I. Nicolasgaulard et al., EFFECT OF THE PARASITE ENZYME, HYPODERMIN-A, ON BOVINE LYMPHOCYTE-PROLIFERATION AND INTERLEUKIN-2 PRODUCTION VIA THE PROSTAGLANDIN PATHWAY, Immunology, 85(1), 1995, pp. 160-165
The immune function of cattle infected with a primary infestation of H
ypoderma lineatum is impaired during the first instar migration of the
larvae. Hypodermin A (HA) is an enzyme secreted by the larvae that is
implicated in immunosuppression. The response of bovine peripheral bl
ood mononuclear cells (PBMC) to HA was examined in this study. HA bloc
ked their proliferation in response to phytohaemagglutinin (PHA) and i
ts effect was enhanced when cells were preincubated with HA before act
ivation. This suggests that HA affects the lymphocyte commitment to bl
astogenesis during the early stages of their activation. HA also markl
y reduced the production of interleukin-2 (IL-2) in PHA-stimulated bov
ine PBMC cultures. Furthermore, indomethacin, which inhibits prostagla
ndin (PG) synthesis, blocked the immunosuppressive effect of HA on the
PBMC proliferative response. The concentration of PGE(2) in medium of
PBMC or PMA-stimulated monocyte cultures was increased by incubation
with HA, Thus, the HA appeared to act by reducing IL-2 production via
a prostaglandin-dependent pathway.