Introduction There are two primary lymphoid organs in humans including the login to view 4 more bullets They serve as the site of adaptive immune cell maturation steps such as login to view 8 more bullets Abnormalities in primary lymphoid tissue can result in login to view 4 more bullets Bone Marrow Bone marrow is the site of pluripotent hematopoietic stem cells that can login to view 17 more bullets Bone marrow also serves as the site of B-cell maturation where login to view 2 more bullets Thymus This photomicrograph shows a hassall corpuscle, which is a characteristic feature of the inner medulla of the thymus and is composed of epithelial reticular cells. The thymus is a primary lymphoid organ that is login to view 4 more bullets The thymus serves as the site of T-cell maturation where login to view 2 more bullets The thymus is composed of several regions including login to view 10 more bullets Abnormalities Abnormal development of primary lymphoid organs can lead to login to view 16 more bullets