Lymphoid Organs

Primary Lymphoid Organs                Secondary Lymphoid Organs
● It includes bone marrow and       ● The organs where lymphocytes
thymus where B-and T-cell                interact with the antigen and
lymphocytes mature and                   proliferate to become effector
acquire their antigen-specific.          cells, e.g., spleen, lymph nodes,
receptor.                                               tonsils, Peyer’s patches of small                                                                   intestine and appendix

Lymph nodes are small solid structures present at different points along the lymphaticsystem. They trap the microorganisms or other antigens that enter the lymph and tissuefluid. Antigens trapped in the lymph nodes activate the lymphocytes and produce an immune response.