What is an antibody?

The spleen is a large bean-shaped organ which primarily acts as a filter of the blood by trapping blood-borne microorganisms. Which of the following statements is correct regarding the spleen?

When pre-formed antibodies are injected into the body,it is called .........

Assertion $A$: Vaccination protects an individual against infection by specific pathogens.
Reason $R$: $B$ and $T$ memory cells produce antibodies in large quantities to neutralize the pathogen attack.
Which option is correct for Assertion $A$ and Reason $R$?

Secretion of interferon is which type of barrier?

Identify $X$ from the given figure.