What is the medical term for an abnormal accumulation of blood in a tissue or organ?

Correct Answer: A

Rationale: The correct answer is A: Hematoma. A hematoma is an abnormal collection of blood within tissues. This occurs due to broken blood vessels and can lead to swelling and localized pain. Thrombosis (B) is the formation of a blood clot within a blood vessel, not an accumulation of blood in tissue. An embolus (C) is a blood clot that travels through the bloodstream and gets lodged in a blood vessel. Hemorrhage (D) refers to the excessive bleeding from blood vessels. In this case, the most appropriate term for an abnormal accumulation of blood in a tissue is hematoma.

Correct Answer: C

Rationale: The correct answer is C because NADPH oxidase is not constitutively expressed as a complex of 5 subunits in unstimulated cells. Instead, it is assembled and activated upon stimulation, such as during the respiratory burst following phagocytosis. Choice A is correct as NADPH oxidase is indeed involved in the respiratory burst. Choice B is correct as mutations in NADPH oxidase subunits lead to impaired pathogen killing and recurrent infections. Choice D is correct as NADPH oxidase controls the production of reactive oxygen species.

Correct Answer: C

Rationale: The correct answer is C because B cell receptors, known as antibodies, are Y-shaped proteins with two identical antigen-binding sites. This feature allows B cells to bind to specific antigens with high specificity. Each B cell receptor can bind to a unique antigen, leading to the initiation of an immune response. Choice A is incorrect because B cell receptors can be secreted as antibodies to target antigens outside the cell. Choice B is incorrect because B cell receptors recognize antigens directly, not in combination with MHC molecules. Choice D is incorrect because B cells primarily recognize specific antigens rather than general PAMPs associated with pathogens.

Correct Answer: B

Rationale: Correct Answer: B - Hematopoietic stem cells are not typically found within secondary lymphoid tissues because they are located in the bone marrow where they give rise to various blood cells. In contrast, secondary lymphoid tissues like lymph nodes and spleen primarily consist of mature immune cells and support immune responses. Naïve lymphocytes (A), dendritic cells (C), and antigens (D) are commonly found in secondary lymphoid tissues as they play crucial roles in the immune response.

Correct Answer: B

Rationale: Step 1: Memory response produces antibodies of higher affinity due to affinity maturation. Step 2: Memory response involves class switching, leading to production of IgG, IgA, and IgE. Step 3: IgM is predominant in primary response, but memory response shifts towards other classes. Summary: Choice B is correct as memory response produces antibodies of higher affinity and different classes. Choices A and C are incorrect as memory response does not typically result in more IgM or lower affinity antibodies. Choice D is incorrect as only choice B is accurate.