Pancreas and islet cell transplantation US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Pancreas and islet cell transplantation. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Pancreas and islet cell transplantation US Medical PG Question 1: A 48-year-old Caucasian male suffering from ischemic heart disease is placed on a heart transplant list. Months later, he receives a heart from a matched donor. During an endomyocardial biopsy performed 3 weeks later, there is damage consistent with acute graft rejection. What is most likely evident on the endomyocardial biopsy?
- A. Granuloma
- B. Atherosclerosis
- C. Lymphocytic infiltrate (Correct Answer)
- D. Tissue necrosis
- E. Fibrosis
Pancreas and islet cell transplantation Explanation: ***Lymphocytic infiltrate***
- Acute graft rejection, especially within weeks of transplantation, is characterized by a **cellular immune response** dominated by **T lymphocytes** invading the allograft.
- These lymphocytes target donor major histocompatibility complex (MHC) molecules, leading to myocyte damage and dysfunction, which would be visible as a lymphocytic infiltrate on biopsy.
*Granuloma*
- Granulomas are aggregates of **macrophages**, often seen in chronic inflammatory conditions like tuberculosis, sarcoidosis, or fungal infections.
- They are not typical findings in the context of acute allograft rejection.
*Atherosclerosis*
- Atherosclerosis is a disease of large and medium-sized arteries characterized by **plaque formation**, primarily involving lipid deposition and inflammation, which narrows the arterial lumen.
- While it can affect transplanted organs (e.g., transplant vasculopathy, a form of chronic rejection), it is not the primary mechanism or histological finding in **acute cellular rejection** occurring three weeks post-transplant.
*Tissue necrosis*
- While acute rejection can *lead* to tissue necrosis due to severe inflammation and ischemia, necrosis alone is a broad term and not the most specific or defining histological feature of acute cellular rejection.
- The preceding and primary histopathological hallmark of acute cellular rejection is the **inflammatory cell infiltrate**, particularly lymphocytes attacking the graft.
*Fibrosis*
- Fibrosis, or the deposition of excess connective tissue, is a characteristic feature of **chronic rejection** or chronic injury processes.
- It indicates long-standing damage and repair, which is unlikely to be the predominant finding in a biopsy three weeks after transplantation indicative of acute rejection.
Pancreas and islet cell transplantation US Medical PG Question 2: A 40-year-old male with a history of chronic alcoholism recently received a liver transplant. Two weeks following the transplant, the patient presents with a skin rash and frequent episodes of bloody diarrhea. A colonoscopy is performed and biopsy reveals apoptosis of colonic epithelial cells. What is most likely mediating these symptoms?
- A. Donor T-cells (Correct Answer)
- B. Recipient T-cells
- C. Recipient B-cells
- D. Recipient antibodies
- E. Donor B-cells
Pancreas and islet cell transplantation Explanation: ***Donor T-cells***
- This clinical presentation of **skin rash**, **bloody diarrhea**, and **colonic epithelial apoptosis** following an allogeneic transplant (like a liver transplant) is classic for **Graft-versus-Host Disease (GVHD)**.
- In GVHD, **immunocompetent T-cells from the donor** recognize the recipient's tissues as foreign and mount an immune attack, causing damage to organs like the skin, gastrointestinal tract, and liver.
*Recipient T-cells*
- **Recipient T-cells** are typically immunosuppressed following an organ transplant to prevent organ rejection.
- Furthermore, if activated, recipient T-cells would target the donor organ (the liver in this case), leading to **rejection**, rather than the systemic symptoms observed (skin rash, bloody diarrhea) which suggest an attack by donor cells on recipient tissues.
*Recipient B-cells*
- While recipient B-cells can be involved in **antibody-mediated rejection** of the transplanted organ, they are not the primary mediators of **cellular GVHD**.
- **Antibody-mediated rejection** would typically involve antibodies targeting the donor liver, leading to liver dysfunction, not the widespread GVHD symptoms described.
*Recipient antibodies*
- **Recipient antibodies** are primarily involved in **antibody-mediated rejection** of the transplanted organ, which would manifest as dysfunction of the transplanted liver.
- They do not mediate the symptoms of **Graft-versus-Host Disease (GVHD)**, which is a cell-mediated immune response.
*Donor B-cells*
- **Donor B-cells** are generally not the primary mediators of GVHD.
- While donor immune cells are crucial for GVHD, the major players are **donor T-cells**, which directly recognize and attack host tissues.
