FREQUENCY OF B-CELLS IN NORMAL MICE WHICH RECOGNIZE SELF PROTEINS

The mechanism whereby the immune system avoids self-aggression is one of the central issues of Immunology. The discovery of natural autoanti bodies, mainly of IgM isotype, and of idiotypic interactions between a ntibodies indicates that elements of the immune system interact with s elf constituents and with themselves. Results of studies with soluble antibodies have indicated that the pool of circulating IgM represents the end result of a highly selective process of B cell activation and differentiation by self proteins resulting in the formation of a netwo rk. The objective of the present work was to determine the frequency o f self-reacting B cells in normal mice. We were able to detect B cells that recognize self proteins present in extracts of different organs in normal adult, 2-3-month old, BALB/c and C57BL/6 mice with an ELISA spot assay. About 1% of total IgM-secreting cells among small, LPS-sti mulated spleen cells reacted with organ extracts, whereas among large spleen cells the frequency was 5- to 10-fold lower. Immunization induc ed an increase in the frequency of IgM-secreting cells. The present re sults provide cellular evidence for the results of studies done at the serological level. The physiological role of these self-recognizing c ells, as well as their participation in autoimmune processes, remain t o be established.