Blood and Immunity Practice Questions

Q: Which of the following mechanisms facilitates the delivery of oxygen in fetal circulation?

Higher affinity of HbF for O2. ***Higher affinity of HbF for O2*** - Fetal hemoglobin (**HbF**) has a **higher affinity for oxygen** than adult hemoglobin (**HbA**), due to its reduced binding to **2,3-bisphosphoglycerate (2,3-BPG)**. - This increased affinity allows HbF to extract oxygen more efficiently from the maternal blood at the **placenta**, facilitating oxygen transfer to the fetus. *Bohr's effect* - The Bohr effect describes how a decrease in pH (more acidic) or an increase in CO2 or temperature **reduces hemoglobin's affinity for oxygen**, promoting oxygen release to tissues. - While important for oxygen delivery in maternal tissues, it would hinder oxygen uptake by fetal blood at the placenta if it were the primary mechanism. *Halden's effect* - The Haldane effect states that the deoxygenation of blood increases its ability to carry carbon dioxide, and conversely, the oxygenation of blood **decreases its ability to carry carbon dioxide**. - This effect primarily concerns **CO2 transport** in the blood and does not directly facilitate oxygen delivery to fetal tissues. *None of the options* - This option is incorrect because the **higher affinity of HbF for oxygen** is a well-established and crucial mechanism for oxygen delivery in fetal circulation.

Q: Where is the primary site of synthesis for Complement component C1 inhibitor (C1-INH)?

Liver. ***Liver*** - The **liver** is the principal site of synthesis for most plasma proteins, including the **complement components** and their inhibitors such as C1-INH. - **Hepatocytes** within the liver are responsible for the constant production and secretion of C1-INH into the bloodstream. *Macrophages* - While **macrophages** can produce certain complement components and cytokines, they are not the primary site for the systemic synthesis of **C1-INH**. - Macrophage-derived complement proteins often play a more localized role in immune responses. *Intestinal epithelium* - The **intestinal epithelium** is primarily involved in digestion, nutrient absorption, and acting as a barrier, not in the bulk synthesis of systemic complement inhibitors like **C1-INH**. - These cells do produce some immune-related molecules, but not C1-INH. *Endothelium* - **Endothelial cells** lining blood vessels play roles in regulating vascular tone and local inflammation, but they are not the main producers of circulating **C1-INH**. - They can express and modify certain adhesion molecules and cytokines, but large-scale protein synthesis like C1-INH occurs elsewhere.

Q: Gamma globulins are synthesized in?

Plasma cells. ***Plasma cells*** - **Plasma cells** are differentiated B lymphocytes that are specialized in producing and secreting large quantities of **antibodies (gamma globulins)**. - This process is a crucial part of the body's **humoral immune response** to pathogens. *Liver* - The **liver** is primarily responsible for synthesizing most other plasma proteins, such as **albumin**, **clotting factors**, and lipoproteins. - While important for protein metabolism, it does not directly synthesize **gamma globulins**. *Spleen* - The **spleen** is a secondary lymphoid organ involved in filtering blood, storing blood cells, and initiating immune responses. - It contains immune cells like B cells and plasma cells, but it is not the primary site of **gamma globulin synthesis** itself. *Kidney* - The **kidney's** main functions are filtering waste products from the blood, regulating blood pressure, and producing hormones. - It plays no direct role in the synthesis of **gamma globulins**.

Q: What is the role of Factor X in the coagulation cascade?

Converts prothrombin to thrombin in the common pathway. ***Stuart-Prower factor*** - Factor X is also known as **Stuart-Prower factor**, essential for the common pathway of the coagulation cascade [1][2]. - It converts prothrombin to thrombin, facilitating the formation of **fibrin clots** [1]. - Factor X requires vitamin K for post-translational modification into its functional form [2]. *Tissue factor* - Tissue factor (TF) is involved in the **extrinsic pathway** of coagulation, activated by injury [1]. - It serves to initiate the clotting process by activating **Factor VII**, not Factor X directly [1]. *Christmas factor* - Christmas factor is another name for **Factor IX**, which plays a role in the intrinsic pathway of coagulation [1]. - It is primarily associated with **Hemophilia B**, whereas Factor X is part of the common pathway. *Hageman factor* - Hageman factor refers to **Factor XII**, which initiates the intrinsic pathway upon contact with negatively charged surfaces [1]. - It does not directly convert to Factor X in the clotting cascade. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Hemodynamic Disorders, Thromboembolic Disease, and Shock, pp. 128-130. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 582-583.

Q: Which of the following substances does hemoglobin not bind or transport?