Pancreas and islet cell transplantation US Medical PG Question 3: A 45-year-old woman comes to the physician because of a 3-month history of worsening fatigue, loss of appetite, itching of the skin, and progressive leg swelling. Although she has been drinking 2–3 L of water daily, she has been passing only small amounts of urine. She has type 1 diabetes mellitus, chronic kidney disease, hypertension, and diabetic polyneuropathy. Her current medications include insulin, torasemide, lisinopril, and synthetic erythropoietin. Her temperature is 36.7°C (98°F), pulse is 87/min, and blood pressure is 138/89 mm Hg. She appears pale. There is 2+ pitting edema in the lower extremities. Sensation to pinprick and light touch is decreased over the feet and legs bilaterally. Laboratory studies show:
Hemoglobin 11.4 g/dL
Leukocyte count 6000/mm3
Platelet count 280,000/mm3
Serum
Na+ 137 mEq/L
K+ 5.3 mEq/L
Cl− 100 mEq/L
HCO3− 20 mEq/L
Urea nitrogen 85 mg/dL
Creatinine 8 mg/dL
pH 7.25
Which of the following long-term treatments would best improve quality of life and maximize survival in this patient?
- A. Peritoneal dialysis
- B. Living donor kidney transplant (Correct Answer)
- C. Cadaveric kidney transplant
- D. Hemofiltration
- E. Fluid restriction
Pancreas and islet cell transplantation Explanation: ***Living donor kidney transplant***
- A **living donor kidney transplant** offers the best outcomes for **quality of life and survival** in eligible patients with end-stage renal disease (ESRD), particularly when compared to dialysis, due to better graft survival rates and reduced complications.
- The patient's symptoms (fatigue, itching, leg swelling, oliguria, high urea nitrogen, creatinine, hyperkalemia, metabolic acidosis) are consistent with **ESRD**, and while she has several comorbidities, she is not explicitly stated to have contraindications for transplantation.
*Peritoneal dialysis*
- While an effective treatment for ESRD, **dialysis generally provides lower quality of life** and survival benefits compared to successful kidney transplantation.
- She already has significant fluid overload symptoms and **oliguria**, making adequate fluid removal through peritoneal dialysis potentially challenging without strict management and impacting her overall well-being.
*Cadaveric kidney transplant*
- A **cadaveric kidney transplant** is a viable option and offers better outcomes than dialysis, but it generally has **poorer graft survival** and a longer wait time compared to a living donor transplant due to delayed graft function and cold ischemia time.
- Given the option, a **living donor transplant is superior** in terms of long-term outcomes and reduces the time spent on dialysis.
*Hemofiltration*
- **Hemofiltration is a form of renal replacement therapy**, similar to hemodialysis, often used in acute settings or for critically ill patients with severe fluid overload or electrolyte imbalances.
- While it can manage her symptoms, it is not a long-term treatment that **improves quality of life or maximizes survival** better than transplantation for ESRD.
*Fluid restriction*
- **Fluid restriction** is a supportive measure to manage fluid overload in patients with ESRD; however, it addresses symptoms rather than the underlying progressive renal failure.
- While necessary as part of supportive care, it does not offer a definitive long-term solution or improve survival for ESRD, which requires **renal replacement therapy or transplantation**.
Pancreas and islet cell transplantation US Medical PG Question 4: Twelve days after undergoing a cadaveric renal transplant for adult polycystic kidney disease, a 23-year-old man has pain in the right lower abdomen and generalized fatigue. During the past 4 days, he has had decreasing urinary output. Creatinine concentration was 2.3 mg/dL on the second postoperative day. Current medications include prednisone, cyclosporine, azathioprine, and enalapril. His temperature is 38°C (100.4°F), pulse is 103/min, and blood pressure is 168/98 mm Hg. Examination reveals tenderness to palpation on the graft site. Creatinine concentration is 4.3 mg/dL. A biopsy of the transplanted kidney shows tubulitis. C4d staining is negative. Which of the following is the most likely cause of this patient's findings?
- A. Drug-induced nephrotoxicity
- B. Allorecognition with T cell activation (Correct Answer)
- C. Irreversible fibrosis of the glomerular vessels
- D. Donor T cells from the graft
- E. Preformed cytotoxic antibodies against class I HLA
Pancreas and islet cell transplantation Explanation: ***Allorecognition with T cell activation***
- The patient's symptoms (pain at graft site, fatigue, decreasing urinary output, elevated creatinine) 12 days post-transplant, along with **tubulitis on biopsy** and negative **C4d staining**, are indicative of acute cellular rejection, mediated primarily by **T-cell recognition of donor HLA antigens**.
