After maturation, in primary lymphoid organs, the lymphocytes...

The primary lymphoid organs are bone marrow and thymus where immature lymphocytes differentiate into antigen-sensitive lymphocytes. After maturation, the lymphocytes migrate into secondary lymphoid organs like spleen, lymph nodes, Peyer's patches of small intestine and appendix. These secondary lymphoid organ provide the sites for interaction of lymphocytes with the antigen.