The immune system consists of two main parts or system. One system works 24/7 and protects your regardless of what type of microorganism is encountered. This system is called the system. The other system requires recognition of the invader to react and begin to fight back an infection. This is called the system.

Part A. The Innate immune system

Part B. The adaptive (or active) immune system

Explanation:

The immune system refers to the organs, tissues cells and proteins which work together to protect the body from harmful invaders that cause disease such as micro-organisms like viruses, bacteria, etc.

Organs and tissues that form part of the immune system include the thymus and bone marrow, lymph nodes and vessels, spleen, and skin.

The main immune cells are the white blood cells, also called leukocytes. Some types of white blood cells, called phagocytes engulf invading organisms. Others called lymphocytes  help the body remember the invaders and destroy them.  The two kinds of lymphocytes are B lymphocytes and T lymphocytes, whose name depend on where they mature. Lymphocytes start their life in the bone marrow and either stay there and mature into B cells, or go to the thymus gland to mature into T cells.

The immune system consists of two main parts or system.

answer: they produce more slow than unicellular organisms.