Which species of protozoa can cause relapses of malaria? (Choose one)

Correct Answer: B

Rationale: The correct answer is B: P. ovale. P. ovale can cause relapses of malaria due to the presence of dormant liver stages (hypnozoites) that can reactivate weeks to years after the initial infection. P. falciparum, P. malariae, and P. knowlesi do not have hypnozoites and therefore do not cause relapses. P. falciparum is known for its severe manifestations, P. malariae has a long incubation period but does not cause relapses, and P. knowlesi mainly infects monkeys and rarely causes human malaria.

Correct Answer: D

Rationale: The correct answer is D (bovine serum albumin). Bovine serum albumin can act as a carrier protein, allowing hapten (penicillin) to bind and form a complex, triggering an immune response. This complex induces memory B cells, leading to a secondary response upon re-exposure to penicillin. Penicillin alone (choice A) is a hapten and cannot induce a secondary response without a carrier protein. Penicillin bound to egg albumin (choice B) is specific to egg albumin, not penicillin, and would not generate a response to penicillin. Egg albumin (choice C) is a protein unrelated to penicillin. Bovine serum albumin (choice D) is the correct carrier protein for penicillin in this context.

Correct Answer: B

Rationale: The correct answer is B: increased numbers of severe bacterial infections. Severely reduced C3 levels indicate a deficiency in the complement system, which plays a key role in immune defense against bacteria. Without C3, the ability to opsonize bacteria and enhance phagocytosis is impaired, leading to an increased susceptibility to severe bacterial infections. The other choices are incorrect because low gamma globulin levels are associated with antibody deficiencies, severe viral infections are typically more common with T-cell deficiencies, and hemolytic anemia is linked to issues with red blood cell destruction rather than bacterial infections.

Correct Answer: A

Rationale: The correct answer is A: Mu chain. During B lymphocyte maturation, the first immunoglobulin heavy chain synthesized is the Mu chain. This is because the Mu chain is the first heavy chain isotype expressed during early B cell development. The Mu chain combines with the surrogate light chain to form the pre-B cell receptor, which is essential for signaling in pre-B cells. The Mu chain is later replaced by other heavy chain isotypes such as gamma, epsilon, and alpha during B cell differentiation. Therefore, the Mu chain is the correct answer as it is the initial heavy chain produced in B cell maturation. Choices B, C, and D are incorrect because they represent heavy chain isotypes that are expressed at later stages of B cell development and differentiation.

Correct Answer: D

Rationale: The correct answer is D because minor histocompatibility antigens can induce immune reactions leading to rejection in transplantation. These antigens are derived from genetic variations, not detected by antibodies and complement (A), controlled by genes outside the major histocompatibility complex (B), and are important in transplantation as they contribute to rejection responses (C).