Question

Identify the first line of defence from the options given.

• A. Secretions of skin
  
• B. Macrophages
  
• C. Lymphocytes
  
• D. Inflammatory response

Answer 1

The correct option is A Secretions of skin


The various organs, chemicals and reactions occurring in our body that help in defending pathogens and toxins is called the immune system. Body has three lines of defences to fight against diseases. They are the first, second and the third line of defence.

First line of defence : It includes the physical barriers and the secretions. Skin, mucous membranes, lysozyme in tears, HCl in stomach, oil on the skin etc., include the first line of defence. It prevents the entry of pathogens.

Second line of defence : Once the pathogen crosses the first line of defence they will be encountered by the second line of defence. It includes the cellular barriers (phagocytes, neutrophils, eosinophils), fever, inflammatory response etc. They are also non specific.

Third line of defence : It is a pathogen specific immune response against the pathogen. Lymphocytes, memory cells are mainly involved in this. It is otherwise called adaptive /acquired immunity.