Lecture 25: Humoral Immunity II: Antibody Effector Functions

Which characteristic is most likely to make an antigen a strong immunogen?

What is the primary function of class switch recombination (CSR)?

Which of the following is NOT a major mechanism of antibody effector function?

Which antibody isotype is MOST associated with allergic responses?

What is a key characteristic of haptens?

Which factor is LEAST likely to affect the immunogenicity of an antigen?

What is the primary role of circulating antibodies?

Where does class switch recombination (CSR) occur?

Which enzyme is essential for the process of class switch recombination (CSR)?

Following activation by antigen, what is the immediate fate of IgM and IgD produced within a B cell?

Which statement accurately describes the function of the secretory component associated with IgA?

Which antibody isotype is transported across the placenta to provide passive immunity to the developing fetus?

What is the primary mechanism by which IgA protects mucosal surfaces?

How does IgM initiate the classical pathway of complement activation?

An individual is bitten by a venomous snake. Which therapeutic approach would MOST directly employ neutralization?

What is the role of Fc receptors in antibody-mediated effector functions?

What is the correct order of events in the classical pathway of complement activation, beginning with antibody binding?

Which of the following is true regarding the transport of IgG across the placenta?

Which process BEST describes how antibodies contribute to the neutralization of a virus?

In antibody-dependent cell cytotoxicity (ADCC), which cell type is MOST critical for mediating the killing of target cells?

An individual with a genetic defect has a complete absence of Fc&RI (Fc epsilon receptor I). Which immune function would be MOST impaired in this individual?

Which characteristic distinguishes IgA1 from IgA2?

After the classical C3 convertase (C4bC2a) is formed, what is its DIRECT enzymatic activity?

What is the MAIN role of C3b in complement activation?

How are immune complexes (ICs) removed from circulation?

Which statement is TRUE regarding fetal and neonatal immunity?

Which cytokine involved in class switch recombination biases towards IgE and IgG4?

What is the implication of low molecular weight for a potential immunogen?

How does the 'staple' form of IgM contribute to complement activation?

If C4bC2a is the classical C3 convertase, what is the alternative C3 convertase?

During an infection, an individual's B cells undergo class switching to produce IgE. What is the MOST likely effector function that will be enhanced by this switch?

What is the direct mechanism by which an antibody mediates neutralization?

Which factor primarily determines whether an antibody will promote inflammation or suppress it?

While studying the immune system, a researcher discovers a novel protein that, when bound to IgA, prevents its interaction with the polymeric immunoglobulin receptor (pIgR). What is the MOST likely consequence of this interaction?

Consider a scenario where a new bacterial strain has evolved a mechanism to cleave C3b into inactive fragments. What is the MOST likely immediate consequence of this bacterial adaptation within the host?

A researcher is investigating a new drug that aims to modulate class switch recombination (CSR) to enhance the production of IgG3 in response to a specific viral infection. Which cellular interaction should the drug MOST directly target to achieve this outcome?

Which antibody isotype is MOST effective at neutralizing toxins in the bloodstream, and why?

A neonate is diagnosed with a genetic defect that impairs the function of the neonatal Fc receptor, FcRn. Which immunological consequence is MOST likely to occur in this infant?

A researcher discovers that a particular antigen is able to activate the alternative pathway of complement, but is resistant to opsonization. Which modification of the antigen would MOST likely render it susceptible to opsonization?

An experimental drug is designed to completely inhibit the function of C1q. What downstream effects would result from the use of this drug?

Which of the following characteristics would render a molecule LEAST likely to be recognized as foreign by the immune system?

Which event is LEAST likely to occur as a direct result of class switch recombination (CSR)?

Which mechanism enables antibodies to prevent a pathogen from infecting cells?

If the gene encoding for AID (Activation-Induced Cytidine Deaminase) were non-functional, which process would be MOST directly impaired?

A patient with a respiratory infection is found to have high levels of IgD in their respiratory tract. This is MOST indicative which immunological process?

A novel therapeutic approach aims to enhance the recruitment of immune complexes (ICs) to erythrocytes via the CR1 receptor, but unexpectedly leads to severe systemic inflammation. Which mechanism BEST explains this paradoxical outcome?

A researcher engineers a novel immunotherapeutic fusion protein consisting of a target antigen linked to a modified Fc region that selectively binds to FcγRIIB with picomolar affinity. Contrary to expectations, in vivo administration exacerbates inflammation. What is the MOST likely reason for this outcome?

