Vaccination against measles means.........

Define the following terms: Antigen and Lymphoid organs.

Which barrier of innate immunity is represented by saliva in the mouth and tears in the eyes?

Where are $H_{2}L_{2}$ molecules found in the body?

Person '$A$' cannot step out of his house. He has to spend his entire life in sterile isolation; otherwise, he would quickly contract a fatal infection. This person has almost no effective immune system. This disease is also called '$baby$ $in$ $a$ $bubble$ $syndrome$'. Identify the disease this person '$A$' is suffering from.

Identify the odd one out from the following.