In the 'salvage pathway' utilized during hybridoma selection, which enzyme is provided by the B-cell to allow survival in HAT medium?
- RNAse H
- HGPRT
- Dihydrofolate reductase
- DNA Polymerase III
Explanation: Hypoxanthine-guanine phosphoribosyltransferase (HGPRT) is the key enzyme for the salvage pathway. Myeloma cells are HGPRT-deficient; thus, only fusions with B-cells (which are HGPRT-positive) survive.
In the hybridoma method, unfused myeloma cells die in the HAT medium because they lack which metabolic enzyme?
- Amylase
- Ligase
- HGPRT
- Reverse Transcriptase
Explanation: Myeloma cells used for fusion are mutant strains that lack the HGPRT enzyme, preventing them from using the salvage pathway when the de novo pathway is blocked.
Which part of the antigen is physically recognized and bound by a monoclonal antibody?
- Epitope
- Isotype
- Genotype
- Paratope
Explanation: An epitope (or antigenic determinant) is the specific portion of an antigen molecule to which an antibody attaches itself.
Which component of an Antibody-Drug Conjugate (ADC) is responsible for ensuring the toxin is released only after entering the target cell?
- The PEG stabilizer
- The mAb vehicle
- The chemical linker
- The cytotoxic payload
Explanation: The linker holds the drug and antibody together. 'Cleavable linkers' are designed to break only under specific conditions found inside a cell (like acidic pH or specific enzymes).
Bispecific T-cell Engagers (BiTEs) are designed to bridge which two types of cells?
- Cancer cell and T-cell
- Neuron and Glial cell
- B-cell and Myeloma cell
- Red blood cell and Platelet
Explanation: BiTEs have two binding sites: one for a tumor antigen and one for the CD3 receptor on T-cells, physically bringing the immune system into contact with the cancer.
What happens during the 'De-novo' pathway of nucleotide synthesis that is blocked by Aminopterin in HAT medium?
- Breakdown of DNA molecules
- Synthesis from simple precursors
- Uptake of thymidine from the environment
- Recycling of old nucleotides
Explanation: The 'de novo' pathway builds nucleotides from scratch using amino acids and other precursors. Aminopterin blocks this, forcing cells to use the 'salvage' (recycling) pathway.
The monoclonal antibody Omalizumab is primarily used in the management of severe allergic asthma by targeting which isotype of immunoglobulin?
Explanation: Omalizumab binds to free IgE in the blood, preventing it from attaching to mast cells and triggering the allergic inflammatory cascade.
Which monoclonal antibody is used in cardiac interventions to prevent blood clots by blocking Glycoprotein IIb/IIIa receptors?
- Adalimumab
- Trastuzumab
- Infliximab
- Abciximab
Explanation: Abciximab is a chimeric mAb fragment used to prevent platelet aggregation and thrombus formation during percutaneous coronary intervention.
Which diagnostic technique employs monoclonal antibodies to detect specific proteins in a liquid sample through an enzyme-linked color change?
- ELISA
- Flow Cytometry
- RT-PCR
- Western Blot
Explanation: The Enzyme-Linked Immunosorbent Assay (ELISA) uses the high specificity of mAbs to capture antigens and produces a quantifiable color change via a linked enzyme.
In HAT medium selection, why do unfused B-cells naturally die off without the need for inhibitors?
- They have a short natural lifespan
- They are sensitive to thymidine
- They cannot use hypoxanthine
- They lack the HGPRT enzyme
Explanation: Normal B-lymphocytes do not divide indefinitely in culture and will die naturally within a few days, leaving only the immortalized hybridoma fusions.
A monoclonal antibody with the infix '-os-' (e.g., Denosumab) is designed to target which specific physiological system?
- Kidneys
- Nervous system
- Lungs
- Bone
Explanation: The infix '-os-' represents bone (osteal) targets. Denosumab, for instance, is used to treat osteoporosis and bone giant cell tumors.
In the nomenclature of monoclonal antibodies, the infix '-li-' (e.g., Infliximab) refers to which target system?
Explanation: The infix '-li-' refers to the immune system. For example, Infliximab is used in treating autoimmune diseases like Crohn's.
