The maximum number of erythrocytes generated by one Multipotential Stem Cell is:

Correct Answer: D

Rationale: The correct answer is D: 16. A Multipotential Stem Cell can differentiate into various blood cell types, including erythrocytes. Through the process of erythropoiesis, each Multipotential Stem Cell can produce up to 16 erythrocytes. This is achieved through several stages of cell division and maturation. Choice A (8) is incorrect because the number of erythrocytes produced is greater. Choice B (1) is incorrect as a Multipotential Stem Cell can differentiate into multiple cells. Choice C (12) is also incorrect as the maximum number of erythrocytes produced is 16.

Correct Answer: C

Rationale: The correct answer is C: Disseminated intravascular coagulation (DIC). In septic shock, the body's response can lead to widespread activation of clotting factors, causing both clotting and bleeding. Low platelets and elevated PT/APTT are common in DIC due to consumption of clotting factors and platelets. Thrombotic thrombocytopenic purpura (A) presents with microangiopathic hemolytic anemia, not typical in this case. Hemophilia (B) is a genetic disorder resulting in specific clotting factor deficiencies, not consistent with the patient's presentation. Von Willebrand disease (D) is a deficiency in vWF, leading to mucosal bleeding, not the systemic coagulopathy seen in DIC.

Correct Answer: B

Rationale: The correct answer is B because class II MHC proteins on donor cells are recognized by helper T cells, leading to the activation of cytotoxic T cells which then kill the donor cells. This process is crucial in graft rejection as it triggers an immune response against the foreign cells. Choice A is incorrect because class II MHC proteins are not receptors for interleukin-2. Choice C is incorrect as class II MHC proteins do not induce the production of blocking antibodies. Choice D is incorrect because class II MHC proteins do not induce IgE production, which is involved in allergic reactions, not graft rejection.

Correct Answer: C

Rationale: Complement fixation refers to the binding of complement components by antigen-antibody complexes. This process involves the activation of the complement pathway, leading to the formation of the membrane attack complex and subsequent lysis of target cells. Choice A is incorrect as it describes opsonization, not complement fixation. Choice B is incorrect as it refers to heat inactivation of complement. Choice D is incorrect as it does not involve complement fixation but rather describes the interaction of C3a with mast cells.

Correct Answer: C

Rationale: The correct answer is C: 1 week. Firstly, after initial exposure to an antigen, it takes time for the immune system to recognize and mount a response. This is known as the lag phase. Next, B cells need to be activated, differentiate into plasma cells, and start producing antibodies. This process typically takes a few days. Finally, the antibodies need to reach detectable levels in the blood, which usually occurs around 1 week post-exposure. Choices A, B, and D are incorrect because 12 hours is too short for the immune response to fully develop, 3 days may be sufficient for antibody production but not yet detectable levels, and 3 weeks is longer than necessary for detectable levels to be reached in a primary immune response.