A patient presents with recurring parasitic worm infections despite producing high levels of IgE. Further investigation reveals a mutation in the gene encoding a key signaling molecule downstream of FcεRI in eosinophils. Which signaling defect would MOST likely explain this patient's susceptibility to parasitic infections?

A research team is developing a novel vaccine strategy that aims to elicit broadly neutralizing antibodies against a highly variable virus. They discover that including a specific adjuvant leads to a dramatic increase in the avidity of the resulting IgG antibodies, but also results in reduced somatic hypermutation. What is the MOST probable explanation for this observation?

A biotechnology company is designing a bispecific antibody to treat cancer. One arm binds to a tumor-associated antigen, while the other arm is designed to enhance ADCC. Which modification to the Fc region would MOST effectively augment NK cell-mediated cytotoxicity while minimizing complement activation?

A researcher is investigating the role of IgA in preventing bacterial translocation across the intestinal epithelium. They discover a novel bacterial protease that specifically cleaves IgA2 within the hinge region. What is the MOST likely consequence of IgA2 cleavage in the context of intestinal immunity?

A neonate is diagnosed with a rare genetic defect that results in the complete absence of the neonatal Fc receptor (FcRn) in all tissues except the placenta, where its expression and function are normal. What is the MOST likely immunological consequence for this infant?

A research scientist is investigating a novel strategy to enhance mucosal immunity against respiratory pathogens. They engineer a modified IgA antibody that exhibits enhanced binding to surfactant protein D (SP-D). What is the MOST likely outcome of this modification in the context of lung immunity?

A patient with a history of recurrent bacterial infections is found to have normal levels of all antibody isotypes, but their IgM exhibits a significantly reduced capacity to activate the classical complement pathway. Further investigation reveals a mutation affecting the Cµ4 domain of IgM. Which functional consequence is MOST likely associated with this mutation?

A researcher discovers a novel viral evasion mechanism involving a virally encoded protein that specifically binds to C4b, preventing its association with C2a. Which step in the classical complement pathway is MOST directly inhibited by this viral protein?

A clinician is treating a patient with a severe autoimmune disease characterized by the formation of pathogenic immune complexes. They decide to administer a high dose of intravenous immunoglobulin (IVIg) to modulate the immune response. Which Fc-mediated mechanism is MOST likely responsible for the therapeutic effect of IVIg in this context?

A researcher is studying the impact of glycosylation on the effector functions of IgG antibodies. They produce two versions of an IgG1 antibody, one with normal glycosylation and one with completely removed N-linked glycans from the Fc region. How would the removal of N-linked glycans from the Fc region of IgG1 MOST likely affect its effector functions?

A pharmaceutical company is developing a novel therapeutic antibody that targets a cytokine involved in allergic inflammation. They aim to minimize the risk of off-target effects mediated by Fc receptor interactions. Which modification to the Fc region of the antibody would BEST achieve this goal?

A researcher is investigating the mechanisms underlying the development of food allergies. They hypothesize that impaired IgA production in the gut leads to increased sensitization to food antigens. Which experimental approach would BEST test this hypothesis in a mouse model?

A patient with a history of severe asthma experiences a life-threatening exacerbation triggered by exposure to a specific allergen. Despite aggressive bronchodilator therapy, their airway inflammation persists. Which antibody-mediated mechanism is MOST likely contributing to the persistent airway inflammation in this patient?

A researcher is investigating the influence of different cytokines on class switch recombination (CSR). They stimulate B cells with anti-CD40 and IL-4, but also add a novel compound that inhibits the activity of STAT6. What is the MOST likely consequence of STAT6 inhibition on CSR in these stimulated B cells?

A researcher discovers that a particular antigen, while possessing high molecular weight and chemical complexity, fails to elicit a strong antibody response in vivo. Further analysis reveals that the antigen is rapidly degraded in the endosomes of antigen-presenting cells. Which strategy would MOST effectively enhance the immunogenicity of this antigen?

A biotech company is developing a novel therapeutic antibody to neutralize a soluble inflammatory mediator. To optimize its pharmacokinetic properties, they aim to engineer the antibody to maximize its interaction with FcRn. Which strategy would MOST effectively increase FcRn binding affinity while minimizing the risk of inducing unwanted effector functions?

