Blood and Immunity Practice Questions

Q: In fetal life, in which of the following sites are red blood cells NOT produced?

Lymph node. **Explanation:** The production of red blood cells (erythropoiesis) in fetal life occurs in distinct stages, moving through different anatomical sites as the fetus develops. This process is categorized into three stages: 1. **Mesoblastic Stage (Weeks 3–8):** Erythropoiesis begins in the **yolk sac** (specifically the blood islands). 2. **Hepatic Stage (Month 2 – Birth):** The **liver** becomes the primary site of RBC production, peaking at the 5th month. The **spleen** also contributes significantly during the 3rd to 6th months. 3. **Myeloid Stage (Month 5 – Life):** The **bone marrow** begins production around the 20th week and becomes the dominant site by the 7th month and throughout postnatal life. **Why Lymph Nodes are the Correct Answer:** While lymph nodes are part of the hematopoietic system, they are primarily involved in **lymphopoiesis** (production of lymphocytes) and immune filtration. They do not serve as a site for erythropoiesis during normal fetal development. **Analysis of Incorrect Options:** * **A. Liver:** The main site of erythropoiesis during the second trimester. * **C. Spleen:** Acts as a secondary lymphoid and hematopoietic organ during the middle trimester. * **D. Bone Marrow:** Becomes the definitive site for all blood cell lines in the late third trimester and remains so after birth. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Erythropoiesis Sites:** **"Young Liver Synthesizes Blood"** (Yolk sac → Liver → Spleen → Bone marrow). * **Extramedullary Hematopoiesis:** In certain pathological states (e.g., Thalassemia, Myelofibrosis), the liver and spleen can resume RBC production in adults. * **Hemoglobin Transition:** Fetal hemoglobin (HbF: $\alpha_2\gamma_2$) is the predominant type during the hepatic stage, transitioning to Adult hemoglobin (HbA: $\alpha_2\beta_2$) as bone marrow production takes over.

Q: What is the first cell in the development of red blood cells?

Proerythroblast. **Explanation:** The process of red blood cell formation, known as **erythropoiesis**, occurs in the bone marrow. It begins with a multipotent hematopoietic stem cell, which differentiates into a **Proerythroblast** (also called a Pronormoblast). **Why Proerythroblast is correct:** The Proerythroblast is the **first morphologically identifiable committed precursor** of the erythroid series. It is a large cell with a big nucleus, visible nucleoli, and a thin rim of basophilic cytoplasm. Once a stem cell differentiates into a proerythroblast, it is "committed" to becoming a mature erythrocyte. **Analysis of Incorrect Options:** * **Basophilic erythroblast (Early Normoblast):** This is the second stage. It is smaller than the proerythroblast and shows intense cytoplasmic basophilia due to an accumulation of RNA for hemoglobin synthesis. * **Intermediate normoblast (Polychromatophilic erythroblast):** This is the third stage. It is characterized by a "checkered" nucleus and a cytoplasm that appears grayish/purple because it contains both basic RNA and acidic hemoglobin. * **Reticulocyte:** This is the penultimate stage, occurring after the nucleus is extruded (at the orthochromatic stage). It is an immature RBC that stays in the marrow for 1–2 days before entering the peripheral circulation. **NEET-PG High-Yield Pearls:** 1. **Hemoglobin synthesis** begins in the **Proerythroblast** stage, but becomes visible (morphologically detectable) in the **Intermediate Normoblast** stage. 2. The **nucleus is extruded** at the **Orthochromatic Normoblast** (Late Normoblast) stage. 3. **Reticulocyte count** is the best clinical indicator of effective erythropoiesis in the bone marrow. 4. **Erythropoietin (EPO)** primarily acts on the CFU-E (Colony Forming Unit-Erythroid) to stimulate the production of proerythroblasts.

Q: What is the primary site of red blood cell formation in a healthy 20-year-old male?

