Questions & explanations
1. Compare costimulation blockade with standard calcineurin inhibitors for preventing rejection.
Standard calcineurin inhibitors like tacrolimus block a key signal inside T cells, stopping their activation broadly. This is effective but can damage kidneys and cause high blood pressure. Costimulation blockade more specifically targets the second signal, so it may cause less kidney damage. However, costimulation blockade is weaker at preventing acute rejection in the first few months. It also increases risk of a type of viral infection called post-transplant lymphoproliferative disorder. Many transplant centers use a combination: costimulation blockade with lower doses of other drugs. Overall, costimulation blockade offers a kidney-friendly option but requires careful patient selection.
2. Compare the risk of autoimmunity after COVID-19 with the risk after vaccination.
The risk of autoimmunity after COVID-19 infection is higher than after vaccination. Infection causes widespread inflammation and viral replication, which can trigger autoimmunity through mimicry and bystander activation. Vaccination uses a harmless piece of the virus (like the spike protein) to train the immune system, so it does not cause full-blown infection. Rare cases of autoimmune reactions after vaccination have been reported, but they are much less common than after natural infection. For example, Guillain-Barré syndrome is more frequent after COVID-19 than after the vaccine. Overall, vaccination is safer and reduces the risk of severe disease and its autoimmune complications.
3. Compare the clinical features of immune complex disease due to complement deficiency versus that due to other causes (like infection).
Immune complex disease from complement deficiency often starts early in life and includes recurrent infections and autoimmune symptoms like lupus. For example, a child with C4 deficiency may have frequent bacterial infections and develop a lupus-like rash. In contrast, immune complex disease from infection (like post-streptococcal glomerulonephritis) occurs after a specific infection and usually resolves. The deficiency-related disease is chronic and may require lifelong management. Also, deficiency-related disease often involves multiple family members, while infection-related is sporadic. Treatment differs: deficiency may need complement replacement or infection prophylaxis.
4. Compare the risk of developing autoimmune disease from the COVID-19 vaccine versus the COVID-19 infection.
The risk of developing autoimmune disease from the COVID-19 vaccine is extremely low, while the risk from COVID-19 infection is higher. Studies show that COVID-19 infection can trigger conditions like Guillain-Barré syndrome, lupus, and rheumatoid arthritis in some people. In contrast, the COVID-19 vaccines have been associated with very rare cases of myocarditis (heart inflammation) and Guillain-Barré syndrome, but at rates much lower than after infection. For example, myocarditis after mRNA vaccines is about 1 in 10,000 young males, but after COVID-19, it is more common. Overall, vaccination reduces the overall risk of autoimmune complications by preventing severe disease.
5. Compare Treg therapy and tolerogenic DC therapy for inducing transplant tolerance.
Both therapies aim to create a tolerant immune system, but they work differently. Tregs directly suppress other immune cells, while tolerogenic DCs educate T cells to become tolerant. Treg therapy provides a ready-made army of suppressors, but they may not survive long. Tolerogenic DCs can induce long-lasting tolerance by training the immune system, but the effect takes time. Manufacturing Tregs requires sorting pure cells, which is complex; tolerogenic DCs are easier to produce from monocytes. Both therapies are being tested in clinical trials, often combined with low-dose drugs. The best approach may depend on the patient's immune status and organ type.
6. Compare the immunological barriers in xenotransplantation versus allotransplantation.
Xenotransplantation faces additional barriers beyond allotransplantation. In allotransplantation, rejection is mediated by T cells and antibodies against HLA. In xenotransplantation, there are pre-existing antibodies against non-HLA antigens (like alpha-gal) causing hyperacute rejection. Also, molecular incompatibilities in complement regulation and coagulation lead to thrombotic microangiopathy. The cellular immune response is stronger due to many foreign proteins. Chronic rejection in xenografts involves both antibody and cellular mechanisms. Thus, xenotransplantation requires more extensive genetic engineering and immunosuppression.
7. How does the error-prone repair during somatic hypermutation lead to antibody diversity?
After AID deaminates cytosines to uracils, the uracils are recognized by uracil DNA glycosylase (UNG) or mismatch repair proteins. UNG removes uracil, creating an abasic site that is replicated by error-prone DNA polymerases (e.g., Pol η, Pol ζ). These polymerases often insert incorrect bases, leading to mutations. Mismatch repair also introduces mutations by recruiting error-prone polymerases during gap filling. The mutations are concentrated in the complementarity-determining regions (CDRs) because of the local DNA sequence and transcription. This generates a diverse pool of antibodies, from which high-affinity clones are selected.
8. How can you tell Hashimoto's disease apart from Graves' disease?
Hashimoto's disease usually causes hypothyroidism, with symptoms like fatigue, weight gain, feeling cold, and constipation. Graves' disease causes hyperthyroidism, with symptoms like weight loss, rapid heartbeat, heat intolerance, and bulging eyes (exophthalmos). Blood tests show opposite hormone levels: low T4 and high TSH in Hashimoto's, high T4 and low TSH in Graves'. Antibodies also differ: anti-thyroid peroxidase (TPO) in Hashimoto's, and thyroid-stimulating immunoglobulin (TSI) in Graves'. Treatment differs: Hashimoto's needs thyroid hormone replacement, while Graves' may use anti-thyroid drugs, radioactive iodine, or surgery.
9. What is the main job of the IL-10 family of cytokines in the immune system?
The IL-10 family of cytokines, which includes IL-10, IL-19, IL-20, IL-22, IL-24, and IL-26, mainly helps control inflammation and keeps the immune system from overreacting. IL-10 itself is a strong anti-inflammatory cytokine that stops immune cells like macrophages and T cells from making too many inflammatory signals. Other family members, like IL-22, help protect and repair tissues like the skin and gut. For example, during an infection, IL-10 limits damage by reducing inflammation after the pathogen is cleared. This family is important for keeping a balance between fighting germs and avoiding harm to the body's own tissues.
10. What is the goal of desensitization protocols for HLA-sensitized patients?
Desensitization protocols aim to reduce the level of anti-HLA antibodies in a patient's blood before transplantation. This allows a sensitized patient, who would otherwise be at high risk of rejection, to receive a kidney or other organ from a donor with incompatible HLA. The main approaches include plasmapheresis, which filters antibodies from the blood, and intravenous immunoglobulin (IVIG), which neutralizes antibodies and modulates the immune system. These treatments can lower antibody levels enough to permit successful transplantation. However, desensitization is not always effective and carries risks such as infection.
11. Compare the immunological challenges in liver transplantation versus kidney transplantation.
Kidney transplants face a higher risk of acute rejection, especially antibody-mediated rejection, because the kidney is more susceptible to antibody damage. Liver transplants have a lower incidence of hyperacute rejection and can sometimes tolerate HLA mismatches. The liver can absorb donor-specific antibodies, protecting itself. However, liver recipients may experience chronic rejection (vanishing bile duct syndrome) that is harder to treat. Kidney recipients often require lifelong immunosuppression, while some liver recipients can achieve operational tolerance (stable graft without drugs). Both require careful monitoring.
12. Compare pre-existing DSA and de novo DSA in terms of risk and management.
Pre-existing DSA are present before transplant, often due to previous transplants, blood transfusions, or pregnancies. They pose a high risk of early rejection. Management includes desensitization before transplant and stronger drugs after. De novo DSA develop after transplant, usually due to poor drug adherence or inadequate immunosuppression. They often appear later and can cause chronic rejection. Management involves improving drug levels and adding treatments like IVIG. Both types require close monitoring, but pre-existing DSA need more aggressive upfront treatment. De novo DSA may be easier to reverse if caught early.