Question

How is active humoral immunity achieved?

Answer 1

From successfully fighting off a disease.

Explanation:

Once your body has been infected with a disease (let's say the flu), B cell and T cell production gets ramped up to fend off the virus.

After the body rids off the infection, special cells called memory B cells and memory T cells that "remember" how to kill specifically the flu virus remain.

If the body gets infected with the same strain of the flu again, then the body's immune system will kill off the virus much better/quicker than the first time. This is called active humoral immunity.