SO2. **SO2** - **Sulfur dioxide (SO2)** is a toxic gas primarily associated with air pollution and **acid rain**; hemoglobin does not have a binding site for or physiological role in transporting SO2. - Exposure to SO2 can cause respiratory irritation and damage, but it does not directly bind to hemoglobin like CO, O2, or CO2. *CO* - **Carbon monoxide (CO)** binds to hemoglobin with an affinity 200-250 times greater than oxygen, forming **carboxyhemoglobin**. - This strong binding prevents oxygen transport, leading to **tissue hypoxia**. *O2* - **Oxygen (O2)** is the primary physiological ligand for hemoglobin, binding to the **heme iron** to be transported from the lungs to peripheral tissues, forming oxyhemoglobin. - This binding is cooperative, meaning the binding of one O2 molecule increases hemoglobin's affinity for subsequent O2 molecules. *CO2* - **Carbon dioxide (CO2)** is transported by hemoglobin, forming **carbaminohemoglobin**, though most CO2 is transported as bicarbonate. - CO2 binds to the **amino groups** of the globin chains, not the heme iron, making it a distinct binding site from oxygen.

Q: Which factor activates the extrinsic system of coagulation?

Factor III (Tissue factor). ***Factor III*** - The **extrinsic pathway** of coagulation is primarily activated by **tissue factor (Factor III)** in response to vascular injury [1]. - This pathway is crucial for initiating the coagulation cascade, leading to the conversion of **prothrombin to thrombin** [1,2]. *Factor X* - Factor X is part of the **common pathway** and is activated downstream after the extrinsic system is initiated, so it cannot activate the extrinsic pathway itself [2]. - It acts as a bridge between the **intrinsic** and **extrinsic pathways**, playing no direct role in their activation. *Factor XI* - Factor XI is involved in the **intrinsic pathway** and is activated by **thrombin** or contact activation, not directly related to the extrinsic pathway. - Its role in coagulation is primarily in amplifying the response after initial activation has occurred. *Factor XII* - Also part of the **intrinsic pathway**, Factor XII is activated by contact with negatively charged surfaces, thus does not have a role in the extrinsic pathway [2]. - Like Factor XI, its activation is indirectly linked to the extrinsic coagulation process, but it does not initiate it. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Hemodynamic Disorders, Thromboembolic Disease, and Shock, pp. 126-128. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Hemodynamic Disorders, Thromboembolic Disease, and Shock, pp. 128-130.

Q: NO acts on platelets through?

cGMP. ***cGMP*** - **Nitric oxide (NO)** activates **guanylyl cyclase**, which then converts **GTP (guanosine triphosphate)** to **cGMP (cyclic guanosine monophosphate)**. - Increased levels of **cGMP** in platelets lead to a cascade of events that ultimately result in **platelet inhibition**, mainly by reducing intracellular calcium and inhibiting aggregation. *cAMP* - **cAMP (cyclic AMP)** is primarily involved in pathways mediated by **prostacyclin (PGI2)** and **prostaglandin E1 (PGE1)**, which activate adenylyl cyclase. - While both **cAMP** and **cGMP** are cyclic nucleotides that regulate platelet function, **NO** specifically acts via the **cGMP** pathway. *Adenosine* - **Adenosine** acts on specific surface receptors (e.g., A2A receptors) on platelets, leading to activation of **adenylyl cyclase** and an increase in **cAMP** levels, which also inhibits platelet aggregation. - However, **NO** does not directly act through **adenosine** or its receptors to exert its effects. *TX-A2* - **Thromboxane A2 (TXA2)** is a potent **pro-aggregatory** and **vasoconstrictive** agent produced by platelets. - **NO** opposes the actions of **TXA2**; it does not act through it but rather counteracts its effects to promote platelet inhibition.

Q: In a blood typing test, no agglutination is observed with anti-A and anti-B antisera, but agglutination is observed with anti-D (Rh) antisera. What is the blood type?

O+ve. ***O+ve*** - No agglutination with **anti-A** and **anti-B antisera** indicates the absence of A and B antigens, characteristic of **blood group O**. - Agglutination with **anti-D (Rh) antisera** signifies the presence of the **Rh antigen**, thereby indicating a positive (+) blood type. *O-ve* - While no agglutination with anti-A and anti-B points to **blood group O**, no agglutination with **anti-D** would be expected for an Rh-negative type. - The observed agglutination with **anti-D** contradicts an Rh-negative classification. *A+ve* - Agglutination with **anti-A antisera** would be expected for an A blood type, which is not observed in this scenario. - While agglutination with **anti-D** is consistent with 'positive', the absence of agglutination with **anti-A** rules out 'A' blood group. *B-ve* - Agglutination with **anti-B antisera** would be expected for a B blood type, which is not observed in this scenario. - The agglutination with **anti-D** contradicts an Rh-negative classification, making **B-ve** incorrect.