Monoclonal antibodies classified as 'Humanized' (-zumab) are engineered to be approximately what percentage human in their protein sequence?
Explanation: Humanized antibodies are roughly 90-95% human. Only the Complementarity Determining Regions (CDRs) of the variable loops are of mouse origin to maintain binding specificity.
If a monoclonal antibody has the suffix '-umab' (e.g., Denosumab), its genetic origin is:
- Humanized
- Fully Human
- Chimeric
- Bovine
Explanation: The suffix '-umab' identifies antibodies that are 100% human in sequence, usually produced in transgenic animals or through phage display.
Which monoclonal antibody targets the HER2 receptor in the treatment of aggressive breast cancer?
- Adalimumab
- Rituximab
- Infliximab
- Trastuzumab
Explanation: Trastuzumab (Herceptin) binds to the HER2/neu receptor, which is overexpressed in about 20-30% of breast cancers.
Which enzyme-linked technique is primarily used to confirm the presence of a specific protein in a complex tissue sample using monoclonal antibodies?
- Western Blotting
- Polymerase Chain Reaction
- Sanger Sequencing
- Northern Blotting
Explanation: Western blotting (immunoblotting) uses monoclonal antibodies to identify specific proteins from a mixture that has been separated by gel electrophoresis.
In the production of mAbs, the process of 'Limiting Dilution' is used to ensure that:
- The mouse survives the procedure
- The antibody is not too toxic
- The HAT medium is neutralized
- Each well contains only one cell
Explanation: Limiting dilution ensures that the resulting colonies are monoclonal (derived from a single cell), guaranteeing that the antibodies produced are identical.
The 'CDR' in humanized antibody engineering stands for:
- Complementarity Determining Region
- Circulatory Delivery Route
- Cellular Death Receptor
- Constant DNA Region
Explanation: CDRs are the hypervariable loops within the variable domains that physically contact the antigen and determine the specificity of the antibody.
In 'Immuno-affinity Chromatography', monoclonal antibodies are immobilized on a matrix primarily to perform:
- Cellular respiration
- Isotope labeling
- Protein purification
- DNA amplification
Explanation: This technique leverages the high specificity of mAbs to 'capture' a target protein from a complex biological mixture, allowing it to be isolated with high purity.
When a monoclonal antibody blocks a ligand from binding to its receptor, the mechanism is known as:
- Genetic recombination
- Apoptosis
- Signal transduction
- Competitive inhibition
Explanation: The antibody 'competes' for the same binding site as the natural ligand, thereby blocking the biological signal that would normally be triggered.
Which of the following is the primary physiological limitation of using first-generation 'Murine' (-omab) monoclonal antibodies in human clinical therapy?
- High risk of bacterial mutation
- Inability to bind human epitopes
- Lack of a heavy chain region
- Development of HAMA response
Explanation: Human Anti-Mouse Antibodies (HAMA) are produced when the patient's immune system recognizes mouse proteins as foreign, neutralizing the drug and potentially causing allergic reactions.
In the context of COVID-19 treatment, which monoclonal antibody was specifically designed to retain activity against the Omicron variant's highly mutated spike protein?
- Regdanvimab
- Sotrovimab
- Etesevimab
- Bamlanivimab
Explanation: Sotrovimab targets a highly conserved epitope on the SARS-CoV-2 spike protein that is less likely to mutate, allowing it to maintain effectiveness against several variants including early Omicron strains.
Which type of monoclonal antibody ends with the suffix '-omab'?
- Humanized
- Chimeric
- Murine
- Fully Human
Explanation: The '-omab' suffix is used for 100% mouse (murine) antibodies, which were the first generation of monoclonal therapies developed.
How do monoclonal antibodies differ from vaccines in the context of immunization?
- They provide passive immunity
- They contain live viruses
- They provide active immunity
- They last for several years
Explanation: Vaccines induce the body to create its own antibodies (active), whereas mAb therapy provides ready-made antibodies from an external source (passive).
Monoclonal antibodies used in 'Immuno-affinity chromatography' serve what primary laboratory purpose?
