A 20-year-old woman presents with sudden onset of severe lower abdominal pain and missed menstrual periods for the past two months. She has a positive urine pregnancy test. On transvaginal ultrasound, an empty uterus is visualized, and there is fluid in the cul-de-sac. Which condition is most likely to be responsible for these findings?

Correct Answer: B

Rationale: The correct answer is B: Ectopic pregnancy. In this scenario, the combination of missed periods, positive pregnancy test, and empty uterus on ultrasound with fluid in the cul-de-sac is highly suggestive of an ectopic pregnancy. Ectopic pregnancy occurs when the fertilized egg implants outside the uterus, commonly in the fallopian tube. The presence of fluid in the cul-de-sac indicates possible blood from a ruptured ectopic pregnancy, causing the severe lower abdominal pain. Ovarian cyst rupture (A) typically presents with less severe pain. Septic abortion (C) would present with signs of infection and products of conception in the uterus. Ovarian torsion (D) would present with acute onset of unilateral lower abdominal pain and a palpable adnexal mass, not fluid in the cul-de-sac.

Correct Answer: C

Rationale: The correct answer is C: Macrophages. Macrophages are antigen-presenting cells that engulf pathogens and present their antigens to T cells, initiating an immune response. They express major histocompatibility complex (MHC) molecules necessary for T cell recognition. B cells also present antigens but primarily to B cells for antibody production. NK cells are involved in killing infected cells, not antigen presentation. Eosinophils are mainly involved in allergic responses and defense against parasites, not antigen presentation.

Correct Answer: A

Rationale: The correct answer is A: Loss of self-tolerance. This is because autoimmune diseases result from a breakdown in the immune system's ability to distinguish between self and non-self antigens, leading to the production of antibodies against self-antigens. When self-tolerance is lost, immune cells mistakenly target the body's own tissues, causing tissue damage and inflammation. Choice B (Failure of innate immunity) is incorrect because autoimmune diseases are primarily driven by adaptive immunity rather than innate immunity. Choice C (Defective T cell activation) is incorrect as T cells play a critical role in the immune response to self-antigens in autoimmune diseases. Choice D (Impaired phagocytosis) is incorrect as phagocytosis is a mechanism primarily involved in the removal of pathogens, not in the development of autoimmune diseases.

Correct Answer: B

Rationale: The correct answer is B: IgA. In multiple myeloma, there is a proliferation of abnormal plasma cells, leading to a decrease in normal antibody production. IgA is the most abundant immunoglobulin in mucosal secretions and plays a crucial role in mucosal immunity. Therefore, a deficiency in IgA is common in patients with multiple myeloma. IgG is the most abundant immunoglobulin in the blood and is typically less affected in multiple myeloma. IgM is the first antibody produced in response to an infection and is less likely to be deficient in this case. IgE is primarily involved in allergic responses and is not typically affected in multiple myeloma.

Correct Answer: D

Rationale: The correct answer is D: Bronchodilator therapy. Bronchodilators help to relax and open up the airways, which can improve airflow and reduce symptoms such as cough, sputum production, and dyspnea in patients with chronic bronchitis. This intervention can help manage the patient's symptoms and improve their quality of life by making it easier for them to breathe. A: Smoking cessation counseling is important for overall management of chronic bronchitis, but it does not directly address the patient's current symptoms. B: Oral antibiotic therapy may be indicated if there is evidence of a bacterial infection, but it is not the first-line treatment for managing chronic bronchitis symptoms. C: Home oxygen therapy may be necessary for patients with severe hypoxemia, but it is not typically the first intervention for managing symptoms of chronic bronchitis without evidence of significant oxygen desaturation.