Which of the following is responsible for cell-mediated immunity?

$A$ mammal born without a thymus gland is unable to produce which of the following?

$A$ - The vaccines generate memory $B$ and $T$ cells. $R$ - In vaccination,activated pathogens are introduced into the body.

Identify the correct statements from the following:
$(i)$ The skin is the main physical barrier.
$(ii)$ Mucus coating of the epithelium lining the respiratory,gastrointestinal,and urogenital tracts is a physiological barrier.
$(iii)$ $IgA, IgM, IgE, IgG$ are types of $T$-cells.
$(iv)$ The primary immune response is very intense.

Identify the cell that enables the human body to distinguish between self and non-self.

In higher vertebrates, the immune system can distinguish between self and non-self cells. Due to genetic or other unknown reasons, the immune system sometimes loses this property and starts attacking self-cells, resulting in: