Je. Lima et al., Lymphocyte activation and cytokine production by Pisum sativum agglutinin (PSA) in vivo and in vitro, IMMUNOPHARM, 41(2), 1999, pp. 147-155
Mice spleen cells were incubated in vitro for 24 h with Pisum sativum agglu
tinin (PSA). The addition of these supernatants (SN) to macrophage cultures
induced the production of nitric oxide (NO) by these cells in a dose-depen
dent manner. NO release was blocked in the presence of IFN gamma antibodies
and partially inhibited by TNF alpha antibodies. The ability of PSA in ind
ucing the production of IFN gamma and TNF alpha by spleen lymphocytes was c
onfirmed assaying these cytokine levels in the SN, Spleen cells stimulated
in vitro with PSA were highly activated showing an increased expression of
the earlier activation marker, CD69, and a great proliferative response. On
the other hand, spleen cells obtained from mice treated with PSA 24 h earl
ier, did not produce significant levels of IFN gamma or TNF alpha when incu
bated in vitro and showed a significantly lower proliferation rate when pul
sed in vitro with PSA or Concanavalin A (ConA). The lower responsiveness to
mitogens was also evident after 48 and 72 h after the treatment in vivo wi
th the lectin, Nevertheless, the flow cytometric analysis of spleen lymphoc
ytes obtained from PSA-treared animals showed a high degree of activation i
n cells CD3(+), There was a decrease in the expression of L-selectin and VL
A-4, when compared to controls, in parallel with a significant increase in
the expression of CD69 and CD122 (IL-2R) in lymphocytes recovered from PSA-
injected animals. The data point to evidence that PSA induces immunomodulat
ory effects, activating spleen lymphocytes in vivo, which become unresponsi
ve to a second stimulation in vitro. (C) 1999 Elsevier Science B.V. All rig
hts reserved.