Final answer:
The root cause of immunological responses in the body is the immune system's ability to recognize and respond to foreign substances, or antigens.
Step-by-step explanation:
The root cause of all immunological responses in the body is the ability of the immune system to recognize and respond to foreign substances, known as antigens. When a foreign antigen enters the body, the immune system identifies it as non-self and triggers a series of immune responses to eliminate it. These responses can include the production of antibodies by B cells, the activation of T cells, and the release of inflammatory molecules to destroy the antigen.