B cell clones form

Correct Answer: D

Rationale: B cell clones become memory cells and plasma cells.

Correct Answer: C

Rationale: Cell-mediated immunity targets intracellular pathogens; T cells are 60-70% , humoral is adaptive , and NK cells are innate .

Correct Answer: C

Rationale: Toxoplasmosis causes 50% of CNS lesions; candidiasis is common but not specified, Mycoplasma isn't sentinel , and malignancy is 25-40% .

Correct Answer: A

Rationale: Affinity maturation refines antibody via antigen stimulation; recombination is earlier, switching changes class.