- Purifying molecules
- Measuring cell pH
- Sequencing proteins
- Visualizing nuclei
Explanation: mAbs are attached to a matrix to capture specific antigens from a complex mixture, allowing for high-level purification of biological substances.
Which part of the antibody molecule determines its 'Isotype' (e.g., IgG, IgM, IgA)?
- Variable Light chain
- Variable Heavy chain
- Hypervariable loop
- Constant Heavy chain
Explanation: The constant region of the heavy chain determines the class or isotype of the antibody, which in turn dictates its functional properties.
What is the primary reason monoclonal antibodies are stored in a 'Cold Chain' (2-8°C)?
- To keep the bacteria inside alive
- To prevent them from evaporating
- To prevent protein denaturation
- To increase their chemical reactivity
Explanation: Antibodies are complex proteins. High temperatures can cause them to unfold (denature) or aggregate, making them lose their binding specificity and efficacy.
Which of the following monoclonal antibody 'cocktails' was famously authorized for emergency use during the COVID-19 pandemic?
- REGEN-COV
- Herceptin-Plus
- Humira-DX
- Zevalin-90
Explanation: REGEN-COV was a combination of two mAbs (Casirivimab and Imdevimab) designed to prevent the virus from entering human cells.
Which monoclonal antibody targets the CTLA-4 receptor to 'release the brakes' on the immune system for cancer therapy?
- Rituximab
- Infliximab
- Ipilimumab
- Abciximab
Explanation: Ipilimumab is a checkpoint inhibitor that blocks CTLA-4, a molecule that normally downregulates the immune system, thereby enhancing the T-cell attack on cancer cells.
The 'Fc' region of a monoclonal antibody is constant within a species. What does 'Fc' stand for?
- Fragment crystallizable
- Fibrous complex
- Fast-acting component
- Functional core
Explanation: It is named 'crystallizable' because this part of the antibody molecule easily forms crystals when isolated in a laboratory setting.
In monoclonal nomenclature, the infix '-li-' (e.g., Belimumab) indicates that the drug targets which system?
- Lungs
- Immune system
- Circulatory system
- Liver
Explanation: The infix '-li-' (or '-lim-') stands for the immune system. Drugs with this infix are generally used for autoimmune or inflammatory conditions.
In hybridoma technology, why is it necessary to use myeloma cells that are HGPRT-deficient?
- To ensure they die in HAT
- To increase their growth rate
- To prevent them from fusing
- To allow them to secrete Ig
Explanation: If the myelomas were not HGPRT-deficient, unfused myeloma cells would survive in HAT medium, making it impossible to isolate the fused hybridoma cells.
What is the primary role of the 'Hinge Region' in a monoclonal antibody molecule?
- Providing flexibility for antigen binding
- Triggering the HAMA response
- Encoding the genetic sequence
- Determining the antibody isotype
Explanation: The hinge region is a flexible amino acid stretch that allows the two antigen-binding arms (Fabs) to move independently, facilitating binding to epitopes spaced at different distances.
Which specific chemical agent is added to the HAT medium to inhibit the 'de novo' synthesis of nucleotides in myeloma cells?
- Thymidine
- Polyethylene Glycol
- Aminopterin
- Hypoxanthine
Explanation: Aminopterin is a folic acid antagonist that blocks the de novo pathway. This forces cells to use the salvage pathway, which only successfully fused hybridomas can do.
Which specific post-translational modification is critical for the effector function of monoclonal antibodies and dictates their 'Biological Activity'?
- Methylation
- Glycosylation
- Acetylation
- Phosphorylation
Explanation: Glycosylation of the Fc region is essential for the antibody to interact with Fc receptors on immune cells. Variations in sugar patterns can significantly alter the drug's efficacy and safety.
What is the primary function of Polyethylene Glycol (PEG) in the laboratory production of monoclonal antibodies?
- Stabilizing the antibody shelf-life
- Inducing cell membrane fusion
- Sequencing the B-cell DNA
- Inhibiting bacterial growth
Explanation: PEG acts as a fusogen. It destabilizes the plasma membranes of B-cells and myeloma cells, allowing them to merge into a single hybridoma cell.
Monoclonal antibodies used as 'Check-point Inhibitors' (e.g., Pembrolizumab) primarily target which receptor to enhance the anti-tumor response?
