There are two main types of immunity.
Protecting the body from the invasion of foreign substances Role of Block... "mucosal immunity"
Attacks foreign substances to protect the body Role of Attack... "whole body immunity"

When foreign substances and pathogens invade ...
Mucosal immunity blocks the invasion of foreign substances.

It catches foreign substances with the mucous membrane to prevent them from entering the body and takes them out of the body.

On the mucosal surface, IgA antibody (immunoglobulin) made of protein reacts with pathogens (antigens) and suppresses movement.

IgA antibodies are especially exists in the intestine.

When a pathogen (antigen) breaks through mucosal immunity and invades the body from a wound or the surface of the body ...

Whole body immunity attacks foreign substances.

Cells that are in charge of innate immunity detect the invasion of foreign substances and come quickly.

Immune cells feed on the antigen. This is called phagocytosis .

Neutrophils rush to eat the antigen first, and macrophages and dendritic cells decompose the antigen by phagocytosis ...

Some of the degraded antigens are shown extracellularly. This is called antigen presentation . (Macrophages are mainly responsible for phagocytosis, and dendritic cells are mainly responsible for antigen presentation.)

Helper T cells receive antigen information by antigen presentation ...

Cytokines stimulate and activate killer T cells and B cells.

Stimulated B cells proliferate and differentiate to produce antibodies ...

It becomes an antibody-producing cell (plasma cell), produces antibodies, and secretes them into body fluids .

When the antigen and antibody specifically bind, a antigen-antibody reaction occurs, and the antigen is detoxified and its movement is suppressed.

When foreign matter is eliminated ...

Regulatory T cells (suppressor T cells) suppress the movement of active T cells and prevent runaway.

When B cells proliferate and differentiate, some become memory cells that store antibody information against antigens and remain in body fluids for a period of time.

Therefore, when the same antigen invades again, it causes a stronger antigen-antibody reaction faster than the first time, making it less likely to get the same disease.

This second and subsequent antigen-antibody reactions are called secondary responses.

Killer T cells destroy the infected cells.