Innate immunity refers to all those defence elements with which a person is born and are always available to protect the body. Macrophages form part of the cellular barrier.
The cellular barrier includes the following specialized cells:
(i) Polymorphonuclear leucocytes.
(ii) Monocytes.
(iii) Natural killer lymphocytes and
(iv) Macrophages - these cells phagocytose and destroy the invading microbes.