- **Hypertension** and **fever** also support acute rejection, and the immunosuppressive regimen may not be fully effective in preventing this T-cell mediated response.
*Drug-induced nephrotoxicity*
- While cyclosporine and enalapril can cause kidney injury, the **histological finding of tubulitis** is highly specific for acute cellular rejection, not typically seen with drug-induced nephrotoxicity alone.
- Drug-induced nephrotoxicity usually presents with a more **gradual rise in creatinine** and may lack the systemic signs like fever or the specific pathological features of rejection.
*Irreversible fibrosis of the glomerular vessels*
- This description is more consistent with **chronic allograft nephropathy** or long-term damage, which typically develops months to years after transplantation, not within 12 days.
- The findings described (pain, fever, tubulitis) point to an acute process, not chronic fibrosis.
*Donor T cells from the graft*
- This scenario describes **graft-versus-host disease (GVHD)**, which is rare in solid organ transplantation due to the much smaller lymphocyte load compared to bone marrow transplants.
- GVHD typically affects the skin, liver, and gut, and while it involves T-cell mediated injury, the primary damage in renal transplant rejection is directed at the transplanted kidney by the recipient's immune system.
*Preformed cytotoxic antibodies against class I HLA*
- This describes **hyperacute rejection**, which occurs within minutes to hours of transplantation due to pre-existing antibodies in the recipient against donor antigens.
- The patient's symptoms developing 12 days post-transplant, along with the biopsy showing tubulitis and negative C4d staining (indicating absence of significant antibody-mediated complement activation), rule out hyperacute rejection.
Pancreas and islet cell transplantation US Medical PG Question 5: A researcher is tracing the fate of C-peptide, a product of preproinsulin cleavage. Which of the following is a true statement regarding the fate of C-peptide?
- A. C-peptide exits the cells via a protein channel
- B. C-peptide is further cleaved into insulin
- C. C-peptide is packaged with insulin in secretory vesicles (Correct Answer)
- D. C-peptide is immediately degraded by the proteasome
- E. C-peptide activates an intracellular signaling cascade
Pancreas and islet cell transplantation Explanation: ***C-peptide is packaged with insulin in secretory vesicles***
- Preproinsulin is cleaved in the **endoplasmic reticulum** to proinsulin (signal peptide removal), which is then transported to the **Golgi apparatus**.
- In the Golgi, proinsulin is cleaved by **prohormone convertases** into **insulin** and **C-peptide**, and both are stored together in **secretory vesicles** within the pancreatic beta cells.
- Upon stimulation, both insulin and C-peptide are **co-secreted** via exocytosis in equimolar amounts, making C-peptide a useful marker of endogenous insulin secretion.
*C-peptide exits the cells via a protein channel*
- C-peptide exits the beta cells via **exocytosis** of secretory granules, not through specific protein channels.
- It is **co-secreted with insulin** when secretory vesicles fuse with the plasma membrane.
- Its presence in the bloodstream in equimolar amounts with insulin makes it an indirect measure of **insulin secretion**.
*C-peptide is further cleaved into insulin*
- **C-peptide** is a product of proinsulin cleavage, alongside insulin; it is not further processed into insulin.
- Insulin itself is composed of two **peptide chains (A and B)** linked by disulfide bonds, formed after C-peptide is removed from proinsulin.
*C-peptide is immediately degraded by the proteasome*
- C-peptide is not immediately degraded by the **proteasome** upon synthesis.
- After secretion, it circulates in the blood with a **longer half-life** than insulin (approximately 30 minutes versus 4-6 minutes), allowing it to be a useful marker of endogenous insulin production.
- Its degradation occurs primarily in the **kidney**.
*C-peptide activates an intracellular signaling cascade*
- While there is some research suggesting C-peptide may have independent **biological activity** and activate certain signaling pathways extracellularly, its primary role in the context of the insulin synthesis pathway is as a **byproduct** of proinsulin processing.
- Its clinical utility is primarily as a **biomarker** of endogenous insulin secretion, particularly useful in distinguishing between endogenous and exogenous insulin in diabetic patients.
