Weekly Year 2: Cellular Immunology Exam - May 1, 2026 (Secti

Question 1

Which of the following techniques commonly uses ultraviolet (UV) light for examining specimens, often to visualize fluorescently labeled antibodies or cellular components?

Accepted Answer

Fluorescence microscopy — Fluorescence microscopy utilizes UV light to excite fluorophores, which then emit visible light, allowing for the visualization of specific labeled structures or antibodies.

Question 2

Which of the following methods would typically be employed as a preliminary screening test for the presence of antibodies to HIV proteins in a patient's blood sample due to its high sensitivity and cost-effectiveness?

Accepted Answer

Enzyme-Linked Immunosorbent Assay (ELISA) — ELISA (Enzyme-Linked Immunosorbent Assay) is widely used for preliminary screening of antibodies due to its sensitivity and suitability for high-throughput testing. Western blot is typically used for confirmation.

Question 3

What color light is typically emitted when antigens are detected using fluorescein isothiocyanate (FITC) as a fluorescent label, such as in direct or indirect immunofluorescence assays?

Accepted Answer

Green — Fluorescein isothiocyanate (FITC) is a common fluorophore that, when excited by UV light, emits a characteristic green light.

Question 4

Which of the following immunoassays commonly utilizes the enzyme horseradish peroxidase (HRP) as a detection label, often conjugated to a secondary antibody, to produce a measurable signal?

Accepted Answer

Enzyme-Linked Immunosorbent Assay (ELISA) — Horseradish peroxidase (HRP) is a widely used enzyme label in ELISA, Western blot, and immunohistochemistry. It catalyzes a reaction with a substrate to produce a colored, fluorescent, or luminescent product.

Question 5

Which of the following techniques is extensively used to detect specific antigens in cells or tissue sections, as well as to screen for auto-antibodies to cellular or tissue antigens in clinical diagnostics?

Accepted Answer

Immunofluorescence — Immunofluorescence allows for the visualization of antigens in situ within cells or tissues by using fluorescently labeled antibodies. It's also used to detect autoantibodies that bind to tissue antigens.

Question 6

Which of the following laboratory techniques utilizes protein antigens separated by molecular weight using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) prior to detection with specific antibodies?

Accepted Answer

Western blot — Western blot involves separating proteins by size via SDS-PAGE, transferring them to a membrane, and then detecting specific proteins (antigens) using antibodies, often labeled with HRP or a fluorophore.

Question 7

Each polypeptide chain (heavy and light) on an immunoglobulin molecule consists of which two distinct functional and structural regions?

Accepted Answer

Variable (V) and Constant (C) regions — Immunoglobulin heavy and light chains each have a Variable (V) region, which contributes to antigen binding specificity, and a Constant (C) region, which mediates effector functions or provides structural support.

Question 8

In somatic recombination during B cell development, which gene locus rearranges first? And which region of the antibody molecule is primarily generated via this recombination, determining antigen binding specificity?

Accepted Answer

Heavy chain; Variable region — During somatic recombination (V(D)J recombination), the heavy chain gene segments rearrange first, followed by the light chain. This process generates the diverse Variable (V) regions responsible for antigen binding.

Question 9

What are the two main types of light chains found in human immunoglobulins?

Accepted Answer

Kappa and Lambda — Human immunoglobulins contain either kappa (κ) or lambda (λ) light chains. A single antibody molecule will have two identical kappa or two identical lambda light chains.

Question 10

Which of the following statements is NOT true regarding the mechanisms that generate antibody diversity?

Accepted Answer

Class switching (isotype switching) directly alters the antigen-binding specificity of an antibody. — Class switching alters the constant region of the heavy chain, thereby changing the antibody's effector function (isotype), but it does not change the variable region or the antigen-binding specificity. Antigen-binding specificity is determined by the V(D)J regions.

Question 11

Which two immunoglobulin isotypes are frequently found co-expressed on the surface of mature B cells, possessing identical antigen-binding specificity, primarily through alternative processing of a primary RNA transcript rather than through class switching?

Accepted Answer

IgM and IgD — Mature, naive B cells co-express membrane-bound IgM and IgD with the same antigen specificity. This co-expression is achieved by alternative splicing and polyadenylation of the same primary RNA transcript, not by DNA recombination (class switching).

Question 12

If alternative processing of a primary B cell RNA transcript uses the first (proximal) polyadenylation site, what type of heavy chain mRNA is typically derived, leading to the production of secreted immunoglobulin?

