Memory cells are responsible for:

Which immunoglobulin is the largest in size?

What percentage of lymphoid tissue in the human body is constituted by Mucosa-Associated Lymphoid Tissue $(MALT)$ (in $\%$)?

Read the given statements carefully and identify the incorrect statements.
$(1)$ In active acquired immunity,antibodies are directly injected into the body.
$(2)$ Vaccination is considered under passive acquired immunity.
$(3)$ The human body distinguishes between self and non-self with the help of $Tc$ cells.
$(4)$ Innate immunity consists of four types of barriers.

What are the two corollaries related to the immune system?

Which is the main physical barrier in our body?