know for exams):** * Liver: **Kupffer cells** * CNS: **Microglia** * Lungs: **Alveolar macrophages** (Dust cells) * Skin: **Langerhans cells** * Bone: **Osteoclasts** * Kidney: **Mesangial cells** * Placenta: **Hofbauer cells** * **Function:** Macrophages act as a bridge between innate and adaptive immunity by acting as **Antigen Presenting Cells (APCs)** via MHC II molecules. * **Cytokines:** They are the primary source of **IL-1, IL-6, and TNF-alpha**.

Q: What is the serum fibrinogen threshold considered adequate to promote coagulation?

150 mg%. **Explanation:** **Fibrinogen (Factor I)** is a high-molecular-weight plasma protein synthesized in the liver. It is the precursor to fibrin, which forms the structural meshwork of a blood clot. In a healthy individual, normal plasma fibrinogen levels range between **200–400 mg/dL**. 1. **Why 150 mg% is correct:** While the body can technically initiate clotting at lower levels, **150 mg/dL** is clinically recognized as the critical threshold required to maintain adequate hemostasis during physiological stress or surgery. Below this level, the strength and stability of the fibrin clot are significantly compromised, leading to an increased risk of bleeding. In clinical guidelines (such as those for Postpartum Hemorrhage or Trauma-Induced Coagulopathy), 150 mg/dL is often the trigger point for replacement therapy. 2. **Analysis of Incorrect Options:** * **100 mg%:** This is the threshold for "hypofibrinogenemia." While clotting can occur, it is often insufficient for surgical hemostasis. * **200 mg% & 250 mg%:** These values fall within the **normal physiological range**. While they are "adequate," they do not represent the minimum threshold or the critical "cut-off" point usually tested in exams regarding the promotion of coagulation in deficiency states. **High-Yield Clinical Pearls for NEET-PG:** * **Acute Phase Reactant:** Fibrinogen levels rise during inflammation, pregnancy, and stress. * **ESR Correlation:** Fibrinogen is the most important plasma protein contributing to the **Erythrocyte Sedimentation Rate (ESR)** by neutralizing the negative charge on RBCs (zeta potential), promoting rouleaux formation. * **Cryoprecipitate:** This is the blood product of choice for fibrinogen replacement, as it contains high concentrations of Factor I, VIII, XIII, and vWF. * **Afibrinogenemia:** A rare congenital condition where fibrinogen is undetectable, leading to severe bleeding diathesis.

Q: The vitamin K-dependent proteins C and S inactivate which factors?

Factor 8a and 5a. **Explanation:** The correct answer is **Factor 8a and 5a**. **Mechanism of Action:** Proteins C and S are natural anticoagulants synthesized in the liver in a Vitamin K-dependent manner. The process begins when **Thrombin** binds to **Thrombomodulin** on the endothelial surface. This complex activates Protein C into **Activated Protein C (APC)**. APC, using **Protein S as a cofactor**, proteolytically inactivates the active forms of the cofactors **Factor Va** and **Factor VIIIa**. By degrading these factors, the Protein C system inhibits the "prothrombinase complex" and the "tenase complex," effectively slowing down the coagulation cascade and preventing excessive clot formation. **Analysis of Incorrect Options:** * **Option B (7a and 5b):** Factor VIIa is inhibited by Tissue Factor Pathway Inhibitor (TFPI), not Protein C. "Factor 5b" is not a standard physiological term in the coagulation cascade. * **Option C (3a and 3b):** Factor III is Tissue Factor. It is not a target for Protein C/S inactivation. * **Option D:** Incorrect, as the action is specific to the cofactors of the common and intrinsic pathways (Va and VIIIa). **High-Yield Clinical Pearls for NEET-PG:** * **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 Activated Protein C. * **Warfarin-Induced Skin Necrosis:** Occurs in patients with underlying Protein C deficiency. Since Protein C has a shorter half-life than procoagulant factors (II, VII, IX, X), starting Warfarin creates a transient hypercoagulable state, leading to microvascular thrombosis. * **Vitamin K-dependent factors:** Procoagulants (II, VII, IX, X) and Anticoagulants (Protein C, S, and Z).

Q: What is the effect of G-CSF and GM-CSF on hematopoiesis?

