In setting up a complement fixation test for antibody, the reactants should be added in what sequence?

Correct Answer: D

Rationale: The correct sequence for setting up a complement fixation test for antibodies is as follows: Ag + patient's serum + C (complement) / wait / + EA (erythrocyte antigen). This sequence ensures that the patient's serum containing antibodies is mixed with the antigen (Ag) first to allow for antibody-antigen binding. Then, complement (C) is added to the mix to activate the complement fixation process. Finally, erythrocyte antigen (EA) is added to observe any hemolysis indicating the presence of antibodies. This order is crucial for accurate test results. Incorrect choices: A: Incorrect sequence, as patient's serum should be mixed with Ag first. B: Incorrect sequence, as C should be added before EA. C: Incorrect sequence, as EA should be added last for hemolysis observation.

Correct Answer: C

Rationale: The correct answer is C: removing mature T cells from the graft. Graft-versus-host disease (GVHD) occurs when the donor's T cells attack the recipient's tissues. Removing mature T cells from the graft can reduce the risk of GVHD while preserving the graft's ability to engraft and function. Matching complement components (choice A) may help in other transplant scenarios but not specifically in reducing GVHD. Administering alpha interferon (choice B) is not a standard method for preventing GVHD. Removing pre-B cells (choice D) does not target the cells responsible for GVHD.

Correct Answer: B

Rationale: The correct answer is B because both antibody and receptor molecules have a specific shape that is essential for their specific functions. Antibodies bind to specific antigens, while receptors bind to specific ligands to initiate cellular responses. This specificity is crucial for their roles in the immune system and cell signaling pathways. Choices A, C, and D are incorrect because antibodies and receptors do not control transport through the cell membrane, remove wastes from the body, or speed up chemical reactions in cells. These functions are carried out by other molecules with different structures and mechanisms.

Correct Answer: B

Rationale: The correct answer is B: Unilateral, localized, nodular skin lesions. Herpes zoster, commonly known as shingles, is caused by the reactivation of the varicella-zoster virus, which initially causes chickenpox. This reactivation typically results in a painful rash with unilateral, localized, nodular skin lesions following a specific dermatome pattern. The rash consists of fluid-filled vesicles that eventually crust over. This presentation is distinct from genital herpes (Choice A), which manifests as vesicular rash in the genital region due to herpes simplex virus. Widespread red macules (Choice C) and small, painless ulcers (Choice D) are not characteristic of herpes zoster.

Correct Answer: B

Rationale: The correct answer is B because installing an electrostatic filter in the furnace can effectively reduce dust particles circulating in the home environment. Electrostatic filters are designed to capture smaller particles like dust, pollen, and pet dander, thus reducing allergen exposure. Incorrect choices: A: Installing curtains does not address the root cause of dust allergens and may even accumulate more dust than other alternatives. C: Vacuuming once a month is not sufficient to control dust allergens, as regular and thorough cleaning is necessary. D: Using feather pillows may exacerbate dust allergies as they can trap dust mites.