Accepted Answer

Secreted heavy chain mRNA — The use of the first (proximal) polyadenylation site in the primary RNA transcript results in an mRNA that lacks the transmembrane domain exons, leading to the synthesis of a secreted heavy chain.

Question 13

Phagocytic white cells (leukocytes, e.g., macrophages) commonly congregate within which structures or locations when foreign organisms penetrate the skin through a cut?

Accepted Answer

Regional lymph nodes — Macrophages and other phagocytes are recruited to the site of infection in the skin. Antigens and activated immune cells then drain to regional lymph nodes, where immune responses are initiated.

Question 14

Which of the following mediators plays a crucial role in orchestrating an early, non-specific response to viral infections by the innate immune system, inducing an antiviral state in host cells?

Accepted Answer

Type I interferons (IFN-alpha/beta) — Type I interferons (IFN-α and IFN-β) are cytokines produced early in viral infections by infected cells and other immune cells. They induce an antiviral state in neighboring cells and activate innate immune cells.

Question 15

Which of the following cell types is a key messenger that mediates the crucial connection and communication between the innate and adaptive immune systems, particularly by presenting processed antigens to naive T cells?

Accepted Answer

Dendritic cells — Dendritic cells are the most potent professional antigen-presenting cells (APCs). They capture antigens in tissues, migrate to lymphoid organs, and present these antigens to naive T cells, thereby initiating adaptive immune responses.

Question 16

Which of the following immune system components would NOT directly recognize a specific macromolecule epitope (antigenic binding site) in a lock-and-key fashion?

Accepted Answer

Complement factor C3b alone — TCRs, BCRs, and free antibodies are designed to specifically recognize and bind to unique epitopes. Complement factor C3b binds to pathogen surfaces or immune complexes, but it is not a receptor that recognizes specific epitopes in the same way as adaptive immune receptors.

Question 17

Which of the following refers to a large genomic region or gene family found in most vertebrates, playing an absolutely critical role in immunity by encoding proteins involved in antigen presentation to T cells?

Accepted Answer

Major Histocompatibility Complex (MHC) — The Major Histocompatibility Complex (MHC) is a gene family that encodes MHC class I and II molecules, which are essential for presenting peptide antigens to T cells and initiating adaptive immune responses.

Question 18

T cells are primarily produced in the and subsequently migrate to complete their differentiation and maturation in the .

Accepted Answer

Bone marrow; Thymus — T cells originate as hematopoietic stem cells in the bone marrow, then travel to the thymus to undergo a complex maturation process, including positive and negative selection.

Question 19

Which of the following is a transmembrane glycoprotein that serves as a co-receptor for the T cell receptor (TCR) and is characteristically expressed on cytotoxic T cells (CTLs), playing a key role in recognizing MHC class I-bound antigens?

Accepted Answer

CD8 — CD8 is a co-receptor found on cytotoxic T cells (CTLs). It binds to MHC class I molecules on antigen-presenting cells, enhancing the sensitivity of the TCR's recognition of the antigen.

Question 20

Which of the following cell types is responsible for producing large amounts of antibodies (immunoglobulins) and differentiates from B cells upon appropriate stimulation, often requiring help from CD4+ T helper cells?

Accepted Answer

Plasma cells — Plasma cells are fully differentiated B cells specialized in secreting large quantities of antibodies. They are formed after B cell activation and differentiation, often with T cell help.

Question 21

Which of the following is a glycoprotein expressed on the surface of T helper cells, regulatory T cells, monocytes, macrophages, and dendritic cells, serving as a co-receptor for the TCR and binding to MHC class II molecules?

Accepted Answer

CD4 — CD4 is a co-receptor found on T helper cells, regulatory T cells, and various myeloid cells. It binds to MHC class II molecules, which present extracellular antigens to T helper cells.

Question 22

Which of the following types of antigen-presenting cells (APCs) is considered critical in the initial uptake and presentation of various antigens to naive T cells, especially in peripheral lymphoid organs?

Accepted Answer

Dendritic cells — Dendritic cells are the most effective APCs for activating naive T cells, initiating primary adaptive immune responses in lymph nodes.

Question 23

Which of the following types of antigen-presenting cells (APCs) utilizes its surface immunoglobulin (B cell receptor) to specifically bind an antigen, after which the antigen is internalized, degraded, and presented to T cells?

Accepted Answer

B cells — B cells can act as APCs by using their highly specific surface immunoglobulin (BCR) to capture soluble antigens, internalize them, and then present peptide fragments on MHC class II molecules to T helper cells.