Explanation: By blocking PD-1 (Programmed Death-1), these antibodies prevent cancer cells from 'turning off' T-cells, thereby restoring the immune system's ability to attack the tumor.
Which monoclonal antibody was the first to be approved for treating 'wet' Age-related Macular Degeneration (AMD) by inhibiting VEGF?
- Infliximab
- Ranibizumab
- Adalimumab
- Rituximab
Explanation: Ranibizumab (Lucentis) is a mAb fragment designed to bind to VEGF in the eye, preventing the growth of abnormal blood vessels that cause vision loss in AMD.
What is the primary function of the 'variable domain' in an antibody's light and heavy chains?
- Antigen recognition
- Activating complement
- Stabilizing the molecule
- Binding to the liver
Explanation: The variable domains contain the unique amino acid sequences that form the paratope, allowing the antibody to recognize its specific target.
Transgenic mice used for mAb production are unique because their own antibody-producing genes have been:
- Doubled in number
- Relocated to the liver
- Converted to RNA
- Inactivated and replaced
Explanation: Transgenic mice like 'XenoMouse' have had their endogenous murine antibody genes inactivated and replaced with human immunoglobulin gene loci.
Which of the following describes 'Phage Display' in the development of human monoclonal antibodies?
- Using bacteria to eat tumors
- Labeling antibodies with phages
- Selecting antibodies from a library
- Breeding phage-resistant mice
Explanation: Phage display is an in vitro technique where antibody fragments are displayed on the surface of viruses (phages) to screen for the best binders.
A 'Biosimilar' monoclonal antibody is essentially:
- A highly similar biological version
- A preventative vaccine
- A cheaper chemical copy
- A completely new drug class
Explanation: Unlike generic drugs (which are identical chemicals), biosimilars are biological products that are highly similar to an already approved 'reference' biologic.
A 'Chimeric' antibody (-ximab) is typically composed of which structural arrangement?
- Mouse Variable / Human Constant
- Rat Variable / Mouse Variable
- All Human Variable / No Constant
- Human Variable / Mouse Constant
Explanation: Chimeric antibodies fuse the antigen-binding variable regions from a mouse with the effector constant regions from a human to reduce immunogenicity.
The 'Complementarity Determining Regions' (CDRs) that define the specificity of a mAb are located within which segments of the antibody?
- Hinge regions of the molecule
- Fc region of the light chain
- Constant regions of heavy chains
- Variable regions of both chains
Explanation: CDRs are hypervariable loops found in the variable domains of both light and heavy chains. They provide the 'fit' required to bind to a specific antigen.
Which scientist shared the 1984 Nobel Prize with Köhler and Milstein for his theoretical work on the immune system's specificity?
- Robert Koch
- Louis Pasteur
- Paul Ehrlich
- Niels Jerne
Explanation: Niels K. Jerne was awarded the Nobel Prize for his theories concerning the specificity in development and control of the immune system.
Why is 'Phage Display' often preferred over hybridoma technology for developing fully human monoclonal antibodies?
- It requires fewer animals
- It uses plant-based cells
- It is significantly slower
- It bypasses in vitro screening
Explanation: Phage display is an in vitro technique that allows for the selection of human antibody fragments from massive libraries without the need for animal immunization.
The nomenclature infix '-vi-' in a drug like Palivizumab indicates that the monoclonal antibody targets which category of pathogens?
- Viral particles
- Tumor antigens
- Bacterial toxins
- Fungal spores
Explanation: In naming conventions, '-vi-' stands for viral, '-li-' for immune system, '-ba-' for bacterial, and '-tu-' for tumor targets.
The drug Rituximab, which targets the CD20 antigen, is primarily used for the treatment of which clinical condition?
- Viral Hepatitis
- Septic Shock
- B-cell Lymphoma
- Type 2 Diabetes
Explanation: Rituximab is a chimeric mAb that binds to CD20 on the surface of B-cells, marking them for destruction by the patient's immune system.
The 'Hybridoma' cell is a fusion product. Which of its parents provides the machinery for continuous antibody secretion?
