Blood and Immunity Practice Questions

Q: The maximum life of a transfused R.B.C. is -

50 days. ***50 days*** - The **practical maximum lifespan** of a **transfused red blood cell (RBC)** is approximately **50-60 days** in the recipient's circulation, representing the T50 (median survival time) for stored blood. - This is shorter than the natural lifespan of native RBCs (around 120 days) due to **storage lesions** - damage occurring during blood bank storage including ATP depletion, membrane changes, and reduced deformability. - While some transfused RBCs may survive longer, the majority do not exceed 50-60 days due to cumulative storage-related damage. *One day* - A lifespan of one day is far too short for transfused **RBCs**, which are expected to circulate for weeks to provide oxygen-carrying capacity. - This short duration would indicate immediate destruction or incompatibility, which is not the goal of a successful transfusion. *15 days* - While 15 days is longer than one day, it is still a significant underestimation of the **typical survival** of successfully transfused RBCs. - This duration would suggest suboptimal survival, though some stored RBCs might be cleared within this timeframe due to severe storage lesions. *One hour* - A lifespan of one hour for transfused **RBCs** is indicative of a severe **transfusion reaction** leading to rapid hemolysis. - This scenario represents a failed transfusion with acute destruction of donor cells, which is not the maximum life expectancy.

Q: Cortisol increases all of the following components except:

Eosinophils. ***Eosinophils*** - Cortisol causes **eosinopenia** (a decrease in eosinophils) by increasing their sequestration in tissues and promoting their apoptosis. - This effect is a classic indicator of stress and can be observed in conditions of elevated endogenous or exogenous cortisol. *Monocytes* - Cortisol typically causes a **mild monocytosis** (increase in circulating monocytes), although this effect can vary. - It impacts the trafficking and differentiation of monocytes, leading to their transient increase in the bloodstream. *RBCs* - Cortisol can lead to a slight **increase in red blood cell (RBC) count** or hemoglobin concentration. - This effect is partly due to hemoconcentration and partly by promoting erythropoiesis. *Platelets* - Cortisol generally causes a **thrombocytosis** (increase in platelet count). - This effect is thought to be mediated by various factors, including cytokine interactions and direct effects on megakaryopoiesis.

Q: Which of the following is an inhibitor of platelet aggregation?

Prostacyclin. ***Prostacyclin*** - **Prostacyclin (PGI2)** is a potent **vasodilator** and **inhibitor of platelet aggregation**, primarily produced by endothelial cells. - It counters the pro-aggregatory effects of **thromboxane A2**, maintaining blood vessel patency. *Thromboxane A2* - **Thromboxane A2 (TXA2)** is a potent **inducer of platelet aggregation** and a **vasoconstrictor**. - It is synthesized by activated platelets and promotes thrombus formation. *Leukotriene A4* - **Leukotriene A4 (LTA4)** is an intermediate in the synthesis of other **leukotrienes** (LTC4, LTD4, LTE4), which are involved in inflammation and bronchoconstriction. - It is not directly involved in the inhibition or activation of platelet aggregation. *Prostaglandin H2* - **Prostaglandin H2 (PGH2)** is an unstable intermediate in the synthesis of both **prostacyclin** and **thromboxane A2**. - Its effects are primarily dependent on the downstream enzymes present in specific cells (e.g., endothelial cells versus platelets).

Q: ABO antigens are not found in:

CSF. ***CSF*** - ABO antigens are typically expressed on the surface of **red blood cells** and in the secretions of individuals classified as **secretors**. - **Cerebrospinal fluid (CSF)** is generally devoid of these antigens. *Semen* - ABO antigens can be found in **semen**, particularly in individuals who are secretors. - This is due to the presence of **secreted bodily fluids** containing soluble forms of these antigens. *Saliva* - **Saliva** is a well-known source of soluble ABO antigens in secretor individuals. - The presence of these antigens in saliva is often used in **forensic testing** and blood group determination. *Tears* - Similar to other bodily secretions, **tears** can contain soluble ABO antigens in secretor individuals. - This is part of the general secretion of these antigens into exocrine fluids.

