Final answer:
Immature B cells undergo screening for self-reactivity before they migrate to the periphery, ensuring that they do not react against the body's tissues. This selection occurs in the bone marrow via mechanisms of both positive and negative selection. In contrast, T cells are screened in the thymus after migrating there from the bone marrow.
Step-by-step explanation:
Immature B cells are screened for self-reactivity before migration to the periphery. This process involves both positive and negative selection of B cells within the bone marrow to ensure the development of B cells that can respond to foreign antigens but not react against the body's tissues. The first step in this maturation process is the positive selection of B cells with functional receptors. Subsequently, negative selection mechanisms eliminate or render self-reactive B cells harmless by processes such as apoptosis, receptor editing, or induction of anergy.
Only after passing these selection processes in the bone marrow do immature B cells travel to the spleen for the final stages of their maturation, becoming naive mature B cells. This is contrasted with T cells, which migrate from the bone marrow to the thymus for their selection and maturation. In the thymus, T cells undergo a similar process where those expressing TCRs complementary to self-antigens are destroyed, contributing to the prevention of autoimmune responses.