Question

The type of immunity that is present at the time of birth in humans is:

• A. None of these
• B. Both of these
• C. Acquired immunity
• D. Innate immunity

Answer 1

Answer: (D)

The innate immune system, also known as non-specific immune system, is the first line of defence. It comprises the cells and mechanisms that defend the host from infection by other organisms in a non-specific manner. This means that the cells of the innate system recognize and respond to pathogens in a generic way. Innate Immunity is present at the time of birth. Innate immunity consists of four types of barriers.
$\cdot$ Physical barriers: Skin on our body is the main barrier which prevents entry of the micro-organisms. Mucus coating of the epithelium lining the respiratory, gastrointestinal and urogenital tracts also help in trapping microbes entering our body.
$\cdot$ Physiological barriers: Acid in stomach, saliva in the mouth, tears from eyes all prevent microbial growth.
$\cdot$ Cellular barriers: Certain types of leukocytes (WBC) of our body such as polymorph nuclear leukocytes (PMNL-neutrophils) and monocytes and natural killer cells in the blood as well as macrophages in tissues can phagocytise and destroy microbes.
$\cdot$ Cytokine barriers: Virus-infected cells secrete proteins called interferon which protect non-infected cells from further viral infection.