Weekly Year 2: Cellular Immunology Exam - April 10, 2026 (Se

Question 1

Which of the following microscopy techniques uses ultraviolet (UV) light for examining specimens?

Accepted Answer

Fluorescence microscopy — Fluorescence microscopy uses UV light to excite fluorochromes like FITC to emit visible light.

Question 2

Which of the following serves as the standard preliminary screening for antibodies to HIV proteins in a patient's blood sample?

Accepted Answer

ELISA (Enzyme-Linked Immunosorbent Assay) — ELISA is the high-sensitivity screening tool used for HIV antibodies before confirmation via more specific tests.

Question 3

What color light is emitted when antigens treated with fluorescein isothiocyanate (FITC) are exposed to UV light?

Accepted Answer

Apple-green — FITC typically emits a bright apple-green fluorescence under UV light.

Question 4

Which of the following laboratory techniques utilizes the enzyme horseradish peroxidase (HRP)?

Accepted Answer

ELISA and Immunohistochemistry — HRP is commonly conjugated to antibodies in ELISA and IHC for colorimetric signal detection.

Question 5

Which technique is used extensively to detect antigens in tissue sections and screen for auto-antibodies?

Accepted Answer

Immunofluorescence (IF) — Immunofluorescence is the gold standard for visualizing antigens in situ within tissue biopsies.

Question 6

Which of the following uses protein antigens separated by molecular weight using SDS-PAGE?

Accepted Answer

Western Blot — Western blotting involves separating proteins by size via SDS-PAGE before transferring to a membrane for antibody probing.

Question 7

Each polypeptide chain (heavy and light) on an immunoglobulin molecule consists of a variable (V) region and a region.

Accepted Answer

Constant (C) — Antibody chains are composed of V regions (antigen binding) and C regions (effector function).

Question 8

In somatic recombination of the heavy chain, which segments rearrange first?

Accepted Answer

D and J — In B cell development, the D (Diversity) and J (Joining) segments of the heavy chain rearrange before V connects to DJ.

Question 9

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

Accepted Answer

Kappa and Lambda — Human antibodies use either Kappa or Lambda light chains, never both on one molecule.

Question 10

Which of the following is NOT true regarding the mechanisms of generating antibody diversity?

Accepted Answer

Alternative RNA splicing of V segments — V-D-J joining occurs at the DNA level (recombination), not through RNA splicing.

Question 11

Which two classes of antibodies are co-expressed on mature B cells via alternative RNA processing?

Accepted Answer

IgM and IgD — Naive mature B cells express both IgM and IgD with the same antigen specificity by alternative splicing of a primary transcript.

Question 12

If alternative processing of the heavy chain primary transcript uses the first polyadenylation site, which type of heavy chain is produced?

Accepted Answer

Secreted IgM — Cleavage at the first polyadenylation site removes membrane-anchoring exons, resulting in secreted antibody.

Question 13

In liver cells, bilirubin is mainly conjugated with which substance to increase solubility?

Accepted Answer

Glucuronic acid — Bilirubin is conjugated with glucuronic acid by the enzyme UDP-glucuronosyltransferase.

Question 14

Which of the following pathways are critical for Red Blood Cell (RBC) energy metabolism because they lack mitochondria?

Accepted Answer

Anaerobic Glycolysis (Embden-Meyerhof pathway) — Mature RBCs lack mitochondria and rely entirely on anaerobic glycolysis for ATP.

Question 15

An abnormal increase in the red blood cell count is known as:

Accepted Answer

Polycythemia — Polycythemia refers to an increased concentration of hemoglobin and/or RBCs.

Question 16

Which of the following is the brain’s preferred source of energy under normal physiological conditions?

Accepted Answer

Glucose — Glucose is the primary fuel for the brain; ketone bodies are used only during prolonged starvation.

Question 17

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

Accepted Answer

It occurs when an Rh- mother carries an Rh+ fetus — HDN typically involves Rh- mothers becoming sensitized to Rh+ fetal RBCs, producing IgG that crosses the placenta.

Question 18

Hematocrit is a direct measure of:

Accepted Answer

The percentage of blood volume occupied by red blood cells — Hematocrit represents the volume of packed red cells in a blood sample.

Question 19

High-energy phosphate bonds for instant muscle contraction are provided by:

Accepted Answer

Phosphocreatine (Creatine Phosphate) — Phosphocreatine provides the most rapid mobilization of high-energy phosphates to regenerate ATP.

Question 20

The Rapapport-Luebering cycle, which produces 2,3-BPG, is located in:

Accepted Answer

Erythrocytes — The Rapoport-Luebering shunt is a pathway in RBCs used to regulate oxygen affinity for hemoglobin.

Question 21

In adult humans, the major site of erythrocyte production is the:

Accepted Answer

Red bone marrow — In adults, hematopoiesis occurs primarily in the red bone marrow of flat and long bones.

Question 22

Where do phagocytic leukocytes like macrophages congregate when foreign organisms breach the skin?

Accepted Answer

Sites of inflammation — Macrophages migrate to and congregate at the site of infection/injury (inflammation) in response to chemotactic signals.

Question 23

Which of the following mediates an early response to viral infections by the innate immune system?

Accepted Answer

Type I Interferons (IFN-α/β) — Interferons alpha and beta are secreted by virally infected cells to induce an anti-viral state in neighboring cells.

Question 24

Which chemical messengers mediate the link between the innate and adaptive immune systems?

Accepted Answer

Cytokines/Chemokines — Cytokines and chemokines secreted by innate cells (like DCs) help activate and direct the adaptive T and B cell responses.

Question 25

Which of the following immune components would NOT typically recognize a macromolecule epitope directly?