Leukocytosis. **Explanation:** **G-CSF (Granulocyte Colony-Stimulating Factor)** and **GM-CSF (Granulocyte-Macrophage Colony-Stimulating Factor)** are potent hematopoietic growth factors that regulate the proliferation and differentiation of myeloid progenitor cells. 1. **Why Leukocytosis is Correct:** * **G-CSF** specifically stimulates the production and release of **neutrophils** from the bone marrow. * **GM-CSF** has a broader spectrum, stimulating the production of **neutrophils, monocytes, and eosinophils**. * The administration or endogenous surge of these factors leads to an increase in the total white blood cell (WBC) count, a condition known as **Leukocytosis**. 2. **Why Other Options are Incorrect:** * **Erythrocytosis:** This is primarily regulated by **Erythropoietin (EPO)**, which acts on erythroid precursors. G-CSF/GM-CSF do not significantly impact red cell mass. * **Leukopenia:** This refers to a decrease in WBCs. G-CSF and GM-CSF are actually used clinically to *reverse* leukopenia (specifically neutropenia). * **Thrombocytosis:** Platelet production is primarily regulated by **Thrombopoietin (TPO)**. While some cytokines have cross-reactivity, G-CSF is not a primary driver of platelet elevation. **Clinical Pearls for NEET-PG:** * **Filgrastim:** A recombinant G-CSF used to treat chemotherapy-induced neutropenia. * **Sargramostim:** A recombinant GM-CSF used in bone marrow transplantation. * **Side Effect:** The most common side effect of G-CSF therapy is **bone pain**, due to the rapid expansion of cells within the marrow cavity. * **Stem Cell Harvest:** G-CSF is used to "mobilize" hematopoietic stem cells (CD34+) from the bone marrow into the peripheral blood for collection.

Q: Where does erythropoiesis primarily occur during early gestation?

Yolk sac. **Explanation:** The site of erythropoiesis (red blood cell production) changes dynamically throughout intrauterine life to meet the oxygen demands of the developing embryo. **1. Why Yolk Sac is Correct:** During the **Mesoblastic stage** (early gestation), erythropoiesis begins around the 3rd week of development. It occurs in the **mesoderm of the yolk sac**, specifically within "blood islands." This process continues until approximately the 2nd to 3rd month of gestation, after which the liver takes over as the primary site (Hepatic stage). **2. Why Incorrect Options are Wrong:** * **Placenta:** While the placenta is the organ of nutrient and gas exchange between mother and fetus, it does not serve as a primary hematopoietic organ. * **Amniotic sac:** This is the fluid-filled sac surrounding the fetus; it provides protection and allows for movement but has no role in blood cell formation. * **Chorion:** The chorion is the outermost fetal membrane contributing to the placenta. While it contains early blood vessels, the primary site of initial hematopoiesis is specifically the yolk sac. **High-Yield Clinical Pearls for NEET-PG:** * **Timeline of Erythropoiesis:** * **0–2 months:** Yolk sac (Mesoblastic stage). * **2–7 months:** Liver (Primary) and Spleen (Hepatic stage). * **5–9 months:** Bone Marrow (Myeloid stage). * **Fetal Hemoglobin (HbF):** The primary hemoglobin produced during the hepatic stage is HbF ($\alpha_2\gamma_2$), which has a higher affinity for oxygen than adult hemoglobin (HbA). * **Post-natal:** In adults, the bone marrow of membranous bones (vertebrae, sternum, ribs, ilia) is the primary site. If bone marrow fails, **extramedullary hematopoiesis** can occur in the liver and spleen.

Question 1

Plasma cells are derived from which of the following cell types?

Accepted Answer

B lymphocytes

Answer

T lymphocytes

Answer

NK cells

Answer

Monocytes

Question 2

Glucocorticoids lead to an increase in blood levels of which of the following?

Accepted Answer

Neutrophils

Answer

Eosinophils

Answer

Basophils

Answer

Lymphocytes

Question 3

The Ivy technique is a test used to measure which of the following?

Accepted Answer

Bleeding time

Answer

Clotting time

Answer

Both clotting time and bleeding time

Answer

Neither clotting time nor bleeding time

Question 4

What is the primary reason for the buffering action of hemoglobin?

Accepted Answer

Imidazole group of histidine

Answer

Heme

Answer

Porphyrin

Answer

Histidine group of imidazole

Question 5

Tissue macrophages are derived from which cell lineage?

Accepted Answer

Monocyte

Answer

Neutrophil

Answer

Eosinophil

Answer

All of the above

Question 6

What is the serum fibrinogen threshold considered adequate to promote coagulation?

Accepted Answer

150 mg%

Answer

100 mg%

Answer

200 mg%

Answer

250 mg%

Question 7

The vitamin K-dependent proteins C and S inactivate which factors?

Accepted Answer

Factor 8a and 5a

Answer

Factor 7a and 5b

Answer

Factor 3a and 3b

Answer

All of the above

Question 8

A 25-year-old female patient with a hemoglobin level of 4 gm/dL was given a blood transfusion with blood stored for 10 days. Which of the following statements is FALSE?

Accepted Answer

The fall in 2,3-DPG level is less when blood is stored in acid-citrate-dextrose solution.

Answer

The oxygen-carrying capacity of this blood is reduced.

Answer

The 2,3-diphosphoglycerate (2,3-DPG) level falls in stored blood.

Answer

An increase in 2,3-DPG levels causes a rightward shift of the oxygen-hemoglobin dissociation curve.

Question 9

What is the effect of G-CSF and GM-CSF on hematopoiesis?

Accepted Answer

Leukocytosis

Answer

Erythrocytosis

Answer

Leukopenia

Answer

Thrombocytosis

Question 10

Where does erythropoiesis primarily occur during early gestation?

Accepted Answer

Yolk sac

Answer

Placenta

Answer

Amniotic sac

Answer

Chorion

Blood and Immunity — MCQs

Blood and Immunity — MCQs

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