Q: Nude mice are not resistant to xenografts due to absence of

T cell. ***T cell*** - Nude mice have a **congenital athymia**, meaning they lack a functional **thymus**. - The thymus is essential for the maturation and development of **T lymphocytes**, making these mice severely **T-cell deficient**. - Without functional T cells, nude mice cannot reject **xenografts** (tissue transplanted from a different species). *B cell* - While nude mice have impaired T-cell function, their **B-cell development and function remain largely intact**. - B cells develop in the **bone marrow** and do not require the thymus for maturation. - B cells alone are insufficient to reject xenografts, as this requires cell-mediated immunity. *Absence of both B and T cells* - This statement is incorrect because nude mice **do possess B cells**, even if their T-cell immunity is severely compromised. - The primary defect is in the **thymus**, affecting T-cell maturation, not B cells. - Complete absence of both would describe **SCID mice**, not nude mice. *Presence of both B and T cells* - This is incorrect as nude mice clearly have a **severe deficiency in T cells** due to athymia. - Their inability to reject xenografts is directly linked to this lack of functional T-cell immunity. - If both were present and functional, the mice would reject xenografts normally.

Q: Converging point of both pathways in coagulation is at:

Stuart factor X. ***Stuart factor X*** [1][2] - It is the main **converging point** of the coagulation cascade, where both the intrinsic and extrinsic pathways meet to initiate the common pathway [1]. - Activated factor X leads to the conversion of **prothrombin to thrombin**, pivotal for clot formation [2]. *Factor VII* [2] - Primarily involved in the **extrinsic pathway** of coagulation, activating factor X, but does not serve as a converging point. - Its function is limited to starting the coagulation cascade, particularly upon tissue injury. *Factor IX* [2] - A key component of the **intrinsic pathway**, it leads to the activation of factor X but is not the point where both pathways converge. - It requires **factor VIII** for its activation, further illustrating its role within a specific pathway. *Factor VIII* - Also part of the **intrinsic pathway**, it acts as a cofactor for factor IX but does not integrate both pathways into a common point. - Its deficiency is associated with **Hemophilia A**, underscoring its specific pathway involvement. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Hemodynamic Disorders, Thromboembolic Disease, and Shock, pp. 128-130. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 582-583.

Question 1

Which of the following mechanisms facilitates the delivery of oxygen in fetal circulation?

Accepted Answer

Higher affinity of HbF for O2

Answer

Haldane effect

Answer

Bohr's effect

Answer

None of the options

Question 2

Where is the primary site of synthesis for Complement component C1 inhibitor (C1-INH)?

Accepted Answer

Liver

Answer

Intestinal epithelium

Answer

Macrophages

Answer

Endothelium

Question 3

Gamma globulins are synthesized in?

Accepted Answer

Plasma cells

Answer

Liver

Answer

Spleen

Answer

Kidney

Question 4

What is the role of Factor X in the coagulation cascade?

Accepted Answer

Converts prothrombin to thrombin in the common pathway

Answer

Initiates the intrinsic pathway of coagulation

Answer

Activates Factor X in the intrinsic pathway

Answer

Serves as cofactor for Factor VII in extrinsic pathway

Question 5

Which of the following substances does hemoglobin not bind or transport?

Accepted Answer

SO2

Answer

CO

Answer

CO2

Answer

O2

Question 6

Which factor activates the extrinsic system of coagulation?

Accepted Answer

Factor III (Tissue factor)

Answer

Factor X (Stuart-Prower factor)

Answer

Factor XII (Hageman factor)

Answer

Factor XI (Plasma thromboplastin antecedent)

Question 7

NO acts on platelets through?

Accepted Answer

cGMP

Answer

Adenosine

Answer

cAMP

Answer

TX-A2

Question 8

In a blood typing test, no agglutination is observed with anti-A and anti-B antisera, but agglutination is observed with anti-D (Rh) antisera. What is the blood type?

Accepted Answer

O+ve

Answer

O-ve

Answer

A+ve

Answer

B-ve

Question 9

Nude mice are not resistant to xenografts due to absence of

Accepted Answer

T cell

Answer

B cell

Answer

Absence of both B and T cells

Answer

Presence of both B and T cells

Question 10

Converging point of both pathways in coagulation is at:

Accepted Answer

Stuart factor X

Answer

Factor VIII

Answer

Factor IX

Answer

Factor VII

Blood and Immunity — MCQs

Blood and Immunity — MCQs

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