Question

What specific challenge does  Trypanosoma brucei present to the immune system?

		It frequently changes its antigens, staying one step ahead of the host's antibody response.
		It specifically attacks B lymphocytes preventing activation and antibody production.
		It specifically attacks T lymphocytes preventing their activation and crippling the cell-mediated immune response.
		Its antigens are not recognized by B and T lymphocytes so these host defense cells don't respond to the infection.

Answer 1

Trypanosoma brucei is a parasite that is carried by tsetse fly and causes sleeping sickness in human (host). This parasite can evade the immune system by changing its surface properties or antigens in a very shorter duration. Thus, the immune system in unable to catch up with the speed at which new strains appear and the infection persists.

Hence, the correct choice should be:

The specific challenge does  Trypanosoma brucei present to the immune system :

(a) It frequently changes its antigens, staying one step ahead of the host's antibody response.