Glycosylation-inhibiting factor (GIF) is a 13-kDa cytokine secreted from T
cells. Administration of bioactive recombinant GIF inhibits IgG1 and IgE Ab
responses in vivo. Treatment of B cells with the cytokine reduces the secr
etion of IgG1 and IgE induced by LPS and IL-4. To examine the effect on cog
nate T-B interaction, GIF was added to low-density B cells from MD4 transge
nic (Tg) mice, which express B cell receptor specific for hen egg lysozyme
(HEL). The B cells were subsequently pulsed with HEL-OVA conjugate and cult
ured with OVA-specific naive CD4 T cells from DO11.10 Tg mice. Treatment of
Ag-presenting B cells with GIF reduced expansion and IL-2 secretion of nai
ve T cells and rendered them hyporesponsive to antigenic restimulation, res
ulting in 50-95% reduction of IL-4 and IFN-gamma secretion upon restimulati
on with Ag. GIF dramatically inhibited Th effector generation when it was a
dded to B cells before pulsing with HEL-OVA, whereas it showed little to no
effect when added after B cells were pulsed with Ag. GIF was more effectiv
e when B cells from MD4 Tg mice were pulsed with HEL-OVA than when they wer
e pulsed with OVA. This cytokine did not affect Th effector generation when
B cells or irradiated splenocytes pulsed with OVA(323-339) peptide stimula
ted naive DO11.10 T cells. Confocal microscopy revealed that GIF inhibited
internalization of HEL by B cells from MD4 Tg mice. Therefore, the cytokine
may regulate early steps of Ag presentation involving B cell receptors to
diminish Th effector generation from naive CD4 T cells.