Blood and Immunity Practice Questions

Q: Which interleukin is needed for differentiation of eosinophils?

IL5. **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.

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

After 6 months of birth. **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.

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

Polycythemia. **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.

Q: Serotonin is secreted by which of the following?

Platelets. **Explanation:** **Correct Answer: C. Platelets** **Medical Concept:** Serotonin (5-hydroxytryptamine) is a potent vasoconstrictor and signaling molecule. While it is synthesized primarily in the enterochromaffin cells of the gastrointestinal tract, it is not synthesized by platelets. Instead, **platelets actively take up serotonin** from the plasma via the serotonin transporter (SERT) and store it in high concentrations within their **dense granules (delta granules)**. During platelet activation and the subsequent release reaction, serotonin is secreted into the local environment to promote vasoconstriction and enhance platelet aggregation, playing a crucial role in primary hemostasis. **Why other options are incorrect:** * **Leukocytes (WBCs):** While some leukocytes (like basophils) release histamine and heparin, they are not the primary storage or secretory sites for serotonin in the blood. * **RBCs:** Red blood cells are specialized for gas transport (Oxygen/CO2) and do not possess the machinery or granules to store or secrete serotonin. * **Vessel Wall:** The vascular endothelium produces substances like Nitric Oxide (NO) and Prostacyclin ($PGI_2$) for vasodilation, and Endothelin-1 for vasoconstriction, but it does not secrete serotonin. **High-Yield Clinical Pearls for NEET-PG:** * **Platelet Granules:** * **Dense (Delta) Granules:** Contain **SAC** (Serotonin, ADP/ATP, Calcium). * **Alpha Granules:** Contain vWF, Fibrinogen, Platelet Factor 4, and PDGF. * **Serotonin Function:** In the blood, it acts as a vasoconstrictor to limit blood loss; in the CNS, it acts as a neurotransmitter regulating mood and sleep. * **Carcinoid Syndrome:** A clinical condition where neuroendocrine tumors secrete excessive serotonin, leading to flushing, diarrhea, and right-sided heart failure.

Q: Hemagglutinin (Anti-A and Anti-B) are which type of antibodies?

IgM. **Explanation:** The correct answer is **B. IgM**. **Why IgM is correct:** Hemagglutinins (Anti-A and Anti-B) are naturally occurring antibodies found in the plasma of individuals who lack the corresponding antigens on their red blood cells. These are primarily **IgM** antibodies. Because IgM is a large pentameric molecule, it is highly efficient at agglutination (clumping) and activating the classical complement pathway. Crucially, due to their high molecular weight, IgM antibodies **cannot cross the placenta**, which is why ABO incompatibility between mother and fetus rarely causes severe Hemolytic Disease of the Newborn (HDN) in the same way Rh incompatibility does. **Why the other options are incorrect:** * **IgG:** While some "immune-type" Anti-A or Anti-B (seen after sensitization) can be IgG, the standard naturally occurring hemagglutinins are IgM. IgG is the only antibody that crosses the placenta. * **IgA:** These are primarily found in secretions (tears, saliva, colostrum) and provide mucosal immunity. They are not the primary antibodies responsible for ABO blood group reactions. * **IgE:** These antibodies are involved in Type I hypersensitivity reactions (allergies) and defense against parasitic infections. **High-Yield Clinical Pearls for NEET-PG:** * **Cold Agglutinins:** Naturally occurring ABO antibodies are "cold antibodies," meaning they react best at temperatures below 37°C (usually 4°C). * **Landsteiner’s Law:** States that if an agglutinogen (antigen) is present on RBCs, the corresponding agglutinin (antibody) must be absent from the plasma. * **Universal Donor/Recipient:** Type O individuals are universal donors (no A/B antigens); Type AB individuals are universal recipients (no Anti-A/Anti-B antibodies). * **Development:** Anti-A and Anti-B antibodies are not present at birth; they develop within 3–6 months of life due to exposure to similar antigens in gut bacteria and food.

Q: Which of the following is not useful for coagulation?

Plasmin. **Explanation:** The core concept tested here is the distinction between **coagulation (clot formation)** and **fibrinolysis (clot dissolution)**. **Why Plasmin is the correct answer:** Plasmin is a proteolytic enzyme whose primary function is **fibrinolysis**. It is the active form of plasminogen, activated by Tissue Plasminogen Activator (tPA). Plasmin works by degrading fibrin mesh into Fibrin Degradation Products (FDPs) and D-dimers. Therefore, it does not assist in coagulation; rather, it acts to dissolve an existing clot to prevent vessel occlusion. **Why the other options are incorrect:** * **Thrombin (Factor IIa):** This is the most critical enzyme in the coagulation cascade. It converts soluble fibrinogen into insoluble fibrin monomers and activates Factors V, VIII, XI, and XIII. * **Calcium (Factor IV):** Calcium ions are essential cofactors for almost all steps of the coagulation pathway (except the initial stages of the intrinsic pathway). Without calcium, blood cannot clot, which is why chelating agents like EDTA or Citrate are used in blood vials to prevent clotting. * **Fibrin (Factor Ia):** Fibrin is the end-product of the coagulation cascade. It forms the physical "mesh" or polymer that traps platelets and blood cells to create a stable hemostatic plug. **High-Yield NEET-PG Pearls:** * **D-Dimer:** A specific degradation product of cross-linked fibrin, used clinically to rule out DVT and PE. * **Antidote for Plasmin overactivity:** Tranexamic acid (TXA) or Epsilon-aminocaproic acid (EACA) inhibits plasminogen activation. * **Vitamin K-dependent factors:** II, VII, IX, and X (Calcium is required for these factors to bind to phospholipid surfaces).

Question 1

Which of the following is a feature of a reticulocyte?

Accepted Answer

No nucleus

Answer

Constitute 10% of the red cells

Answer

Smaller in size than RBCs

Answer

Mature in lymph nodes

Question 2

Which of the following is NOT related to fetal erythropoiesis?

Accepted Answer

In the embryonic phase, erythropoiesis is first demonstrated in the yolk sac.

Answer

By the 20th week of gestation, the liver becomes the major site of erythropoiesis.

Answer

Near term, the bone marrow becomes the major site of erythropoiesis.

Answer

At term, 75-80% of hemoglobin is the fetal type (HbF).

Question 3

Which interleukin is needed for differentiation of eosinophils?

Accepted Answer

IL5

Answer

IL1

Answer

IL2

Answer

IL4

Question 4

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

Accepted Answer

Multiple myeloma

Answer

Fasting state

Answer

Hypoglycemia

Answer

Amyloidogenesis

Question 5

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?

Accepted Answer

Bombay blood group

Answer

A positive

Answer

O positive

Answer

B negative

Question 6

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

Accepted Answer

After 6 months of birth

Answer

Just after birth

Answer

1 week after birth

Answer

6 weeks after birth

Question 7

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

Accepted Answer

Polycythemia

Answer

Von Willebrand's disease

Answer

Christmas disease

Answer

Haemophilia

Question 8

Serotonin is secreted by which of the following?

Accepted Answer

Platelets

Answer

Leukocytes

Answer

RBCs

Answer

Vessel wall

Question 9

Hemagglutinin (Anti-A and Anti-B) are which type of antibodies?

Accepted Answer

IgM

Answer

IgG

Answer

IgA

Answer

IgE

Question 10

Which of the following is not useful for coagulation?

Accepted Answer

Plasmin

Answer

Thrombin

Answer

Calcium

Answer

Fibrin

Blood and Immunity — MCQs

Blood and Immunity — MCQs

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