Q: Basophils are activated by:

Cell-bound IgE. ***Cell-bound IgE*** - Basophils express **Fc receptors** for **IgE** on their cell surface. - When **allergens** bind to IgE antibodies already attached to these receptors, it triggers **basophil activation** and degranulation, releasing inflammatory mediators. *Neutrophils* - **Neutrophils** are phagocytic cells primarily involved in the anti-bacterial immune response and do not directly activate basophils. - They are distinct leukocyte populations with different roles in immunity. *Killer inhibitory peptide* - **Killer inhibitory peptides** (KIRs) are receptors found on **Natural Killer (NK) cells** that inhibit their cytotoxic activity when bound to MHC class I molecules. - They are not involved in the activation of basophils. *IL-5* - **Interleukin-5 (IL-5)** is a cytokine primarily involved in the **growth**, differentiation, and activation of **eosinophils**. - While basophils can be influenced by various cytokines, IL-5 is not their primary activator.

Q: In a platelet poor plasma sample calcium and tissue thromboplastin are added. This is used to assess which of the following pathways?

Extrinsic. ***Extrinsic*** - The addition of **tissue thromboplastin** (containing tissue factor) and **calcium** to platelet-poor plasma directly activates the extrinsic pathway of coagulation. - This combination is used in the **prothrombin time (PT)** test, which specifically measures the integrity of the extrinsic and common pathways. *Common* - While the common pathway is utilized in this test, the direct activators of tissue thromboplastin and calcium specifically initiate the extrinsic pathway, which then feeds into the common pathway. - The PT test assesses the common pathway, but the initial trigger for the test setup outlined is the extrinsic arm. *Intrinsic* - The intrinsic pathway is initiated by factors present within the blood, such as contact with a negatively charged surface (e.g., glass), and is assessed by the **activated partial thromboplastin time (aPTT)**. - Tissue thromboplastin is not a component of the intrinsic pathway activation cascade. *Fibrinolytic* - The fibrinolytic pathway is responsible for the breakdown of clots and involves plasminogen activators and plasmin. - The addition of calcium and tissue thromboplastin is designed to initiate clot formation, not clot breakdown.

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

Endothelial cells. ***Endothelial cells*** - **Von Willebrand factor (vWF)** is primarily synthesized and secreted by **endothelial cells** lining blood vessels. - It is stored in **Weibel-Palade bodies** within endothelial cells and is released upon stimulation, playing a crucial role in **hemostasis**. *Platelets* - While **platelets** can bind to and carry vWF, they do not synthesize it. - Platelets have **vWF receptors** (e.g., glycoprotein Ib) that allow them to adhere to vWF at sites of vascular injury. *Fibroblast* - **Fibroblasts** are connective tissue cells that produce components of the extracellular matrix, such as collagen and elastin. - They are not involved in the synthesis or secretion of **vWF**. *Macrophages* - **Macrophages** are immune cells involved in phagocytosis and antigen presentation. - They do not produce **vWF**; their primary role is in immune surveillance and removal of cellular debris.

Q: In ABO blood grouping, which is False?

ABO antibodies are natural and present since birth. ***ABO antibodies are natural and present since birth*** - **ABO antibodies** are naturally occurring, but they are typically **not present at birth** [1]. - They develop within the **first 3 to 6 months of life** as a response to exposure to similar antigens in the environment (e.g., bacteria). *IgM is most common antibody in ABO* - The primary **ABO antibodies** (anti-A, anti-B) are indeed predominantly **IgM antibodies** [1]. - IgM antibodies are large pentameric structures, and their size prevents them from crossing the placenta [2]. *ABO are carbohydrate Ag* - The **ABO blood group antigens** (A, B, H) are **carbohydrate structures** (glycans) found on the surface of red blood cells and other tissues. - These carbohydrate chains are attached to proteins or lipids. *Ab are present only if Ag is absent* - This statement is a fundamental principle of ABO blood grouping: individuals naturally produce antibodies against the **ABO antigens** they **lack** [1]. - For example, a person with **Type A blood** (A antigen present) will have **anti-B antibodies** (B antigen absent). **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 627-628. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 469-470.

