Question

Consider the following statement with two blanks as A and B.

“______A_______ is a cellular barrier which directly kills _____B______ cells.

The correct option is

• A. A - Thrombocyte, B - bacterial
• B.
  A - RBCs, B - viral
  
• C. A - Basophil, B - cancer
• D. A - Natural killer cells, B - bacterial

Answer 1

The correct option is D A - Natural killer cells, B - bacterial

Cellular barriers are present in our body to resist infection or invasion by microorganisms. It is a part of natural immunity present in our body by birth itself. As the name suggests it include a group of cells as follows-

Natural killer cells are a type of lymphocytes (white blood cells) capable of attacking the target cells (tumour cells, bacterial and viral infected cells) without help from antibodies. They are able to attack and kill bacterial infected cells.

PMNL : Polymorphonuclear leukocytes (white blood cells with lobed nucleus) like neutrophils can attack and destroy bacteria, viruses which are circulating in the bloodstream. Basophils, a type of white blood cell, are involved in inflammations. They have granules with histamine, serotonin etc. which are released at the site of inflammation. They will not attack cancer cells.
Thrombocytes or platelets are present in blood, they help in coagulation of the blood at the site of wound or injury. It prevents the loss of blood due to injury. They are not involved in attacking or killing microorganisms.
Red blood cells are the major cells in the circulatory system. They help in transport of gases. They will not attack the viral cells.