M. Perez-melgosa et al., Cutting edge: CD40 ligand is a limiting factor in the humoral response to T cell-dependent antigens, J IMMUNOL, 163(3), 1999, pp. 1123-1127
CD40 ligand (CD40L) plays a crucial role in T cell-dependent B cell respons
es, but whether its abundance is a limiting factor in their development is
unclear. This question was addressed in transgenic mice expressing the muri
ne CD40L gene under the control of the IL-a-promoter (CD40Ltg(+)). The frac
tion of activated T cells from the CD40Ltg(+) mice with detectable levels o
f surface CD IOL was modestly greater (1.1- to 2-fold) than littermate cont
rols and paralleled an similar to 1.8-fold increase in CD40L mRNA abundance
. In response to trinitrophenol (TNP)-keyhole limpet hemocyanin and tetanus
/diphtheria vaccine, CD40Ltg(+) mice developed higher titers of high-affini
ty IBG and IgG1 Ab than wild-type mice. In contrast, the Ab response of CD4
0Ltg(+) and control mice was similar in response to the T-independent Ag TN
P-Ficoll, These results suggest that a modest increment in expression of CD
40L accelerates the development of T-dependent responses, and that CD40L pl
ays a limiting role in the induction of high-affinity Ab and Ab-class switc
hing.