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

In $T$-lymphocytes,what does the letter '$T$' stand for?

Antivenom against snake poison contains

The immunity developed by a child after an attack of measles is . . . . . . immunity.

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.

$A$ substance (low molecular weight protein) produced by host cells in response to viral infection that protects other cells against further viral infection is: