A 38-year-old woman presents with cyclic pelvic pain, dysmenorrhea, and dyspareunia. On pelvic examination, the uterus is retroverted and fixed. Which of the following conditions is most likely to be responsible for these findings?

Correct Answer: A

Rationale: Endometriosis is the most likely condition responsible for the symptoms described in this scenario. Endometriosis is a chronic condition in which endometrial-like tissue grows outside the uterus, commonly affecting the pelvic structures such as the ovaries, fallopian tubes, and pelvic peritoneum. The main symptoms include cyclic pelvic pain, dysmenorrhea (painful periods), and dyspareunia (pain during intercourse). The retroverted and fixed uterus on examination may be due to adhesions from endometriosis, causing the uterus to be fixed in position. Endometriosis should be considered in women of reproductive age presenting with these symptoms and pelvic examination findings.

Correct Answer: A

Rationale: Immunological memory is primarily maintained by the clonal expansion of memory B cells. Memory B cells are a type of long-lived immune cell that originates from previously activated B cells during an immune response to a pathogen. When the immune system encounters the same pathogen again, memory B cells can quickly recognize and respond to it by undergoing rapid clonal expansion and differentiation into plasma cells that produce specific antibodies. This quick and robust response leads to the more efficient elimination of the pathogen during secondary exposure, resulting in the faster and stronger immune response characteristic of immunological memory.

Correct Answer: A

Rationale: A patient with a severe viral infection exhibiting reduced levels of circulating lymphocytes is likely due to the apoptosis of infected lymphocytes. When a virus enters the body, it can infect and replicate within lymphocytes, subsequently triggering the immune system to induce apoptosis in infected cells to prevent further spread of the virus. This process is part of the body's defense mechanism to control the viral infection. As a result, the circulating lymphocyte levels may decrease as infected lymphocytes are targeted for apoptosis. This phenomenon helps to limit viral replication and spread within the body, thereby aiding in the immune response to eliminate the virus.

Correct Answer: A

Rationale: Opsonization refers to the process by which antibodies bind to the surface of pathogens, marking them for destruction by phagocytes or complement proteins. This coating of antibodies enhances the ability of the immune system to recognize and eliminate the pathogens effectively. Phagocytes (such as macrophages and neutrophils) are better able to engulf and digest pathogens that have been opsonized, as the antibodies attached to the pathogen surface signal to the phagocytes that they are foreign invaders. This process is crucial in the body's immune response to infections and helps in clearing pathogens from the system.

Correct Answer: C

Rationale: In a patient with ARDS who is experiencing refractory hypoxemia despite maximal ventilatory support and prone positioning, the use of extracorporeal membrane oxygenation (ECMO) is a potentially life-saving adjunctive therapy. ECMO works by providing temporary support for gas exchange outside the body, allowing the lungs to rest and heal while providing adequate oxygenation and carbon dioxide removal. The use of ECMO has been associated with improved oxygenation and reduced mortality in severe cases of ARDS, especially in patients who fail conventional therapies. High-frequency oscillatory ventilation (HFOV) has not consistently shown mortality benefit in ARDS, continuous renal replacement therapy (CRRT) is not directly indicated for hypoxemia in ARDS, and inhaled nitric oxide (iNO) has shown limited benefit in improving oxygenation in ARDS without a clear impact on mortality.