Pancreas and islet cell transplantation US Medical PG Question 6: A 13-year-old girl presents after losing consciousness during class 30 minutes ago. According to her friends, she was doing okay since morning, and nobody noticed anything abnormal. The patient’s mother says that her daughter does not have any medical conditions. She also says that the patient has always been healthy but has recently lost weight even though she was eating as usual. Her vital signs are a blood pressure of 100/78 mm Hg, a pulse of 89/min, and a temperature of 37.2°C (99.0°F). Her breathing is rapid but shallow. Fingerstick glucose is 300 mg/dL. Blood is drawn for additional lab tests, and she is started on intravenous insulin and normal saline. Which of the following HLA subtypes is associated with this patient’s most likely diagnosis?
- A. DR3 (Correct Answer)
- B. A3
- C. B8
- D. DR5
- E. B27
Pancreas and islet cell transplantation Explanation: ***DR3***
- The patient's presentation with **recent weight loss despite normal eating**, rapid but shallow breathing (**Kussmaul respiration** hinting at **metabolic acidosis**), elevated blood glucose (300 mg/dL), and loss of consciousness strongly suggests **Type 1 Diabetes Mellitus (T1DM)** presenting as **diabetic ketoacidosis (DKA)**.
- **HLA-DR3** and **HLA-DR4** are the primary genetic markers most strongly associated with an increased susceptibility to Type 1 Diabetes Mellitus, an **autoimmune disease** affecting pancreatic beta cells.
- **HLA-DR3** is the most direct answer as it is one of the two strongest HLA-DR associations with T1DM.
*A3*
- **HLA-A3** is primarily associated with **hemochromatosis**, a disorder of iron metabolism, and is not a common genetic marker for Type 1 Diabetes Mellitus.
- The symptoms described in the patient (weight loss, hyperglycemia, DKA) are not characteristic of hemochromatosis.
*B8*
- **HLA-B8** is actually associated with Type 1 Diabetes Mellitus as part of the **extended haplotype A1-B8-DR3**, which shows strong linkage disequilibrium.
- However, **HLA-B8 is not as directly or specifically associated with T1DM** as the HLA-DR subtypes (DR3 and DR4), which are considered the primary genetic markers.
- When asking about HLA subtypes associated with T1DM, **DR3 or DR4** are the best answers as they show the strongest and most direct association.
- HLA-B8 is also associated with other autoimmune conditions like **myasthenia gravis** and **Graves' disease**.
*DR5*
- While part of the **HLA-DR family**, **HLA-DR5** is less commonly associated with **Type 1 Diabetes Mellitus** compared to DR3 and DR4.
- This subtype is more frequently linked with conditions like **pernicious anemia** or increased risk of certain infections.
*B27*
- **HLA-B27** is strongly associated with **seronegative spondyloarthropathies**, such as **ankylosing spondylitis** and **reactive arthritis**.
- It has no known direct association with **Type 1 Diabetes Mellitus**.
Pancreas and islet cell transplantation US Medical PG Question 7: A 49-year-old man comes to the emergency department because of recurrent abdominal pain for 1 week. The pain is worse after eating and he has vomited twice during this period. He was hospitalized twice for acute pancreatitis during the past year; the latest being 2 months ago. There is no family history of serious illness. His only medication is a vitamin supplement. He has a history of drinking five beers a day for several years but quit 1 month ago. His temperature is 37.1°C (98.8°F), pulse is 98/min and blood pressure 110/70 mm Hg. He appears uncomfortable. Examination shows epigastric tenderness to palpation; there is no guarding or rebound. A CT scan of the abdomen shows a 6-cm low attenuation oval collection with a well-defined wall contiguous with the body of the pancreas. Which of the following is the most appropriate next step in management?
- A. Magnetic resonance cholangiopancreatography
- B. CT-guided percutaneous drainage (Correct Answer)
- C. Middle segment pancreatectomy
- D. Laparoscopic surgical drainage
- E. Distal pancreatectomy
Pancreas and islet cell transplantation Explanation: ***CT-guided percutaneous drainage***
- The patient presents with a **symptomatic pancreatic pseudocyst** (recurrent abdominal pain, vomiting, epigastric tenderness) that is 6 cm and has a well-defined wall.
- Given the patient's symptoms and the size/maturity of the pseudocyst, **CT-guided percutaneous drainage** is the most appropriate initial management to relieve symptoms and drain the fluid.
*Magnetic resonance cholangiopancreatography*
- **MRCP** is primarily used to visualize the **biliary and pancreatic ductal systems**, often to identify stones, strictures, or anatomical variations.
