Which of the following cell types is primarily responsible for the production of antibodies during the humoral immune response?

Correct Answer: A

Rationale: Plasma cells are the primary type of cells responsible for the production of antibodies during the humoral immune response. When activated by antigens, B cells differentiate into plasma cells, which are specialized in producing large quantities of antibodies. These antibodies are essential in fighting off infections by binding to antigens and marking them for destruction by other immune cells. T helper cells assist in activating B cells, but the actual production of antibodies is mainly carried out by plasma cells. Memory B cells are involved in mounting a rapid and specific secondary response upon re-exposure to the same antigen. Macrophages play a role in phagocytosis and antigen presentation, but they are not the primary cells responsible for producing antibodies during the humoral immune response.

Correct Answer: B

Rationale: In a patient experiencing an acute asthma exacerbation with severe respiratory distress and hypoxemia, the most appropriate intervention is to initiate non-invasive positive pressure ventilation (NIPPV). NIPPV can help improve ventilation, decrease work of breathing, and correct hypoxemia by providing positive pressure to keep the airways open, reduce air trapping, and increase the elimination of carbon dioxide. This intervention can help improve oxygenation and reduce the need for invasive mechanical ventilation in patients with severe asthma exacerbations. Administering high-flow oxygen via nasal cannula alone may not provide enough support for patients with severe respiratory distress. Nebulized albuterol/ipratropium combination therapy and intravenous corticosteroid therapy are also important treatments for asthma exacerbations but are not the first-line interventions for patients with severe respiratory distress and hypoxemia.

Correct Answer: C

Rationale: In a pregnant patient with suspected pulmonary embolism (PE), the most appropriate imaging modality for evaluation is contrast-enhanced computed tomography (CT) pulmonary angiography. This imaging technique has been shown to be safe for the fetus when necessary, especially if the benefits of making a diagnosis outweigh the minimal risks associated with radiation exposure. It provides quick and accurate detection of PE with high sensitivity and specificity.

Correct Answer: A

Rationale: In this case, the patient is experiencing respiratory acidosis as indicated by the low pH (7.28), elevated PaCO2 (65 mmHg), and elevated HCO3- (30 mEq/L). The primary acid-base disturbance is respiratory acidosis due to the retention of carbon dioxide (PaCO2 >45 mmHg) leading to an increase in HCO3- as a compensatory mechanism to maintain pH within normal limits. The elevated HCO3- levels (metabolic compensation) are trying to counterbalance the increased PaCO2 levels (respiratory acidosis) by increasing bicarbonate to attempt to normalize the pH. Overall, the ABG analysis shows respiratory acidosis with metabolic compensation in this COPD patient with an acute exacerbation and severe dyspnea.

Correct Answer: D

Rationale: The clinical presentation of a patient with chronic kidney disease (CKD) presenting with weakness, anorexia, confusion, severe anemia, low reticulocyte count, elevated serum creatinine, and decreased erythropoietin levels is most consistent with renal failure-associated anemia. In CKD, the kidneys are unable to produce adequate amounts of erythropoietin, a hormone responsible for stimulating red blood cell production in the bone marrow. The decreased erythropoietin levels lead to a state of anemia, characterized by low hemoglobin levels and subsequent symptoms of fatigue and weakness. The anemia in renal failure is typically normocytic and normochromic. Additionally, the elevated serum creatinine in this patient is a hallmark of kidney dysfunction.