Q: Which factor is not involved in the intrinsic coagulation pathway?

Factor VII. ***Factor VII*** - **Factor VII** is a key component of the **extrinsic coagulation pathway**, which is initiated by **tissue factor** released upon vascular injury. - It forms a complex with tissue factor and calcium, which then activates Factor X to begin the common pathway. *Factor IX* - **Factor IX** is an integral part of the **intrinsic coagulation pathway**, activated by **Factor XIa** in the presence of calcium and phospholipids. - Once activated (Factor IXa), it forms a complex with **Factor VIIIa** to activate Factor X. *Factor X* - **Factor X** is a component of the **common coagulation pathway**, acting as the point where both the intrinsic and extrinsic pathways converge. - It is activated by both the intrinsic (Factor IXa/VIIIa complex) and extrinsic (Factor VIIa/tissue factor complex) pathways, forming **Factor Xa**. *Factor VIII* - **Factor VIII** is a crucial cofactor in the **intrinsic coagulation pathway**, where its activated form, **Factor VIIIa**, dramatically enhances the activity of Factor IXa. - It circulates bound to **von Willebrand factor** and is released and activated by thrombin.

Q: Erythropoietin is secreted by which of the following organs?

Kidney. ***Kidney*** - The **kidneys** are the primary site of erythropoietin production in adults, particularly the **peritubular interstitial cells**. - Erythropoietin's main function is to stimulate **red blood cell production** in the bone marrow in response to hypoxia. *Muscle* - Muscles are involved in movement and metabolism but do not produce **erythropoietin**. - They primarily store glycogen and generate force through contraction. *Liver* - The liver produces erythropoietin during **fetal development** but contributes minimally to its production in adulthood. - Its main functions include metabolism, detoxification, and protein synthesis. *Heart* - The heart is responsible for **pumping blood** throughout the body and does not produce **erythropoietin**. - It primarily consists of cardiac muscle tissue.

Question 1

The maximum life of a transfused R.B.C. is -

Accepted Answer

50 days

Answer

One day

Answer

15 days

Answer

One hour

Question 2

Cortisol increases all of the following components except:

Accepted Answer

Eosinophils

Answer

Monocytes

Answer

RBCs

Answer

Platelets

Question 3

Which of the following is an inhibitor of platelet aggregation?

Accepted Answer

Prostacyclin

Answer

Thromboxane A2

Answer

Leukotriene A4

Answer

Prostaglandin H2

Question 4

ABO antigens are not found in:

Accepted Answer

CSF

Answer

Semen

Answer

Saliva

Answer

Tears

Question 5

Basophils are activated by:

Accepted Answer

Cell-bound IgE

Answer

Neutrophils

Answer

Killer inhibitory peptide

Answer

IL-5

Question 6

In a platelet poor plasma sample calcium and tissue thromboplastin are added. This is used to assess which of the following pathways?

Accepted Answer

Extrinsic

Answer

Common

Answer

Intrinsic

Answer

Fibrinolytic

Question 7

Von Willebrand factor is secreted by which of the following?

Accepted Answer

Endothelial cells

Answer

Platelets

Answer

Fibroblasts

Answer

Macrophages

Question 8

In ABO blood grouping, which is False?

Accepted Answer

ABO antibodies are natural and present since birth

Answer

IgM is most common antibody in ABO

Answer

ABO are carbohydrate Ag

Answer

Ab are present only if Ag is absent

Question 9

Which factor is not involved in the intrinsic coagulation pathway?

Accepted Answer

Factor VII

Answer

Factor IX

Answer

Factor X

Answer

Factor VIII

Question 10

Erythropoietin is secreted by which of the following organs?

Accepted Answer

Kidney

Answer

Muscle

Answer

Liver

Answer

Heart

Blood and Immunity — MCQs

Blood and Immunity — MCQs

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