You learned in the previous lesson that T cells require two independent signals to become activated. When T cells are activated, they acquire effector functions and begin to proliferate. This two-signal mechanism prevents the expansion of self-reactive effector T cells. Similarly, B cell receptor signaling alone is not sufficient to activate B cells. B cells require assistance from helper T cells to become activated by monovalent protein antigens and gain certain immune functions. What changes do you suspect will occur to B cells when they are activated by protein antigen and receive T cell help? (Select all that apply.) 1) They will generate memory cells that can respond to a subsequent exposure to antigen. 2) Their immunoglobulin genes will be mutated in a way that alters antigen affinity. 3) The isotype of their immunoglobulin (Ig) genes will change. 4) They will proliferate and expand. 5) They will secrete antibodies..