A young child presents with cervical adenitis and gingivostomatitis. History reveals recurrent pyogenic infections. Tests are done to determine leukocytosis and the presence of cell adhesion molecules. Which of the following is the most likely?

Correct Answer: C

Rationale: LAD impairs leukocyte adhesion, leading to recurrent pyogenic infections and poor wound healing.

Correct Answer: C

Rationale: A hapten is a small molecule that can bind to antibodies but cannot induce an immune response unless attached to a carrier protein.

Correct Answer: A

Rationale: Hyperacute rejection is mediated by preformed antibodies that bind donor antigens, triggering immediate graft damage.

Correct Answer: D

Rationale: B cells exhibit allelic exclusion, but the expression of maternal or paternal alleles varies between individuals, though typically only one allele is expressed per B cell.

Correct Answer: D

Rationale: Gamma interferon (IFN-γ) from Th1 cells activates macrophages, enhancing phagocytosis, making it the most accurate statement.