Flat bones. ### Explanation **1. Why "Flat bones" is correct:** In a healthy adult (post-puberty), the active red bone marrow (hematopoietic marrow) is restricted to the **axial skeleton** and specific flat bones. These include the vertebrae, sternum, ribs, pelvis (iliac crest), and the skull. By age 20, the peripheral marrow in long bones has largely been replaced by inactive yellow marrow (fat). Therefore, the flat bones and the proximal ends of the humerus and femur are the primary sites of erythropoiesis. **2. Why the other options are incorrect:** * **Long bones:** While the shafts of long bones (e.g., tibia, fibula) are active sites of RBC production in children, they undergo "marrow recession" and are replaced by yellow marrow by age 20. * **Liver:** This is the primary site of erythropoiesis during the **second trimester** (hepatic stage) of fetal development. In adults, the liver only produces RBCs in pathological states (extramedullary hematopoiesis). * **Yolk sac:** This is the **first** site of erythropoiesis, occurring during the first few weeks of embryonic life (mesoblastic stage). **3. High-Yield NEET-PG Pearls:** * **Timeline of Erythropoiesis:** * *0–2 months:* Yolk sac * *2–7 months:* Liver (and spleen) * *5–9 months:* Bone marrow (becomes the dominant site by birth) * **Clinical Site for Biopsy:** In adults, the **posterior superior iliac spine (pelvis)** is the preferred site for bone marrow aspiration/biopsy because it is a flat bone that remains hematopoietically active throughout life. * **Extramedullary Hematopoiesis:** If the bone marrow fails (e.g., Myelofibrosis), the liver and spleen may resume RBC production, often leading to hepatosplenomegaly.

Q: What is true about the Rh factor?

There are no natural anti-Rh antibodies in serum.. ### Explanation **1. Why Option A is Correct:** Unlike the ABO system, where antibodies (isoagglutinins) develop spontaneously within the first few months of life, the Rh system has **no naturally occurring antibodies**. Anti-D antibodies are only produced after an Rh-negative individual is "sensitized"—either through a mismatched blood transfusion or during pregnancy with an Rh-positive fetus. This is a crucial distinction in transfusion medicine. **2. Analysis of Incorrect Options:** * **Option B:** The Rh factor is an inherited protein found on the surface of red blood cells. It is autosomal dominant and not sex-linked; therefore, it occurs in both males and females. * **Option C:** In the Indian population, approximately **93–95%** of individuals are Rh-positive. Only about 5–7% are Rh-negative. (In Caucasians, the Rh-negative prevalence is higher, around 15%). * **Option D:** The Rh system consists of several antigens (C, D, E, c, d, e). The **D antigen is the most potent** and highly immunogenic. Its presence or absence determines whether a person is classified as Rh-positive or Rh-negative. **3. Clinical Pearls for NEET-PG:** * **Erythroblastosis Fetalis:** Occurs when an Rh-negative mother carries an Rh-positive fetus. Sensitization usually happens during the first delivery, affecting subsequent pregnancies. * **Prophylaxis:** To prevent sensitization, **Anti-D (RhoGAM)** is administered to Rh-negative mothers at 28 weeks of gestation and within 72 hours of delivering an Rh-positive baby. * **Landsteiner & Wiener:** They discovered the Rh factor in 1940 using the blood of Rhesus monkeys. * **Fisher-Race Nomenclature:** Postulates that Rh antigens are determined by three pairs of closely linked genes (C/c, D/d, E/e).

Q: Which cell does not differentiate in the bone marrow?

T lymphocyte. ### Explanation The correct answer is **B. T lymphocyte**. **1. Why T lymphocytes are the correct answer:** All blood cells originate from **Pluripotent Hematopoietic Stem Cells (PHSCs)** in the bone marrow. However, while T lymphocytes are *produced* in the bone marrow, they do not *differentiate* or mature there. Instead, pro-T cells migrate via the bloodstream to the **Thymus**. In the thymus, they undergo "thymic education," where they differentiate into mature T cells (CD4+ or CD8+), develop self-tolerance, and acquire their T-cell receptors (TCR). **2. Why the other options are incorrect:** * **A. B lymphocyte:** Unlike T cells, B lymphocytes undergo both production and maturation/differentiation within the **Bone marrow** (hence the name "B" cell). They only leave for secondary lymphoid organs once they are mature. * **C & D. Neutrophils and Basophils:** These are granulocytes belonging to the myeloid lineage. Their entire process of myelopoiesis—from myeloblasts to mature segmented cells—occurs completely within the bone marrow before they are released into the peripheral circulation. **3. High-Yield Clinical Pearls for NEET-PG:** * **Primary Lymphoid Organs:** Bone marrow and Thymus (where lymphocytes are formed/matured). * **Secondary Lymphoid Organs:** Lymph nodes, Spleen, Peyer’s patches, and Tonsils (where immune responses occur). * **Thymic Involution:** The thymus is most active during childhood and begins to atrophy (replaced by fat) after puberty, though T-cell production continues at a lower rate. * **DiGeorge Syndrome:** A classic clinical correlation where the failure of the 3rd and 4th pharyngeal pouches to develop leads to thymic aplasia and a profound deficiency in mature T cells.

