it deals with the antigen and its type

1. Its foreign molecule which induce the immune system in the
body.
It stimulates the lymphocytes to produce the antibody.
T-cell and B-cell are the antigen presenting cells.

2. Its majorly classified into two types
1. Exogenous antigen.
 Endogenous antigen.
 And endogenous antigen is fatherly classified into 3 types
1. Heterogenic antigen.
2. Allogenic antigen.
3. Autologous antigen.

3. This type of antigen are enter from the outside of the body.
This antigen entering site are macrophages, dentric cells etc.
Example: virus, bacteria and fungi etc.

4. These type of antigen found inside the cytosol of the human
cells.
Example: viral protein, tumer protein etc.
It was in three types.

5. It also known as xenogenic antigen.
It is foreign molecules related with the tissue
transplantation and serology at the time entering
molecule are heterogenic antigen.

6. This type of antigen occurs only in the
individual species.
For example blood group antigen.

7. The antigen originate from the body it self is
autologous antigen.
Example: Thyroglobulin and DNA etc.