HUMAN CD5+ (B1) B-CELLS IN HEALTH AND DISEASE

CD5 B cells (B1 cells) are the first B cells to be produced during ontogeny and usually utilise minimally mutated germ-line genes. They are mainly of the IgM class but may also express IgG and IgA. They produce low avidity auto and polyreactive antibodies (natural antibodies). There is evidence for and against B1 cells being a separate lineage. B1 cells probably play a role in setting up the idiotype network, antigen presentation and tolerance induction. Their relative importance of each of these different functions in maintaining an effective normal immune system is unclear. Chronic lymphocytic leukemia is a malignancy of the B1 population and Rheumatoid Arthritis probabLy represents an abnormal antigen-driven maturation of specific self-reactive anti-IgGFc clones. Since B1 cells are regulated by cytokines, other autoimmune diseases including some organ specific diseases where there is an increase in CD5 B cells, may represent abnormal cytokine regulation.