Question 24

Which of the following types of antigen-presenting cells (APCs) is particularly specialized for the phagocytosis, degradation, and presentation of particulate antigens (e.g., bacteria, cellular debris) to T cells, especially in later stages of immune responses?

Accepted Answer

Macrophages — Macrophages are highly phagocytic cells that are crucial for clearing pathogens and cellular debris. They can also process and present antigens, particularly particulate antigens, to activated T cells.

Question 25

In liver cells, bilirubin is mainly conjugated with which of the following molecules to render it water-soluble and facilitate its excretion from the body?

Accepted Answer

Glucuronic acid — Bilirubin is conjugated with glucuronic acid in the liver to form bilirubin diglucuronide (conjugated bilirubin), making it water-soluble and allowing it to be excreted in bile.

Question 26

Which of the following metabolic pathways are crucial for providing energy and maintaining the integrity of mature red blood cells, which lack mitochondria and a nucleus?

Accepted Answer

Glycolysis and Pentose Phosphate Pathway (HMP Shunt) — Red blood cells rely on anaerobic glycolysis for ATP production (energy) and the pentose phosphate pathway (HMP shunt) for NADPH, which is essential for reducing oxidative stress and maintaining hemoglobin in its functional state.

Question 27

An abnormal increase in red blood cell count, often leading to increased blood viscosity and potential for clot formation, is clinically characterized by which of the following terms?

Accepted Answer

Polycythemia — Polycythemia refers to an increase in the total red blood cell mass, leading to a higher hematocrit and increased blood viscosity.

Question 28

Under normal physiological conditions, which of the following is the brain's preferred and primary source of energy?

Accepted Answer

Glucose — The brain primarily relies on glucose as its energy source. During prolonged starvation, it can adapt to use ketone bodies.

Question 29

Which of these statements is TRUE regarding hemolytic disease of the newborn (HDN)?

Accepted Answer

It is caused by maternal antibodies attacking fetal red blood cells, typically due to Rh incompatibility. — HDN (or erythroblastosis fetalis) is caused by maternal antibodies (usually anti-RhD) crossing the placenta and lysing fetal red blood cells. This typically occurs in Rh-negative mothers previously sensitized to Rh-positive fetal blood, often in a subsequent pregnancy. Rh immunoglobulin (Rhogam) is administered to the mother to prevent sensitization.

Question 30

Hematocrit is a measure of which of the following components of blood?

Accepted Answer

The percentage of blood volume occupied by red blood cells. — Hematocrit (Hct) represents the volume percentage of red blood cells (erythrocytes) in whole blood.

Question 31

For instant human muscle contraction requiring very rapid ATP resynthesis, high-energy phosphate bonds are readily provided by which of the following molecules?

Accepted Answer

Creatine phosphate — Creatine phosphate (phosphocreatine) acts as an immediate reserve of high-energy phosphate, rapidly transferring its phosphate group to ADP to resynthesize ATP during intense, short bursts of muscular activity.

Question 32

The Rapapport-Luebering cycle, which is important for regulating oxygen delivery by red blood cells through the production of 2,3-bisphosphoglycerate (2,3-BPG), is mainly located in which cellular compartment?

Accepted Answer

Red blood cell cytoplasm — The Rapapport-Luebering cycle is a shunt pathway within the glycolytic pathway that operates specifically in the cytoplasm of red blood cells to produce 2,3-BPG, which modulates hemoglobin's oxygen affinity.

Question 33

In adult humans, the major physiological site of erythrocyte production (erythropoiesis) is which of the following?

Accepted Answer

Bone marrow — In adults, the red bone marrow is the primary site of hematopoiesis, including the production of erythrocytes. The liver and spleen can be sites of extramedullary hematopoiesis under certain pathological conditions.

Question 34

During very short bursts of intense exercise (e.g., a sprint), which of the following represents the most rapid method to resynthesize ATP for muscle contraction?

Accepted Answer

Creatine phosphate system — The creatine phosphate system provides the most immediate and rapid source of ATP for muscle contraction by directly phosphorylating ADP, preceding glycolysis and aerobic respiration in very short, high-intensity activities.

Question 35

Which of the following diseases primarily affects neutrophil function, leading to recurrent severe bacterial and fungal infections due to an inability of phagocytes to produce reactive oxygen species?

Accepted Answer

X-linked agammaglobulinemia — Chronic Granulomatous Disease (CGD) is a primary immunodeficiency characterized by defects in NADPH oxidase, impairing phagocytes' ability to produce a respiratory burst and kill ingested microbes effectively.

Weekly Year 2: Cellular Immunology Exam - May 1, 2026 (Secti

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