Final Answer:
B cells are almost absent from bone marrow and lymphoid tissues in the bloodstream due to their role in adaptive immunity.
Step-by-step explanation:
The distribution of B cells is intricately regulated within the immune system. B cells primarily reside in specialized areas such as bone marrow and lymphoid tissues, where they undergo maturation and differentiation. Once mature, they are released into the bloodstream to patrol the body for pathogens. The apparent scarcity of B cells in the bloodstream is a result of their strategic positioning in these primary immune organs. This segregation allows B cells to efficiently carry out their adaptive immune functions, including antibody production and antigen recognition, within the specialized microenvironments of the bone marrow and lymphoid tissues.