Answer: Antibody molecules
Explanation:
The immune system is categorised into two functional systems:
-Innate (natural) immune system and
-Acquired (adoptive) immune system.
The acquired immune system plays a major role against all the microbes capable of producing diseases and they are classified into two namely: Humoral and cell mediated immunity. The humoral immunity involves the B cells and the production of antibodies which are specific to invading antigens of disease causing organisms.
Antibodies are molecules of the adaptive defence system that provides humoral immunity by circulating freely in the blood and lymph.