- While it can provide more detailed imaging of the pancreatic ducts, it is not a treatment for a symptomatic pseudocyst and would not relieve the patient's immediate pain and vomiting.
*Middle segment pancreatectomy*
- **Pancreatectomies** are **surgical resections** of part or all of the pancreas, typically reserved for tumors, severe necrosis, or intractable pain from chronic pancreatitis not amenable to less invasive treatments.
- This is an **overly aggressive surgical intervention** for a pseudocyst that can likely be managed with drainage.
*Laparoscopic surgical drainage*
- **Laparoscopic internal drainage** (e.g., cystogastrostomy) is an option for mature, symptomatic pseudocysts, but it is typically performed after a period of observation and if percutaneous drainage is unsuccessful or not feasible.
- Percutaneous drainage is generally preferred as the **initial less invasive approach** for managing symptomatic pseudocysts.
*Distal pancreatectomy*
- **Distal pancreatectomy** involves the surgical removal of the body and tail of the pancreas and is indicated for conditions such as tumors localized in these regions or for specific cases of chronic pancreatitis.
- It is an **aggressive surgical procedure** and not the first-line treatment for a symptomatic pancreatic pseudocyst, especially if less invasive options are available.
Pancreas and islet cell transplantation US Medical PG Question 8: A 57-year-old woman comes to the clinic complaining of decreased urine output. She reports that over the past 2 weeks she has been urinating less and less every day. She denies changes in her diet or fluid intake. The patient has a history of lupus nephritis, which has resulted in end stage renal disease. She underwent a renal transplant 2 months ago. Since then she has been on mycophenolate and cyclosporine, which she takes as prescribed. The patient’s temperature is 99°F (37.2°C), blood pressure is 172/102 mmHg, pulse is 88/min, and respirations are 17/min with an oxygen saturation of 97% on room air. Labs show an elevation in serum creatinine and blood urea nitrogen. On physical examination, she has 2+ pitting edema of the bilateral lower extremities. Lungs are clear to auscultation. Urinalysis shows elevated protein. A post-void bladder scan is normal. A renal biopsy is obtained, which shows lymphocyte infiltration and intimal swelling. Which of the following is the next best step in management?
- A. Add diltiazem
- B. Nephrectomy
- C. Start intravenous steroids (Correct Answer)
- D. Add ceftriaxone
- E. Discontinue cyclosporine
Pancreas and islet cell transplantation Explanation: ***Start intravenous steroids***
- The patient presents with **decreased urine output**, elevated creatinine, and a recent kidney transplant with biopsy showing **lymphocyte infiltration** and **intimal swelling**, all highly suggestive of **acute cellular rejection**.
- **High-dose intravenous steroids** (e.g., methylprednisolone) are the first-line treatment for acute cellular rejection to suppress the immune response and preserve graft function.
*Add diltiazem*
- **Diltiazem** is a calcium channel blocker used to treat hypertension and arrhythmias, and it can also interfere with cyclosporine metabolism, potentially increasing its levels.
- While the patient has elevated blood pressure, adding diltiazem would not address the underlying **immune rejection** and would not be the primary intervention.
*Nephrectomy*
- **Nephrectomy** involves surgical removal of the transplanted kidney. This radical intervention is reserved for **irreversible graft failure** or severe complications like overwhelming infection or malignancy.
- Given the acute presentation and possibility of reversing rejection with immunosuppression, nephrectomy is **premature** and not the next best step.
*Add ceftriaxone*
- **Ceftriaxone** is an antibiotic used to treat bacterial infections.
- There is no clinical evidence in the stem (e.g., fever, signs of infection) to suggest a **bacterial infection** as the cause of her symptoms, making antibiotics inappropriate.
*Discontinue cyclosporine*
- **Cyclosporine** is an immunosuppressant essential for preventing transplant rejection. Discontinuing it would immediately increase the risk of more severe and potentially **irreversible rejection**.
- While cyclosporine can cause nephrotoxicity, the biopsy findings of **cellular infiltration** point more towards rejection rather than primary drug toxicity, and the primary treatment for rejection involves increasing immunosuppression, not withdrawing it.
Pancreas and islet cell transplantation US Medical PG Question 9: A 47-year-old woman presents to her primary care physician because of pain on urination, urinary urgency, and urinary frequency for 4 days. This is the third time for her to have these symptoms over the past 7 months. She was recently treated for candidal intertrigo. Vital signs reveal a temperature of 36.7°C (98.0°F), blood pressure of 110/70 mm Hg and pulse of 75/min. Physical examination is unremarkable except for morbid obesity. Her father has type 2 diabetes complicated by end-stage chronic kidney disease. A1C is found to be 8.5%. The patient is given a prescription for her urinary symptoms. Which of the following is the best next step for this patient?
