Difference Between Primary Lymphoid Organs and Secondary Lymphoid Organs

Primary Lymphoid Organs (Example: Thymus, Bone marrow, Bursa of Fabricius)

1. The lymphoid stem cells proliferate, differentiate and mature

2. Contain either B cells or Tcells

3. Antigen cannot enter  in

4.They atrophy with age

Secondary Lymphoid Organs ( Example: Spleen, Lymph nodes, Peyers patches, Tonsils)

1. The lymphoid cells become functional

2. Contain both T and B cells.

3. Antigen enters in and stimulates the lymphoid cells

4. They increase in size with age