Q: What is the lifespan of fetal red blood cells?

Two-thirds of adult red blood cells. **Explanation:** The correct answer is **D (Two-thirds of adult red blood cells)**. **1. Underlying Medical Concept:** The lifespan of a normal adult red blood cell (RBC) is approximately **120 days**. In contrast, fetal RBCs have a significantly shorter lifespan of approximately **80 to 90 days**. Mathematically, 80 days is roughly two-thirds of 120 days. This shorter survival is attributed to several physiological factors: * **Metabolic differences:** Fetal RBCs have lower levels of certain enzymes (like phosphofructokinase) and lower ATP concentrations. * **Oxidative stress:** They are more prone to oxidative damage. * **Membrane characteristics:** Fetal RBC membranes are less deformable, making them more susceptible to sequestration and destruction in the splenic circulation. **2. Analysis of Incorrect Options:** * **Option A (Same as adult):** Incorrect. Fetal RBCs are more fragile and metabolically distinct, leading to faster turnover. * **Option B (One-fourth):** Incorrect. This would imply a lifespan of only 30 days, which is seen in severe pathological states (like certain hemolytic anemias), not normal fetal physiology. * **Option C (One-half):** Incorrect. While 60 days is short, it underestimates the actual 80-90 day survival of full-term fetal RBCs. **3. NEET-PG High-Yield Pearls:** * **Neonatal Jaundice:** The shorter lifespan of fetal RBCs, combined with a higher total RBC mass (polycythemia) and an immature liver (low glucuronyl transferase activity), is the primary cause of **physiological jaundice** in newborns. * **Hemoglobin Shift:** Fetal hemoglobin (HbF: $\alpha_2\gamma_2$) has a higher affinity for oxygen than adult hemoglobin (HbA: $\alpha_2\beta_2$) because it binds poorly to 2,3-BPG. * **Preterm Infants:** The RBC lifespan is even shorter in premature neonates, often ranging from **35 to 50 days**.

Question 1

All of the following are functions of the spleen EXCEPT?

Accepted Answer

Initiation of adaptive immune response from filtration of lymph.

Answer

Clearance of damaged or aged red blood cells (RBCs) from the blood.

Answer

Extramedullary site for hematopoiesis and recycling iron.

Answer

Clearance of encapsulated bacteria from the bloodstream.

Question 2

In fetal life, in which of the following sites are red blood cells NOT produced?

Accepted Answer

Lymph node

Answer

Liver

Answer

Spleen

Answer

Bone marrow

Question 3

What is the first cell in the development of red blood cells?

Accepted Answer

Proerythroblast

Answer

Intermediate normoblast

Answer

Reticulocyte

Answer

Basophilic erythroblast

Question 4

Which of the following does NOT occur during hemostasis?

Accepted Answer

None of the above

Answer

Vasospasm of the blood vessel

Answer

Platelet plug formation

Answer

Dissolution of the clot by plasmin

Question 5

What is the primary site of red blood cell formation in a healthy 20-year-old male?

Accepted Answer

Flat bones

Answer

Long bones

Answer

Liver

Answer

Yolk sac

Question 6

Which of the following promotes rouleaux formation?

Accepted Answer

Fibrinogen

Answer

Zeta potential on RBC membrane

Answer

Albumin

Answer

Biconcave shape of RBC

Question 7

What is true about the Rh factor?

Accepted Answer

There are no natural anti-Rh antibodies in serum.

Answer

It is seen only in females.

Answer

Approximately 15% of Indians are Rh positive.

Answer

The D antigen is the least potent Rh antigen.

Question 8

Which cell does not differentiate in the bone marrow?

Accepted Answer

T lymphocyte

Answer

B lymphocyte

Answer

Neutrophil

Answer

Basophil

Question 9

Which of the following blood transfusions will most likely result in a transfusion reaction, assuming the patient has never received a transfusion before?

Accepted Answer

Type A Rh-positive packed cells to an O Rh-positive patient

Answer

Type O Rh-negative packed cells to an AB Rh-positive patient

Answer

Type A Rh-positive packed cells to an A Rh-negative patient

Answer

Type AB Rh-positive packed cells to an AB Rh-positive patient

Question 10

What is the lifespan of fetal red blood cells?

Accepted Answer

Two-thirds of adult red blood cells

Answer

Same as adult red blood cells

Answer

One-fourth of adult red blood cells

Answer

One-half of adult red blood cells

Blood and Immunity — MCQs

Blood and Immunity — MCQs

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