- A. Sulphonylurea added to metformin
- B. Bariatric surgery
- C. Repeating the A1c test
- D. Basal-bolus insulin
- E. Metformin (Correct Answer)
Pancreas and islet cell transplantation Explanation: ***Metformin***
- The patient has symptoms suggestive of **uncontrolled type 2 diabetes**, including recurrent infections (urinary, intertrigo) and a familial history, despite an A1C of 8.5%.
- **Metformin** is typically the first-line pharmacologic treatment for type 2 diabetes unless contraindicated, as it improves insulin sensitivity and reduces hepatic glucose production.
*Sulphonylurea added to metformin*
- While adding a sulfonylurea to metformin is an option for patients not reaching glycemic targets on metformin alone, **monotherapy with metformin** is the initial step for newly diagnosed or uncontrolled diabetes.
- Sulfonylureas carry a higher risk of **hypoglycemia** compared to metformin and are generally added if metformin monotherapy is insufficient.
*Bariatric surgery*
- Bariatric surgery is a treatment option for **morbidly obese** individuals with type 2 diabetes, but it is typically considered after lifestyle modifications and pharmacotherapy have been attempted or when the BMI is very high (e.g., >40 or >35 with comorbidities).
- It is not the immediate next step for managing newly diagnosed or uncontrolled diabetes, especially when first-line medications haven't been initiated.
*Repeating the A1c test*
- The elevated **A1C of 8.5%**, combined with classic symptoms of hyperglycemia (recurrent infections, polyuria from urinary symptoms), is sufficient for a diagnosis of diabetes.
- Repeating the test immediately is unlikely to change the diagnosis and would delay necessary treatment initiation.
*Basal-bolus insulin*
- Basal-bolus insulin regimens are typically reserved for patients with very **high A1C levels** (e.g., >10%), significant symptoms of hyperglycemia, or those who have failed multiple oral hypoglycemic agents.
- Given an A1C of 8.5%, initiating insulin is usually not the first pharmacologic step; metformin monotherapy is preferred.
Pancreas and islet cell transplantation US Medical PG Question 10: A 24-year-old male with cystic fibrosis is brought to the emergency room by his mother after he had difficulty breathing. He previously received a lung transplant 6 months ago and was able to recover quickly from the operation. He is compliant with all of his medications and had been doing well with no major complaints until 2 weeks ago when he began to experience shortness of breath. Exam reveals a decreased FEV1/FVC ratio and biopsy reveals lymphocytic infiltration. Which of the following components is present in the airway zone characteristically affected by the most likely cause of this patient's symptoms?
- A. Pseudostratified columnar cells
- B. Goblet cells
- C. Simple cuboidal cells (Correct Answer)
- D. Stratified cuboidal cells
- E. Cartilage
Pancreas and islet cell transplantation Explanation: ***Simple cuboidal cells***
- The patient's symptoms, history of a lung transplant, and biopsy findings of **lymphocytic infiltration** suggest **bronchiolitis obliterans**, a form of chronic lung allograft dysfunction.
- Bronchiolitis obliterans primarily affects the **small airways** (bronchioles), which are characterized by an epithelial lining of **simple cuboidal cells** and lack cartilage.
*Pseudostratified columnar cells*
- These cells line the **trachea** and **main bronchi** (larger airways), which are typically not the primary site of damage in bronchiolitis obliterans.
- They are part of the **mucociliary escalator** and are also associated with cartilage.
*Goblet cells*
- While present in the **larger airways** along with pseudostratified columnar cells, goblet cells are less prominent or absent in the small bronchioles primarily affected by bronchiolitis obliterans.
- Their characteristic function is mucus production, not the specific epithelial type of the affected bronchioles.
*Stratified cuboidal cells*
- This cell type is **rare** in the respiratory tract and is not characteristic of the small airways affected by bronchiolitis obliterans.
- Stratified epithelia are typically seen in ducts of glands or specialized transitional zones, not the functional bronchioles.
*Cartilage*
- Cartilage provides structural support to the **trachea and main bronchi**, but it is **absent** in the small airways (bronchioles) that are the primary target of bronchiolitis obliterans.
- The presence of cartilage would indicate a larger airway, contradicting the pathophysiology of this condition.
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