Effect of Treating Newborn Mice with Various Doses of Anti - A 48 Id Antibody on the Anti - BL PFC Response

BALB/c mice immunized with bacterial levan (BL), a /3(2---*6) fructosan with fl(2--*l) branched points, produce antibodies of two general types (1). One group of molecules is specific for inulin, which is a fl(2---* 1) fructosan, as well as for levan; such antibodies, which can first be detected in BALB/c mice at 28 d of age (2), express idiotypes (Id) that cross-react with those found on inulin-binding myeloma proteins (3). The second principal group of antibodies binds BL, but not inulin, and fails to express cross-reactive idiotypes (IdX) of anti-inulin antibodies (1); these can be elicited in l-d-old BALB/c mice after immunizat ion with BL (2). The Id found on myeloma proteins ABPC 48 (A48) and U P C 10 (UI0), which bind BL but fail to bind inulin, are generally not detected on anti-BL antibodies of BALB/c mice (3). However, in n u / n u BALB/c mice, pretreatment with ant i -El09 IdX antibodies before immunization with BL results in the occurrence of A48 Id + ant i -BL antibodies (4). This observation indicates that the A48 Id ÷ anti-BL response belongs to a normally silent fraction of the ant i -BL repertoire. This observation p rompted us to investigate the activation of A48 Id+-bearing clones in neonates after the administrat ion of anti-A48 Id antibodies. Our results indicate that the administrat ion of anti-A48 Id antibodies to 1-d-old BALB/c mice causes a substantial increase in the A48 Id ÷ component of the ant i -BL ant ibody response.