What haematological condition does this patient have? (75-year-old with septic shock, ARDS, bleeding, low platelets, elevated PT/APTT)

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: 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.

Correct Answer: C

Rationale: Rationale for Correct Answer (C): When spleen cells from a donor mouse are injected into a genetically dissimilar recipient mouse, it can lead to a graft-versus-host reaction. This is because the recipient's immune system recognizes the donor cells as foreign and mounts an immune response against them. In this case, since the donor mouse is of strain A and the recipient is an F1 hybrid of strains A and B, the genetic disparity is significant, leading to a higher likelihood of a strong immune response from the recipient against the donor spleen cells. Summary of Incorrect Choices: A: The spleen cells being destroyed is less likely as the recipient's immune system would typically recognize and respond to foreign cells rather than simply destroy them. B: Spleen cells surviving without any effect is unlikely because of the genetic disparity between the donor and recipient mice. D: Inducing tolerance of strain A grafts in the recipient is less likely as a strong immune response is expected due to the genetic differences between

Correct Answer: B

Rationale: The correct answer is B: Individuals of blood group type AB are 'universal recipients' of transfusions. This is because individuals with blood type AB have both A and B antigens on their red blood cells, making them compatible with all blood types during transfusions. Choice A is incorrect because Rh factor is separate from ABO blood group system. Choice C is incorrect because individuals with blood type AB do not have circulating anti-A or anti-B antibodies. Choice D is incorrect because haplotype refers to a set of genes on one chromosome, which is not directly related to blood group type.