Accepted Answer

T cell receptor (TCR) — TCRs generally recognize processed peptide fragments presented on MHC molecules, not intact macromolecules.

Question 26

Which genomic region plays a central role in vertebrate immunity by encoding molecules that present antigens?

Accepted Answer

The Major Histocompatibility Complex (MHC) — MHC (HLA in humans) is critical for presenting antigens to T cells.

Question 27

T cells are produced in the and complete their differentiation in the .

Accepted Answer

Bone marrow / Thymus — Lymphoid progenitors originate in the bone marrow but migrate to the thymus for T-cell maturation.

Question 28

Which transmembrane glycoprotein serves as a co-receptor for MHC Class I and identifies Cytotoxic T Cells?

Accepted Answer

CD8 — CD8 is the co-receptor for MHC I and is the definitive marker for cytotoxic T lymphocytes (CTLs).

Question 29

Which cells differentiate into plasma cells to produce large amounts of antibodies?

Accepted Answer

B cells — B cells differentiate into plasma cells upon activation to secrete immunoglobulins.

Question 30

Which glycoprotein is a co-receptor for MHC Class II and is found on T helper cells?

Accepted Answer

CD4 — CD4 is the marker for T helper cells and binds to MHC Class II molecules.

Question 31

Which antigen-presenting cell (APC) is specialized for the uptake and initial presentation of antigen to naive T cells?

Accepted Answer

Dendritic Cell — Dendritic cells are the most potent professional APCs for activating naive T cells.

Question 32

Which APC uses surface immunoglobulin as a receptor to internalize specific antigens for presentation?

Accepted Answer

B Cell — B cells use their BCR (membrane-bound Ig) to capture specific antigens for processing and presentation to T cells.

Question 33

Which APC is specialized for the degradation and presentation of particulate and fungal antigens?

Accepted Answer

Macrophage — Macrophages are professional phagocytes specialized in engulfing and degrading particulate matter.

Question 34

The RAG-1 and RAG-2 enzymes are essential for which process?

Accepted Answer

V(D)J recombination — Recombination-Activating Genes (RAG) are required for the DNA rearrangement of TCR and BCR gene segments.

Question 35

Which of the following is FALSE regarding skeletal muscle metabolism?

Accepted Answer

It can release free glucose into the blood from glycogen — Skeletal muscle lacks glucose-6-phosphatase; therefore, it cannot release free glucose into the blood; it uses glucose-6-phosphate locally.

Question 36

The process of programmed cell death used to eliminate self-reactive lymphocytes is called:

Accepted Answer

Apoptosis — Apoptosis is the mechanism of clonal deletion in central and peripheral tolerance.

Question 37

Which antibody isotype is the first to be produced during a primary immune response?

Accepted Answer

IgM — IgM is the initial isotype produced before class switching occurs.

Question 38

In the context of blood banking, an individual with Type O blood has which antibodies in their serum?

Accepted Answer

Both Anti-A and Anti-B — Type O individuals lack A and B antigens and therefore possess antibodies against both.

Question 39

Which enzyme in the RBC prevents oxidative damage by reducing methemoglobin?

Accepted Answer

Methemoglobin reductase — NADH-dependent methemoglobin reductase maintains iron in the ferrous (Fe2+) state.

Question 40

Which part of the antibody molecule determines its isotype (e.g., IgG vs IgA)?

Accepted Answer

The Constant region of the Heavy chain — The heavy chain's constant region (mu, delta, gamma, alpha, or epsilon) defines the antibody class.

Question 41

MHC Class I molecules present endogenous antigens to:

Accepted Answer

CD8+ T cells — MHC Class I presents intracellular peptides to cytotoxic CD8+ T cells.

Question 42

MHC Class II molecules are primarily found on:

Accepted Answer

Professional Antigen Presenting Cells (APCs) — MHC II expression is restricted to APCs like DCs, macrophages, and B cells.

Question 43

The 'J chain' is a polypeptide associated with which antibody structures?

Accepted Answer

Polymeric IgM and IgA — The J (joining) chain is required to stabilize pentameric IgM and dimeric IgA.

Question 44

Which of the following is associated with the 'oxygen debt' following intense exercise?

Accepted Answer

Lactic acid conversion to glucose (Cori Cycle) — Oxygen debt is partly due to the metabolic cost of converting lactate back to glucose/glycogen in the liver.

Question 45

What is the primary function of 2,3-bisphosphoglycerate (2,3-BPG) in the RBC?

Accepted Answer

Decreasing hemoglobin's affinity for oxygen — 2,3-BPG binds to hemoglobin and promotes oxygen unloading at the tissues.

Question 46

Hypervariable regions (CDRs) are found within:

Accepted Answer

The Variable domains of both heavy and light chains — Complementarity Determining Regions (CDRs) provide the specificity for antigen binding.

Question 47

Which cells serve as the link between the innate and adaptive immune systems by migrating to lymph nodes?

Accepted Answer

Dendritic cells — DCs capture antigen in tissues and migrate to secondary lymphoid organs to activate T cells.

Question 48

During B cell development, 'Negative Selection' refers to:

Accepted Answer

The deletion of B cells that react strongly to self-antigens — Negative selection ensures self-tolerance by eliminating auto-reactive lymphocytes.

Question 49

Which of the following is an example of a PAMP (Pathogen-Associated Molecular Pattern)?

Accepted Answer

Lipopolysaccharide (LPS) — LPS from gram-negative bacteria is a classic PAMP recognized by TLR4.

Question 50

The Pentose Phosphate Pathway in RBCs is essential for generating:

Accepted Answer

NADPH — NADPH is required to maintain reduced glutathione, which protects the RBC from oxidative stress.

Weekly Year 2: Cellular Immunology Exam - April 10, 2026 (Se

Questions, Answers & Explanations