The substance produced by a cell in viral infection that can protect other cells from further infections is

In higher vertebrates,the immune system can distinguish self-cells and non-self. If this property is lost due to genetic abnormality and it attacks self-cells,then it leads to

Match the following barriers of innate immunity with their respective examples and select the correct option:

List-$I$ (Barrier)	List-$II$ (Example)
$A$. Physical barrier	$i$. Skin
$B$. Physiological barrier	$ii$. Interferons
$C$. Cellular barrier	$iii$. Mucus coating
$D$. Cytokine barrier	$iv$. Saliva in mouth

What is immunity based on?

Which type of innate immunity barrier is represented by the secretion of saliva from the mouth and tears from the eyes?

Which antibody,if present at birth,indicates that the fetus has been infected (intrauterine infection)?