CD5(+) B-CELLS AND THE IMMUNE-SYSTEM

The CD5+ B-cell population is prominent in early life and may play a k ey role in the ontogeny of the immune system. Transplantation studies in mice are in support of CD5+ B cells as a separate lineage from CD5- B cells. In both mice and men there is evidence in favour of CD5 bein g an activation antigen rather than a lineage marker, but the jury is still out! The frequency of CD5+ B cells appears to be under genetic i nfluence. CD5+ B cells are receptive to many cytokines including IL-2 and IL-5 and themselves produce a number of cytokines especially IL-10 . The function of the CD5 molecule on B cells is presently unknown but it might be involved in interaction with CD72 on other B cells. CD5B cells generally utilise minimally mutated germ-line genes and produc e low avidity auto- and polyreactive antibodies (natural antibodies) g enerally of the IgM class.