J. Matsunaga et al., Regulation of lymphocyte proliferation by eosinophils via chymotrypsin-like protease activity and adhesion molecule interaction, BR J PHARM, 130(7), 2000, pp. 1539-1546
1 We investigated the regulatory mechanisms responsible for release of eosi
nophil cationic protein (ECP) from eosinophils activated by platelet-activa
ting factor (PAF) and monitored intra-cellular pH (pHi) changes using a pH-
sensitive fluorescent probe. We also explored the mechanisms by which eosin
ophils suppress T-lymphocyte proliferation induced by phytohaemagglutinin (
PHA). In these experiments, a separated culture to investigate the ECP-medi
ated pathway and a coculture to identify the adhesion molecules involved in
eosinophil-lymphocyte interactions were employed.
2 Chymostatin (1 x 10(-6) M) inhibited ECP release by about 50% via stimula
tion by PAF or recombinant interleukin 5(rIL-5) plus IgG.
3 PAF (1 x 10(-7) M) raised eosinophil pHi from 6.9 to 7.3 within 20 a and
pretreatment of these cells with chymostatin (1 x 10(-6) M), but not with l
eupeptin or E64-d, completely prevented this increase.
4 Calcium ionophore A23187 (1 x 10(-7) M) induced ECP release and raised pH
i to within a range similar to that of PAF, however, chymostatin had no eff
ect on either.
5 Chymostatin reversed ECP-mediated suppression of PHA-induced T-lymphocyte
proliferation in separated cultures, but not in cocultures.
6 In coculture, eosinophils exhibited the same level of suppression of both
CD4+ and CD8(+) T-cell proliferation in response to PHA.
7 Monoclonal antibodies against CD11a, CD18 and CD54, but not CD11b, restor
ed eosinophil suppression of T-lymphocyte proliferation which was chymostat
in-resistant in coculture.
8 Eosinophils were unable to suppress the proliferative response to lymphoc
ytes to anti-CD3 stimulation.
9 In conclusion, chymostatin specifically inhibited both the eosinophil pHi
increase and ECP release induced by PAF. Eosinophils regulate PKA-induced
T-lymphocyte proliferation via the ECP-mediation associated with chymotryps
in-like protease activity. These cells also control interactions with lymph
ocyte between adhesion molecules, CD11a, CD18 and CD54.