Final answer:
The earliest B-cell precursor can be recognized by IgM receptors on the B-cell surface. These receptors bind to non-specific antigens and present them in combination with MHC-II. CD4+ T cells recognize this complex and induce the differentiation of the B-cell into a plasma cell.
Step-by-step explanation:
The earliest B-cell precursor can be recognized by the presence of IgM receptors on the B-cell surface. These receptors first recognize non-specific antigens and bind to them, leading to internalization of the antigen by phagocytosis. The processed antigen is then presented on the B-cell surface in combination with major histocompatibility complex-II (MHC-II), which is recognized by CD4+ T cells. The interaction between the B-cell and the CD4+ T cells induces the differentiation of the B-cell into a mature antibody-secreting plasma cell.