Final answer:
Lymphocytes, including B cells and T cells, undergo selection and maturation in primary lymphoid organs, the bone marrow and thymus, respectively. They then migrate to secondary lymphoid organs like lymph nodes and the spleen, where they await antigen presentation to become activated. Once activated, B cells can differentiate into plasma cells and return to the bone marrow.
Step-by-step explanation:
Lymphocyte Migration from the Bloodstream to Secondary Lymphoid Organs
Lymphocytes, encompassing B cells and T cells, must first undergo a selection process that allows them to identify and distinguish self from non-self. For T cells, this maturation occurs in the thymus. The minuscule portion of cells that successfully complete this process exits the thymus to travel through the bloodstream and lymphatic system. They eventually migrate to sites of secondary lymphoid organs such as lymph nodes, spleen, and tonsils. Once localized in these secondary organs, these mature naïve lymphocytes await the presentation of specific antigens by Antigen-Presenting Cells (APCs) to become activated.
B cells, after maturing in the bone marrow, also move to the circulatory system and thereafter enter the lymphatic system where they can encounter pathogens. The primary lymphoid organs essential to this process include the bone marrow and thymus. Secondary lymphatic organs, which serve as activation sites for lymphocytes to mount adaptive immune responses, include lymph nodes, spleen, tonsils, and lymphoid nodules. Upon activation by antigens, B cells differentiate into plasma cells and leave the secondary organs to return to the bone marrow, where after a period of antibody secretion, they die due to their terminal differentiation.