A patient is diagnosed with a rare genetic deficiency in activation-induced cytidine deaminase (AID) specifically affecting somatic hypermutation in B cells, but not class switch recombination. Which downstream effect would MOST likely be observed in this individual?

A research team discovers a novel bacterial pathogen that expresses a surface protein with high affinity for polymeric immunoglobulin receptor (pIgR). What is the MOST likely functional consequence of this interaction for the host's immune response?

A researcher is investigating mechanisms of immune evasion employed by a newly discovered virus. They identify a viral protein that selectively inhibits the formation of the alternative C3 convertase (C3bBb). How would this viral protein MOST directly affect the host's immune response?

While investigating a new vaccine adjuvant, a researcher discovers it induces robust IgG responses, but the resulting antibodies exhibit unusually short half-lives in vivo. Further analysis reveals the adjuvant promotes aberrant glycosylation of the IgG Fc region. Which specific glycosylation change would MOST likely explain the reduced IgG half-life?

A patient is treated successfully for a venomous snake bite with antivenom containing neutralizing antibodies. However, several weeks later, the patient develops serum sickness, characterized by fever, joint pain, and glomerulonephritis. Which mechanism is MOST likely responsible for the development of serum sickness in this patient?

A researcher is investigating the role of Fc receptors in regulating macrophage activation. They discover that ligation of a specific Fc receptor on macrophages by IgG immune complexes triggers the production of IL-10, an immunosuppressive cytokine. Which class of Fc receptor is MOST likely mediating this effect?

A researcher aims to develop a novel therapeutic strategy for treating autoimmune hemolytic anemia, an autoantibody-mediated disease where red blood cells (RBCs) are targeted for destruction. Which approach is MOST likely to be effective in reducing RBC destruction while minimizing systemic immunosuppression?

During an investigation of a novel immune deficiency, a researcher discovers that a patient's B cells are capable of initiating class switch recombination (CSR), but unable to complete the process efficiently. Genomic analysis reveals a mutation affecting the non-homologous end joining (NHEJ) pathway specifically within B cells. Which aspect of CSR is MOST likely impaired in this patient?

A researcher is developing a vaccine against a highly glycosylated virus. The vaccine elicits a strong IgG response, but the resulting antibodies exhibit poor neutralizing activity against the native virus. Which factor is MOST likely contributing to the reduced neutralizing potency of the antibodies?

A study reveals that a particular adjuvant skews the isotype profile towards IgG2 in mice. This adjuvant causes enhanced signaling through which receptor on B cells?

A newborn has significantly reduced levels of IgG but normal levels of IgM and IgA. Which condition would MOST likely explain this observation?

A novel drug is designed to enhance the presentation of antigens on MHC class II molecules by B cells. The drug MOST likely targets what aspect of B cell function?

A research team discovers a novel immunodeficiency characterized by impaired somatic hypermutation and class switch recombination, but with normal germinal center formation. Comprehensive analysis reveals a specific defect in the glycosylation pathway within B cells, leading to the production of aberrant N-glycans on the activation-induced cytidine deaminase (AID) enzyme. Which consequence is MOST likely resulting from the altered glycosylation of AID?

A hypothetical biopharmaceutical company is engineering a novel, multi-specific antibody construct. One arm binds to a tumor-specific antigen, while a second arm is designed to directly activate the alternative pathway of complement. To optimize the therapeutic efficacy while minimizing systemic inflammatory side effects, which of these design considerations is MOST critical?

A research team aims to develop a novel vaccine against a highly variable viral pathogen. They engineer a virus-like particle (VLP) displaying conserved viral epitopes and administer it with different adjuvants. Unexpectedly, they observe that an adjuvant known to potently activate dendritic cells leads to significantly lower avidity of the resulting IgG antibodies compared to an adjuvant that induces weaker DC activation. Which mechanism is the MOST probable explanation for this observation?

A research group is investigating the role of different IgA subclasses in maintaining intestinal homeostasis. They discover a novel commensal bacterial species that secretes a highly specific protease that cleaves IgA1, but not IgA2, within the hinge region. What is the MOST likely long-term consequence of this proteolytic activity on the host's intestinal immunity?

A researcher is studying the impact of passive immunization on the development of autoimmune disease in a mouse model. They transfer IgG antibodies specific for a self-antigen known to drive disease pathogenesis. Surprisingly, they observe a transient amelioration of disease followed by a significant disease exacerbation. Which Fc-mediated mechanism is MOST likely responsible for the observed disease exacerbation?