7 research outputs found
Antigen-Independent Selection of T15 Idiotype During B-Cell Ontogeny In Mice
Precursors of B cells capable of responding to a T-independent form of phosphorylcholine
(PC) in splenic focus assays were detected in the spleens of neonatal mice as early as 4 days
after birth. The earliest anti-PC B cells were T15-. T15+ foci-forming B cells were first
detected 6 days after birth and expanded rapidly to constitute greater than 80% of the total
PC-specific foci by day 10. Injection of heat-killed S. pneumoniae (R36A) into neonatal mice
resulted in priming of the antibody response to PC, with an idiotype profile reflecting that
of precursors of foci-forming B cells at the time of antigen administration. Priming of 2-dayold
mice with 2 X106 and 2 X107 R36A induced a five- and ten-fold increase in the antibody
response to phosphorylcholine 6 to 8 weeks later. However, only 10 to 15% of the serum
antibodies expressed the normally dominant T15 idiotype. Doses below 2 x105 R36A showed
no detectable priming activity. PC-specific hybridomas derived from mice injected with
2 X107 R36A 2 days after birth lacked the idiotypic and molecular characteristics typical of
T15+ antibodies. Antibodies to phosphorylcholine, raised by immunization of 6-week-old
mice are normally protective against pneumococcal infection. However, serum antibodies
from mice treated with R36A 2 days after birth and responding to phosphorylcholine
following challenge with R36A at 6 weeks of age failed to protect against deliberate infection
with virulent S. pneumoniae. These observations imply that the antigen phosphorylcholine
does not play a role in the selective expansion and dominant expression of the T15 idiotype