Write a note on lymphoid organs.

Lymphoid organs are the organs where the origin,maturation,and proliferation of lymphocytes occur.
The primary lymphoid organs are the bone marrow and thymus,where immature lymphocytes differentiate into antigen-sensitive lymphocytes.
After maturation,the lymphocytes migrate to secondary lymphoid organs such as the spleen,lymph nodes,tonsils,Peyer's patches of the small intestine,and the appendix.
The secondary lymphoid organs provide the sites for the interaction of lymphocytes with the antigen,which then proliferate to become effector cells.