Which of the following statements is NOT true? The SARS coronavirus

Correct Answer: C

Rationale: The correct answer is C because the statement that SARS coronavirus is also the causal agent of MERS is false. MERS (Middle East Respiratory Syndrome) is caused by a different coronavirus called MERS-CoV. SARS-CoV caused the 2003 epidemic with a 10% mortality rate, which aligns with statement A. Statement B is correct as SARS-CoV does cause an acute infection of the lungs known as acute respiratory distress syndrome. Statement D is also true as SARS-CoV is believed to have been transmitted from bats to civets and then to humans. Therefore, the incorrect statement is C.

Correct Answer: B

Rationale: The correct answer is B: Autism. The controversy surrounding the MMR vaccine and autism emerged from a fraudulent report that falsely claimed a link between the two. Numerous scientific studies have since debunked this association, confirming the safety of the MMR vaccine. Autism is a neurodevelopmental disorder with a complex etiology, involving genetic and environmental factors, but not vaccines. Choices A, C, and D are incorrect as there is no proven causal link between the MMR vaccine and multiple sclerosis, encephalitis, or epilepsy.

Correct Answer: D

Rationale: The correct answer is D because somatic hypermutation can lead to the formation of antibodies with higher affinity for the antigen by introducing point mutations in the variable regions of immunoglobulin genes. This process mainly occurs in the complementarity-determining regions (CDRs) of immunoglobulin heavy and light chain genes, which are critical for antigen binding. Somatic hypermutation takes place in the germinal centers of secondary lymphoid organs, where B cells undergo rapid proliferation and selection based on antigen binding affinity. Therefore, all the statements in choices A, B, and C are correct, making option D the right answer.

Correct Answer: B

Rationale: The correct answer is B: Linear. T cells recognize linear epitopes, which are sequences of amino acids displayed in a linear fashion on the antigen's surface. This recognition occurs through the T cell receptor binding to the linear epitope. Conformational epitopes (A) involve multiple amino acid residues brought together in a specific three-dimensional structure. Epitopes on the antigen surface (C) are correct, but not all T cell epitopes are necessarily on the surface. Epitopes buried inside the antigen (D) are not accessible to T cell receptors for recognition. Thus, the correct choice is B due to the linear presentation of epitopes for T cell recognition.

Correct Answer: B

Rationale: The correct answer is B because there are no reports of the Black Death dating back to 1000 B.C. The Black Death specifically refers to the pandemic outbreak of the bubonic plague in the 14th century. The first recorded pandemic of the Black Death occurred in the 14th century, not in 1000 B.C. The other choices are incorrect because A is true as the Black Death did devastate Europe in the 14th century, C is true as plague is still present in some countries, and D is true as plague can be treated with antibiotics if caught early.