- T-helper cell
- Macrophage
- B-lymphocyte
- Myeloma cell
Explanation: The B-cell (specifically a plasma cell) provides the genetic information and machinery to produce a specific antibody, while the myeloma cell provides the ability to divide indefinitely.
In 'Bispecific' monoclonal antibody technology, the resulting molecule is unique because it possesses:
- Dual radioactive tracers
- Zero constant regions
- Two different heavy chains
- Two different paratopes
Explanation: Bispecific antibodies are engineered to bind two different antigens simultaneously, such as one arm binding to a tumor cell and the other to a T-cell.
Fully human monoclonal antibodies are often produced via 'Transgenic Mice'. These mice are unique because:
- They carry human antibody genes
- They only live for 72 hours
- They lack an immune system
- They are clones of humans
Explanation: Transgenic mice have their own antibody-producing genes 'knocked out' and replaced with the human immunoglobulin gene loci, allowing them to produce human antibodies upon immunization.
The mechanism of 'Antibody-Dependent Cellular Cytotoxicity' (ADCC) is primarily mediated by which region of the monoclonal antibody?
- Paratope
- Fc region
- Fab fragment
- Variable domain
Explanation: The Fc (Fragment crystallizable) region interacts with Fc receptors on effector cells like Natural Killer (NK) cells to trigger the destruction of the target cell.
Which revolutionary mAb treatment for Alzheimer’s disease targets the amyloid-beta plaques in the brain?
- Aducanumab
- Abciximab
- Adalimumab
- Alemtuzumab
Explanation: Aducanumab was one of the first monoclonal antibodies to receive controversial FDA approval for targeting the underlying pathology of Alzheimer's.
In India, which regulatory body is responsible for granting approval for the manufacturing and clinical trial of 'Biosimilar' monoclonal antibodies?
- FSSAI
- CDSCO
- ICMR
- NITI Aayog
Explanation: The Central Drugs Standard Control Organisation (CDSCO), headed by the Drugs Controller General of India (DCGI), is the national regulatory authority for biopharmaceuticals.
Which mAb was the first to be approved for 'Anti-angiogenic' therapy by inhibiting Vascular Endothelial Growth Factor (VEGF)?
- Panitumumab
- Bevacizumab
- Ocrelizumab
- Cetuximab
Explanation: Bevacizumab (Avastin) prevents tumors from growing new blood vessels, thereby starving them of the oxygen and nutrients needed for growth.
The term 'Magic Bullet', popularized by Paul Ehrlich, refers to a drug that can kill a pathogen without harming the host. Which modern mAb class best exemplifies this?
- Murine IgG monomers
- Antibody-Drug Conjugates
- Unconjugated Fc-fusions
- Polyclonal serums
Explanation: Antibody-Drug Conjugates (ADCs) consist of a mAb linked to a cytotoxic drug. The mAb ensures the 'poison' is delivered only to cells expressing a specific target antigen.
What is the primary role of the 'Feeder Layer' in the early stages of hybridoma cell culture?
- Inducing cell death
- Kicking off DNA repair
- Providing growth factors
- Synthesizing the antibodies
Explanation: Feeder layers (often peritoneal macrophages) provide essential cytokines and growth factors to support the growth of single hybridoma cells after fusion.
Which of the following is a key advantage of 'Fully Human' antibodies over 'Humanized' antibodies?
- Higher antigen affinity
- Lowest possible immunogenicity
- Zero risk of any side effects
- Faster chemical synthesis
Explanation: Fully human antibodies (-umab) contain no non-human protein sequences, making them the least likely to be recognized as foreign by the human immune system compared to chimeric or humanized versions.
Which of the following describes the 'Paratope' of a monoclonal antibody?
- The antibody's binding site
- The antigen's binding site
- The heavy chain's tail
- The cellular DNA locus
Explanation: The paratope is the specific part of the antibody (located in the variable region) that recognizes and binds to the epitope on the antigen.
What is the typical 'Half-life' of a fully human monoclonal antibody in the human bloodstream?
- 2 hours
- 21 days
- 12 hours
- 3 days
Explanation: Human IgG antibodies have a long half-life (approx. 3 weeks) due to their ability to be recycled by the neonatal Fc receptor (FcRn).