Immune Response to Levan

Abstract

Abstract Normal adult BALB/c mice immunized with bacterial levan (BL) produce antibodies that bind inulin and BL and that express cross-reactive idiotypes (IdX-G, IdX-A, IdX-B) found on inulin-binding myeloma proteins. In addition, such mice make anti-BL antibodies that fail to bind inulin and that do not express the IdX. Young BALB/c mice immunized with BL or with a variety of inulin conjugates fail to produce antibodies that bind inulin or express IdX although such mice immunized with BL do produce antibodies that bind BL. The late appearance of the capacity to produce IdX+ anti-inulin antibodies is most probably due to a delay in development or maturation of precursor cells rather than to some defect ascribable to the nature of the carrier molecule, to the presence of suppressor cells, or to a microenvironmental defect in the neonate. Thus, inulin determinants on a variety of carriers fail to stimulate the response of young mice; spleen cells from young mice transferred to adult C.B20 mice do not respond unless they have been in residence for 7 to 14 days before immunization; T cells from young mice do not suppress the response of adult BALB/c mice and adult spleen cells can mount a response when transferred into 1-week-old recipients. Furthermore, the polyclonal activator Nocardia water-soluble mitogen (NWSM) stimulates the appearance of anti-BL plaque-forming cells (PFC) but not of anti-inulin PFC in spleen cells from mice of 1 to 3 weeks of age, whereas spleen cells from 4-week-old and older mice develop both anti-BL and anti-inulin PFC in response to NWSM. A most provocative finding is the appearance in the serum of our nonimmunized young BALB/c mice of IdX-A+ molecules that lack IdX-G and -B and that do not bind to inulin or BL. The precursors of cells secreting these IdX-A+ molecules are interesting candidates for a “protoclone” from which precursors of IdX-G+, -A+, -B+ anti-inulin antibody-forming cells develop.