Hitoshi Mitsuzumi, Makoto Kusamiya, Takafumi Kurimoto and Itaru Yamamoto
(*)
Department of Immunochemistry, Faculty of Pharmaceutical Sciences, Okayama
University, Okayama 700-8530, Japan
(*) To whom correspondence should be addressed.
Abstract: To gain a better understanding of the possible mechanisms
by which a stable form of ascorbate, ascorbic acid 2-glucoside (AA-2G),
as an ascorbate source, augments antibody responses, we examined whether
AA-2G enhances the anti-sheep-red-blood-cell (SRBC) plaque-forming cell
(PFC) responses elicited with distinct interleukins that provide signals
for B-cell proliferation and differentiation in cultured murine T-cell-depleted
splenocytes. The anti-SRBC PFC responses were markedly reduced by T-cell
depletion; and additions of the concanavalin A-stimulated murine splenocytes
supernatant (CAS) or interleukin (IL)-1beta, IL-2, IL-5, IL-4 or IL-6 to
the culture limitedly restored the immune responses. AA-2G synergistically
stimulated the anti-SRBC PFC responses in the presence of IL-1beta-, IL-2,
IL-5 or CAS, IL-1beta among these cytokines being most highly affected.
However, it failed to enhance the PFC responses elicited by IL-4 or IL-6.
Repeated additions of ascorbic acid (AsA) during experimental periods could
also produced the enhancing effect, but a single addition of the vitamin
did not, because of its instability in the medium. It was shown that exposure
to IL-1beta, IL-2 or IL-5 must be done at early times after antigen stimulation
of the cells to support their optimal responses and that AsA exerted its
effect on day 2 and day 3 after the start of culture. These results suggest
that AsA may up-regulate the in vitro IgM antibody responses in a cytokine-dependent
manner.
Keywords: Ascorbic acid, Ascorbic acid 2-glucoside, Antigen-specific
antibody response, Interleukin, T-cell-depleted splenocyte