When the immune system of host are exposed to antigen and produces antibodies it is called as ______.

Solution

When the immune system of the host is exposed to antigen and produces antibodies it is called humoral immunity. When an antigen (Bacteria, virus or any other pathogen) enters the body the host cells i.e B lymphocytes(a type of WBC) are stimulated to release antibodies which cause the death of the pathogen. Humoral immunity is so named because it involves substances found in the humour or body fluids.