Am. Blum et al., Interleukin 12 and antigen independently induce substance P receptor expression in T cells in murine schistosomiasis mansoni, FASEB J, 15(6), 2001, pp. 950-957
Substance P (SP) regulates interferon-gamma (IFN-gamma) production through
interaction with the SP receptor NK1 (SPr) on T cells at sites of inflammat
ion. Using murine schistosomiasis, we evaluated whether SPr expression was
subject to immunoregulation. Splenocytes from schistosome-infected mice cul
tured for less than or equal to 18 h did not express SPr, as determined by
quantitative polymerase chain reaction assay. However, exposure to schistos
ome egg antigen (SEA) for less than or equal to4 h induced strong receptor
expression. Experiments using splenocytes fractionated with antibody-couple
d, paramagnetic beads showed that induction localized exclusively to T cell
s. Receptor protein expression was confirmed with Western blot. Interleukin
12 (IL-12) also induced strong T-cell SPr expression. Both SEA and IL-12 r
emained strong inducers of T-cell SPr in lymphocytes from the IL-12 (p40) a
nd IFN-gammaR doublel-knockout mouse, which suggested that SEA did not requ
ire IL-12 to induce SPr and that both worked independently of IFN-gamma. Sp
lenocytes from wild-type mice cultured with SEA and neutralizing anti-IL-12
monoclonal antibody (mAb) also showed SPr induction. However, anti-Ia mAb
inhibited SEA. induction of SPr. Thus, SPr is inducible on T cells. SEA ind
uces SPr through interaction with T-cell receptor (TCR), independently of I
L-12 and IFN-gamma. IL-12 induces SPr independently of TCR activation and I
FN-gamma expression. SP and its receptor, which regulate IFN-gamma producti
on, are probably part of the IL-12-Th1 circuit.