Which of the following types of antibodies activates $B$-cells?

In the case of tetanus,a patient is directly injected with antitoxins. This type of immunity is called .........

Interferons curb the infection of:

If you suspect a major deficiency of antibodies in a person,to which of the following would you look for confirmatory evidence?

The cells which directly attack and destroy the antigens are known as

Which of the following barriers is $NOT$ included in innate immunity?