The injection of serum from a horse,which has been repeatedly injected with cobra venom,into a person bitten by a cobra results in:

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

Assertion: Interferons are effective against viruses.
Reason: Proteins which can be synthesized only by genetic engineering are effective against viruses.

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.

How many types of antibodies are produced in our body?

Which of the following cells are involved in the defence mechanism of the body?